text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Copyright (C) 2008 Oracle.  All rights reserved.
   */
  
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/blkdev.h>
  #include <linux/list_sort.h>
  #include <linux/iversion.h>
  #include "misc.h"
  #include "ctree.h"
  #include "tree-log.h"
  #include "disk-io.h"
  #include "locking.h"
  #include "print-tree.h"
  #include "backref.h"
  #include "compression.h"
  #include "qgroup.h"
  #include "block-group.h"
  #include "space-info.h"
  #include "zoned.h"
  
  /* magic values for the inode_only field in btrfs_log_inode:
   *
   * LOG_INODE_ALL means to log everything
   * LOG_INODE_EXISTS means to log just enough to recreate the inode
   * during log replay
   */
  enum {
  	LOG_INODE_ALL,
  	LOG_INODE_EXISTS,
  	LOG_OTHER_INODE,
  	LOG_OTHER_INODE_ALL,
  };
  
  /*
   * directory trouble cases
   *
   * 1) on rename or unlink, if the inode being unlinked isn't in the fsync
   * log, we must force a full commit before doing an fsync of the directory
   * where the unlink was done.
   * ---> record transid of last unlink/rename per directory
   *
   * mkdir foo/some_dir
   * normal commit
   * rename foo/some_dir foo2/some_dir
   * mkdir foo/some_dir
   * fsync foo/some_dir/some_file
   *
   * The fsync above will unlink the original some_dir without recording
   * it in its new location (foo2).  After a crash, some_dir will be gone
   * unless the fsync of some_file forces a full commit
   *
   * 2) we must log any new names for any file or dir that is in the fsync
   * log. ---> check inode while renaming/linking.
   *
   * 2a) we must log any new names for any file or dir during rename
   * when the directory they are being removed from was logged.
   * ---> check inode and old parent dir during rename
   *
   *  2a is actually the more important variant.  With the extra logging
   *  a crash might unlink the old name without recreating the new one
   *
   * 3) after a crash, we must go through any directories with a link count
   * of zero and redo the rm -rf
   *
   * mkdir f1/foo
   * normal commit
   * rm -rf f1/foo
   * fsync(f1)
   *
   * The directory f1 was fully removed from the FS, but fsync was never
   * called on f1, only its parent dir.  After a crash the rm -rf must
   * be replayed.  This must be able to recurse down the entire
   * directory tree.  The inode link count fixup code takes care of the
   * ugly details.
   */
  
  /*
   * stages for the tree walking.  The first
   * stage (0) is to only pin down the blocks we find
   * the second stage (1) is to make sure that all the inodes
   * we find in the log are created in the subvolume.
   *
   * The last stage is to deal with directories and links and extents
   * and all the other fun semantics
   */
  enum {
  	LOG_WALK_PIN_ONLY,
  	LOG_WALK_REPLAY_INODES,
  	LOG_WALK_REPLAY_DIR_INDEX,
  	LOG_WALK_REPLAY_ALL,
  };
  
  static int btrfs_log_inode(struct btrfs_trans_handle *trans,
  			   struct btrfs_root *root, struct btrfs_inode *inode,
  			   int inode_only,
  			   struct btrfs_log_ctx *ctx);
  static int link_to_fixup_dir(struct btrfs_trans_handle *trans,
  			     struct btrfs_root *root,
  			     struct btrfs_path *path, u64 objectid);
  static noinline int replay_dir_deletes(struct btrfs_trans_handle *trans,
  				       struct btrfs_root *root,
  				       struct btrfs_root *log,
  				       struct btrfs_path *path,
  				       u64 dirid, int del_all);
  static void wait_log_commit(struct btrfs_root *root, int transid);
  
  /*
   * tree logging is a special write ahead log used to make sure that
   * fsyncs and O_SYNCs can happen without doing full tree commits.
   *
   * Full tree commits are expensive because they require commonly
   * modified blocks to be recowed, creating many dirty pages in the
   * extent tree an 4x-6x higher write load than ext3.
   *
   * Instead of doing a tree commit on every fsync, we use the
   * key ranges and transaction ids to find items for a given file or directory
   * that have changed in this transaction.  Those items are copied into
   * a special tree (one per subvolume root), that tree is written to disk
   * and then the fsync is considered complete.
   *
   * After a crash, items are copied out of the log-tree back into the
   * subvolume tree.  Any file data extents found are recorded in the extent
   * allocation tree, and the log-tree freed.
   *
   * The log tree is read three times, once to pin down all the extents it is
   * using in ram and once, once to create all the inodes logged in the tree
   * and once to do all the other items.
   */
  
  /*
   * start a sub transaction and setup the log tree
   * this increments the log tree writer count to make the people
   * syncing the tree wait for us to finish
   */
  static int start_log_trans(struct btrfs_trans_handle *trans,
  			   struct btrfs_root *root,
  			   struct btrfs_log_ctx *ctx)
  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	struct btrfs_root *tree_root = fs_info->tree_root;
  	const bool zoned = btrfs_is_zoned(fs_info);
  	int ret = 0;
  	bool created = false;
  
  	/*
  	 * First check if the log root tree was already created. If not, create
  	 * it before locking the root's log_mutex, just to keep lockdep happy.
  	 */
  	if (!test_bit(BTRFS_ROOT_HAS_LOG_TREE, &tree_root->state)) {
  		mutex_lock(&tree_root->log_mutex);
  		if (!fs_info->log_root_tree) {
  			ret = btrfs_init_log_root_tree(trans, fs_info);
  			if (!ret) {
  				set_bit(BTRFS_ROOT_HAS_LOG_TREE, &tree_root->state);
  				created = true;
  			}
  		}
  		mutex_unlock(&tree_root->log_mutex);
  		if (ret)
  			return ret;
  	}
  
  	mutex_lock(&root->log_mutex);
  
  again:
  	if (root->log_root) {
  		int index = (root->log_transid + 1) % 2;
  
  		if (btrfs_need_log_full_commit(trans)) {
  			ret = -EAGAIN;
  			goto out;
  		}
  
  		if (zoned && atomic_read(&root->log_commit[index])) {
  			wait_log_commit(root, root->log_transid - 1);
  			goto again;
  		}
  
  		if (!root->log_start_pid) {
  			clear_bit(BTRFS_ROOT_MULTI_LOG_TASKS, &root->state);
  			root->log_start_pid = current->pid;
  		} else if (root->log_start_pid != current->pid) {
  			set_bit(BTRFS_ROOT_MULTI_LOG_TASKS, &root->state);
  		}
  	} else {
  		/*
  		 * This means fs_info->log_root_tree was already created
  		 * for some other FS trees. Do the full commit not to mix
  		 * nodes from multiple log transactions to do sequential
  		 * writing.
  		 */
  		if (zoned && !created) {
  			ret = -EAGAIN;
  			goto out;
  		}
  
  		ret = btrfs_add_log_tree(trans, root);
  		if (ret)
  			goto out;
  
  		set_bit(BTRFS_ROOT_HAS_LOG_TREE, &root->state);
  		clear_bit(BTRFS_ROOT_MULTI_LOG_TASKS, &root->state);
  		root->log_start_pid = current->pid;
  	}
  
  	atomic_inc(&root->log_writers);
  	if (ctx && !ctx->logging_new_name) {
  		int index = root->log_transid % 2;
  		list_add_tail(&ctx->list, &root->log_ctxs[index]);
  		ctx->log_transid = root->log_transid;
  	}
  
  out:
  	mutex_unlock(&root->log_mutex);
  	return ret;
  }
  
  /*
   * returns 0 if there was a log transaction running and we were able
   * to join, or returns -ENOENT if there were not transactions
   * in progress
   */
  static int join_running_log_trans(struct btrfs_root *root)
  {
  	const bool zoned = btrfs_is_zoned(root->fs_info);
  	int ret = -ENOENT;
  
  	if (!test_bit(BTRFS_ROOT_HAS_LOG_TREE, &root->state))
  		return ret;
  
  	mutex_lock(&root->log_mutex);
  again:
  	if (root->log_root) {
  		int index = (root->log_transid + 1) % 2;
  
  		ret = 0;
  		if (zoned && atomic_read(&root->log_commit[index])) {
  			wait_log_commit(root, root->log_transid - 1);
  			goto again;
  		}
  		atomic_inc(&root->log_writers);
  	}
  	mutex_unlock(&root->log_mutex);
  	return ret;
  }
  
  /*
   * This either makes the current running log transaction wait
   * until you call btrfs_end_log_trans() or it makes any future
   * log transactions wait until you call btrfs_end_log_trans()
   */
  void btrfs_pin_log_trans(struct btrfs_root *root)
  {
  	atomic_inc(&root->log_writers);
  }
  
  /*
   * indicate we're done making changes to the log tree
   * and wake up anyone waiting to do a sync
   */
  void btrfs_end_log_trans(struct btrfs_root *root)
  {
  	if (atomic_dec_and_test(&root->log_writers)) {
  		/* atomic_dec_and_test implies a barrier */
  		cond_wake_up_nomb(&root->log_writer_wait);
  	}
  }
  
  static int btrfs_write_tree_block(struct extent_buffer *buf)
  {
  	return filemap_fdatawrite_range(buf->pages[0]->mapping, buf->start,
  					buf->start + buf->len - 1);
  }
  
  static void btrfs_wait_tree_block_writeback(struct extent_buffer *buf)
  {
  	filemap_fdatawait_range(buf->pages[0]->mapping,
  			        buf->start, buf->start + buf->len - 1);
  }
  
  /*
   * the walk control struct is used to pass state down the chain when
   * processing the log tree.  The stage field tells us which part
   * of the log tree processing we are currently doing.  The others
   * are state fields used for that specific part
   */
  struct walk_control {
  	/* should we free the extent on disk when done?  This is used
  	 * at transaction commit time while freeing a log tree
  	 */
  	int free;
  
  	/* should we write out the extent buffer?  This is used
  	 * while flushing the log tree to disk during a sync
  	 */
  	int write;
  
  	/* should we wait for the extent buffer io to finish?  Also used
  	 * while flushing the log tree to disk for a sync
  	 */
  	int wait;
  
  	/* pin only walk, we record which extents on disk belong to the
  	 * log trees
  	 */
  	int pin;
  
  	/* what stage of the replay code we're currently in */
  	int stage;
  
  	/*
  	 * Ignore any items from the inode currently being processed. Needs
  	 * to be set every time we find a BTRFS_INODE_ITEM_KEY and we are in
  	 * the LOG_WALK_REPLAY_INODES stage.
  	 */
  	bool ignore_cur_inode;
  
  	/* the root we are currently replaying */
  	struct btrfs_root *replay_dest;
  
  	/* the trans handle for the current replay */
  	struct btrfs_trans_handle *trans;
  
  	/* the function that gets used to process blocks we find in the
  	 * tree.  Note the extent_buffer might not be up to date when it is
  	 * passed in, and it must be checked or read if you need the data
  	 * inside it
  	 */
  	int (*process_func)(struct btrfs_root *log, struct extent_buffer *eb,
  			    struct walk_control *wc, u64 gen, int level);
  };
  
  /*
   * process_func used to pin down extents, write them or wait on them
   */
  static int process_one_buffer(struct btrfs_root *log,
  			      struct extent_buffer *eb,
  			      struct walk_control *wc, u64 gen, int level)
  {
  	struct btrfs_fs_info *fs_info = log->fs_info;
  	int ret = 0;
  
  	/*
  	 * If this fs is mixed then we need to be able to process the leaves to
  	 * pin down any logged extents, so we have to read the block.
  	 */
  	if (btrfs_fs_incompat(fs_info, MIXED_GROUPS)) {
  		ret = btrfs_read_buffer(eb, gen, level, NULL);
  		if (ret)
  			return ret;
  	}
  
  	if (wc->pin)
  		ret = btrfs_pin_extent_for_log_replay(wc->trans, eb->start,
  						      eb->len);
  
  	if (!ret && btrfs_buffer_uptodate(eb, gen, 0)) {
  		if (wc->pin && btrfs_header_level(eb) == 0)
  			ret = btrfs_exclude_logged_extents(eb);
  		if (wc->write)
  			btrfs_write_tree_block(eb);
  		if (wc->wait)
  			btrfs_wait_tree_block_writeback(eb);
  	}
  	return ret;
  }
  
  /*
   * Item overwrite used by replay and tree logging.  eb, slot and key all refer
   * to the src data we are copying out.
   *
   * root is the tree we are copying into, and path is a scratch
   * path for use in this function (it should be released on entry and
   * will be released on exit).
   *
   * If the key is already in the destination tree the existing item is
   * overwritten.  If the existing item isn't big enough, it is extended.
   * If it is too large, it is truncated.
   *
   * If the key isn't in the destination yet, a new item is inserted.
   */
  static noinline int overwrite_item(struct btrfs_trans_handle *trans,
  				   struct btrfs_root *root,
  				   struct btrfs_path *path,
  				   struct extent_buffer *eb, int slot,
  				   struct btrfs_key *key)
  {
  	int ret;
  	u32 item_size;
  	u64 saved_i_size = 0;
  	int save_old_i_size = 0;
  	unsigned long src_ptr;
  	unsigned long dst_ptr;
  	int overwrite_root = 0;
  	bool inode_item = key->type == BTRFS_INODE_ITEM_KEY;
  
  	if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)
  		overwrite_root = 1;
  
  	item_size = btrfs_item_size_nr(eb, slot);
  	src_ptr = btrfs_item_ptr_offset(eb, slot);
  
  	/* look for the key in the destination tree */
  	ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
  	if (ret < 0)
  		return ret;
  
  	if (ret == 0) {
  		char *src_copy;
  		char *dst_copy;
  		u32 dst_size = btrfs_item_size_nr(path->nodes[0],
  						  path->slots[0]);
  		if (dst_size != item_size)
  			goto insert;
  
  		if (item_size == 0) {
  			btrfs_release_path(path);
  			return 0;
  		}
  		dst_copy = kmalloc(item_size, GFP_NOFS);
  		src_copy = kmalloc(item_size, GFP_NOFS);
  		if (!dst_copy || !src_copy) {
  			btrfs_release_path(path);
  			kfree(dst_copy);
  			kfree(src_copy);
  			return -ENOMEM;
  		}
  
  		read_extent_buffer(eb, src_copy, src_ptr, item_size);
  
  		dst_ptr = btrfs_item_ptr_offset(path->nodes[0], path->slots[0]);
  		read_extent_buffer(path->nodes[0], dst_copy, dst_ptr,
  				   item_size);
  		ret = memcmp(dst_copy, src_copy, item_size);
  
  		kfree(dst_copy);
  		kfree(src_copy);
  		/*
  		 * they have the same contents, just return, this saves
  		 * us from cowing blocks in the destination tree and doing
  		 * extra writes that may not have been done by a previous
  		 * sync
  		 */
  		if (ret == 0) {
  			btrfs_release_path(path);
  			return 0;
  		}
  
  		/*
  		 * We need to load the old nbytes into the inode so when we
  		 * replay the extents we've logged we get the right nbytes.
  		 */
  		if (inode_item) {
  			struct btrfs_inode_item *item;
  			u64 nbytes;
  			u32 mode;
  
  			item = btrfs_item_ptr(path->nodes[0], path->slots[0],
  					      struct btrfs_inode_item);
  			nbytes = btrfs_inode_nbytes(path->nodes[0], item);
  			item = btrfs_item_ptr(eb, slot,
  					      struct btrfs_inode_item);
  			btrfs_set_inode_nbytes(eb, item, nbytes);
  
  			/*
  			 * If this is a directory we need to reset the i_size to
  			 * 0 so that we can set it up properly when replaying
  			 * the rest of the items in this log.
  			 */
  			mode = btrfs_inode_mode(eb, item);
  			if (S_ISDIR(mode))
  				btrfs_set_inode_size(eb, item, 0);
  		}
  	} else if (inode_item) {
  		struct btrfs_inode_item *item;
  		u32 mode;
  
  		/*
  		 * New inode, set nbytes to 0 so that the nbytes comes out
  		 * properly when we replay the extents.
  		 */
  		item = btrfs_item_ptr(eb, slot, struct btrfs_inode_item);
  		btrfs_set_inode_nbytes(eb, item, 0);
  
  		/*
  		 * If this is a directory we need to reset the i_size to 0 so
  		 * that we can set it up properly when replaying the rest of
  		 * the items in this log.
  		 */
  		mode = btrfs_inode_mode(eb, item);
  		if (S_ISDIR(mode))
  			btrfs_set_inode_size(eb, item, 0);
  	}
  insert:
  	btrfs_release_path(path);
  	/* try to insert the key into the destination tree */
  	path->skip_release_on_error = 1;
  	ret = btrfs_insert_empty_item(trans, root, path,
  				      key, item_size);
  	path->skip_release_on_error = 0;
  
  	/* make sure any existing item is the correct size */
  	if (ret == -EEXIST || ret == -EOVERFLOW) {
  		u32 found_size;
  		found_size = btrfs_item_size_nr(path->nodes[0],
  						path->slots[0]);
  		if (found_size > item_size)
  			btrfs_truncate_item(path, item_size, 1);
  		else if (found_size < item_size)
  			btrfs_extend_item(path, item_size - found_size);
  	} else if (ret) {
  		return ret;
  	}
  	dst_ptr = btrfs_item_ptr_offset(path->nodes[0],
  					path->slots[0]);
  
  	/* don't overwrite an existing inode if the generation number
  	 * was logged as zero.  This is done when the tree logging code
  	 * is just logging an inode to make sure it exists after recovery.
  	 *
  	 * Also, don't overwrite i_size on directories during replay.
  	 * log replay inserts and removes directory items based on the
  	 * state of the tree found in the subvolume, and i_size is modified
  	 * as it goes
  	 */
  	if (key->type == BTRFS_INODE_ITEM_KEY && ret == -EEXIST) {
  		struct btrfs_inode_item *src_item;
  		struct btrfs_inode_item *dst_item;
  
  		src_item = (struct btrfs_inode_item *)src_ptr;
  		dst_item = (struct btrfs_inode_item *)dst_ptr;
  
  		if (btrfs_inode_generation(eb, src_item) == 0) {
  			struct extent_buffer *dst_eb = path->nodes[0];
  			const u64 ino_size = btrfs_inode_size(eb, src_item);
  
  			/*
  			 * For regular files an ino_size == 0 is used only when
  			 * logging that an inode exists, as part of a directory
  			 * fsync, and the inode wasn't fsynced before. In this
  			 * case don't set the size of the inode in the fs/subvol
  			 * tree, otherwise we would be throwing valid data away.
  			 */
  			if (S_ISREG(btrfs_inode_mode(eb, src_item)) &&
  			    S_ISREG(btrfs_inode_mode(dst_eb, dst_item)) &&
  			    ino_size != 0)
  				btrfs_set_inode_size(dst_eb, dst_item, ino_size);
  			goto no_copy;
  		}
  
  		if (overwrite_root &&
  		    S_ISDIR(btrfs_inode_mode(eb, src_item)) &&
  		    S_ISDIR(btrfs_inode_mode(path->nodes[0], dst_item))) {
  			save_old_i_size = 1;
  			saved_i_size = btrfs_inode_size(path->nodes[0],
  							dst_item);
  		}
  	}
  
  	copy_extent_buffer(path->nodes[0], eb, dst_ptr,
  			   src_ptr, item_size);
  
  	if (save_old_i_size) {
  		struct btrfs_inode_item *dst_item;
  		dst_item = (struct btrfs_inode_item *)dst_ptr;
  		btrfs_set_inode_size(path->nodes[0], dst_item, saved_i_size);
  	}
  
  	/* make sure the generation is filled in */
  	if (key->type == BTRFS_INODE_ITEM_KEY) {
  		struct btrfs_inode_item *dst_item;
  		dst_item = (struct btrfs_inode_item *)dst_ptr;
  		if (btrfs_inode_generation(path->nodes[0], dst_item) == 0) {
  			btrfs_set_inode_generation(path->nodes[0], dst_item,
  						   trans->transid);
  		}
  	}
  no_copy:
  	btrfs_mark_buffer_dirty(path->nodes[0]);
  	btrfs_release_path(path);
  	return 0;
  }
  
  /*
   * simple helper to read an inode off the disk from a given root
   * This can only be called for subvolume roots and not for the log
   */
  static noinline struct inode *read_one_inode(struct btrfs_root *root,
  					     u64 objectid)
  {
  	struct inode *inode;
  
  	inode = btrfs_iget(root->fs_info->sb, objectid, root);
  	if (IS_ERR(inode))
  		inode = NULL;
  	return inode;
  }
  
  /* replays a single extent in 'eb' at 'slot' with 'key' into the
   * subvolume 'root'.  path is released on entry and should be released
   * on exit.
   *
   * extents in the log tree have not been allocated out of the extent
   * tree yet.  So, this completes the allocation, taking a reference
   * as required if the extent already exists or creating a new extent
   * if it isn't in the extent allocation tree yet.
   *
   * The extent is inserted into the file, dropping any existing extents
   * from the file that overlap the new one.
   */
  static noinline int replay_one_extent(struct btrfs_trans_handle *trans,
  				      struct btrfs_root *root,
  				      struct btrfs_path *path,
  				      struct extent_buffer *eb, int slot,
  				      struct btrfs_key *key)
  {
  	struct btrfs_drop_extents_args drop_args = { 0 };
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	int found_type;
  	u64 extent_end;
  	u64 start = key->offset;
  	u64 nbytes = 0;
  	struct btrfs_file_extent_item *item;
  	struct inode *inode = NULL;
  	unsigned long size;
  	int ret = 0;
  
  	item = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
  	found_type = btrfs_file_extent_type(eb, item);
  
  	if (found_type == BTRFS_FILE_EXTENT_REG ||
  	    found_type == BTRFS_FILE_EXTENT_PREALLOC) {
  		nbytes = btrfs_file_extent_num_bytes(eb, item);
  		extent_end = start + nbytes;
  
  		/*
  		 * We don't add to the inodes nbytes if we are prealloc or a
  		 * hole.
  		 */
  		if (btrfs_file_extent_disk_bytenr(eb, item) == 0)
  			nbytes = 0;
  	} else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
  		size = btrfs_file_extent_ram_bytes(eb, item);
  		nbytes = btrfs_file_extent_ram_bytes(eb, item);
  		extent_end = ALIGN(start + size,
  				   fs_info->sectorsize);
  	} else {
  		ret = 0;
  		goto out;
  	}
  
  	inode = read_one_inode(root, key->objectid);
  	if (!inode) {
  		ret = -EIO;
  		goto out;
  	}
  
  	/*
  	 * first check to see if we already have this extent in the
  	 * file.  This must be done before the btrfs_drop_extents run
  	 * so we don't try to drop this extent.
  	 */
  	ret = btrfs_lookup_file_extent(trans, root, path,
  			btrfs_ino(BTRFS_I(inode)), start, 0);
  
  	if (ret == 0 &&
  	    (found_type == BTRFS_FILE_EXTENT_REG ||
  	     found_type == BTRFS_FILE_EXTENT_PREALLOC)) {
  		struct btrfs_file_extent_item cmp1;
  		struct btrfs_file_extent_item cmp2;
  		struct btrfs_file_extent_item *existing;
  		struct extent_buffer *leaf;
  
  		leaf = path->nodes[0];
  		existing = btrfs_item_ptr(leaf, path->slots[0],
  					  struct btrfs_file_extent_item);
  
  		read_extent_buffer(eb, &cmp1, (unsigned long)item,
  				   sizeof(cmp1));
  		read_extent_buffer(leaf, &cmp2, (unsigned long)existing,
  				   sizeof(cmp2));
  
  		/*
  		 * we already have a pointer to this exact extent,
  		 * we don't have to do anything
  		 */
  		if (memcmp(&cmp1, &cmp2, sizeof(cmp1)) == 0) {
  			btrfs_release_path(path);
  			goto out;
  		}
  	}
  	btrfs_release_path(path);
  
  	/* drop any overlapping extents */
  	drop_args.start = start;
  	drop_args.end = extent_end;
  	drop_args.drop_cache = true;
  	ret = btrfs_drop_extents(trans, root, BTRFS_I(inode), &drop_args);
  	if (ret)
  		goto out;
  
  	if (found_type == BTRFS_FILE_EXTENT_REG ||
  	    found_type == BTRFS_FILE_EXTENT_PREALLOC) {
  		u64 offset;
  		unsigned long dest_offset;
  		struct btrfs_key ins;
  
  		if (btrfs_file_extent_disk_bytenr(eb, item) == 0 &&
  		    btrfs_fs_incompat(fs_info, NO_HOLES))
  			goto update_inode;
  
  		ret = btrfs_insert_empty_item(trans, root, path, key,
  					      sizeof(*item));
  		if (ret)
  			goto out;
  		dest_offset = btrfs_item_ptr_offset(path->nodes[0],
  						    path->slots[0]);
  		copy_extent_buffer(path->nodes[0], eb, dest_offset,
  				(unsigned long)item,  sizeof(*item));
  
  		ins.objectid = btrfs_file_extent_disk_bytenr(eb, item);
  		ins.offset = btrfs_file_extent_disk_num_bytes(eb, item);
  		ins.type = BTRFS_EXTENT_ITEM_KEY;
  		offset = key->offset - btrfs_file_extent_offset(eb, item);
  
  		/*
  		 * Manually record dirty extent, as here we did a shallow
  		 * file extent item copy and skip normal backref update,
  		 * but modifying extent tree all by ourselves.
  		 * So need to manually record dirty extent for qgroup,
  		 * as the owner of the file extent changed from log tree
  		 * (doesn't affect qgroup) to fs/file tree(affects qgroup)
  		 */
  		ret = btrfs_qgroup_trace_extent(trans,
  				btrfs_file_extent_disk_bytenr(eb, item),
  				btrfs_file_extent_disk_num_bytes(eb, item),
  				GFP_NOFS);
  		if (ret < 0)
  			goto out;
  
  		if (ins.objectid > 0) {
  			struct btrfs_ref ref = { 0 };
  			u64 csum_start;
  			u64 csum_end;
  			LIST_HEAD(ordered_sums);
  
  			/*
  			 * is this extent already allocated in the extent
  			 * allocation tree?  If so, just add a reference
  			 */
  			ret = btrfs_lookup_data_extent(fs_info, ins.objectid,
  						ins.offset);
  			if (ret < 0) {
  				goto out;
  			} else if (ret == 0) {
  				btrfs_init_generic_ref(&ref,
  						BTRFS_ADD_DELAYED_REF,
  						ins.objectid, ins.offset, 0);
  				btrfs_init_data_ref(&ref,
  						root->root_key.objectid,
  						key->objectid, offset);
  				ret = btrfs_inc_extent_ref(trans, &ref);
  				if (ret)
  					goto out;
  			} else {
  				/*
  				 * insert the extent pointer in the extent
  				 * allocation tree
  				 */
  				ret = btrfs_alloc_logged_file_extent(trans,
  						root->root_key.objectid,
  						key->objectid, offset, &ins);
  				if (ret)
  					goto out;
  			}
  			btrfs_release_path(path);
  
  			if (btrfs_file_extent_compression(eb, item)) {
  				csum_start = ins.objectid;
  				csum_end = csum_start + ins.offset;
  			} else {
  				csum_start = ins.objectid +
  					btrfs_file_extent_offset(eb, item);
  				csum_end = csum_start +
  					btrfs_file_extent_num_bytes(eb, item);
  			}
  
  			ret = btrfs_lookup_csums_range(root->log_root,
  						csum_start, csum_end - 1,
  						&ordered_sums, 0);
  			if (ret)
  				goto out;
  			/*
  			 * Now delete all existing cums in the csum root that
  			 * cover our range. We do this because we can have an
  			 * extent that is completely referenced by one file
  			 * extent item and partially referenced by another
  			 * file extent item (like after using the clone or
  			 * extent_same ioctls). In this case if we end up doing
  			 * the replay of the one that partially references the
  			 * extent first, and we do not do the csum deletion
  			 * below, we can get 2 csum items in the csum tree that
  			 * overlap each other. For example, imagine our log has
  			 * the two following file extent items:
  			 *
  			 * key (257 EXTENT_DATA 409600)
  			 *     extent data disk byte 12845056 nr 102400
  			 *     extent data offset 20480 nr 20480 ram 102400
  			 *
  			 * key (257 EXTENT_DATA 819200)
  			 *     extent data disk byte 12845056 nr 102400
  			 *     extent data offset 0 nr 102400 ram 102400
  			 *
  			 * Where the second one fully references the 100K extent
  			 * that starts at disk byte 12845056, and the log tree
  			 * has a single csum item that covers the entire range
  			 * of the extent:
  			 *
  			 * key (EXTENT_CSUM EXTENT_CSUM 12845056) itemsize 100
  			 *
  			 * After the first file extent item is replayed, the
  			 * csum tree gets the following csum item:
  			 *
  			 * key (EXTENT_CSUM EXTENT_CSUM 12865536) itemsize 20
  			 *
  			 * Which covers the 20K sub-range starting at offset 20K
  			 * of our extent. Now when we replay the second file
  			 * extent item, if we do not delete existing csum items
  			 * that cover any of its blocks, we end up getting two
  			 * csum items in our csum tree that overlap each other:
  			 *
  			 * key (EXTENT_CSUM EXTENT_CSUM 12845056) itemsize 100
  			 * key (EXTENT_CSUM EXTENT_CSUM 12865536) itemsize 20
  			 *
  			 * Which is a problem, because after this anyone trying
  			 * to lookup up for the checksum of any block of our
  			 * extent starting at an offset of 40K or higher, will
  			 * end up looking at the second csum item only, which
  			 * does not contain the checksum for any block starting
  			 * at offset 40K or higher of our extent.
  			 */
  			while (!list_empty(&ordered_sums)) {
  				struct btrfs_ordered_sum *sums;
  				sums = list_entry(ordered_sums.next,
  						struct btrfs_ordered_sum,
  						list);
  				if (!ret)
  					ret = btrfs_del_csums(trans,
  							      fs_info->csum_root,
  							      sums->bytenr,
  							      sums->len);
  				if (!ret)
  					ret = btrfs_csum_file_blocks(trans,
  						fs_info->csum_root, sums);
  				list_del(&sums->list);
  				kfree(sums);
  			}
  			if (ret)
  				goto out;
  		} else {
  			btrfs_release_path(path);
  		}
  	} else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
  		/* inline extents are easy, we just overwrite them */
  		ret = overwrite_item(trans, root, path, eb, slot, key);
  		if (ret)
  			goto out;
  	}
  
  	ret = btrfs_inode_set_file_extent_range(BTRFS_I(inode), start,
  						extent_end - start);
  	if (ret)
  		goto out;
  
  update_inode:
  	btrfs_update_inode_bytes(BTRFS_I(inode), nbytes, drop_args.bytes_found);
  	ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
  out:
  	if (inode)
  		iput(inode);
  	return ret;
  }
  
  /*
   * when cleaning up conflicts between the directory names in the
   * subvolume, directory names in the log and directory names in the
   * inode back references, we may have to unlink inodes from directories.
   *
   * This is a helper function to do the unlink of a specific directory
   * item
   */
  static noinline int drop_one_dir_item(struct btrfs_trans_handle *trans,
  				      struct btrfs_root *root,
  				      struct btrfs_path *path,
  				      struct btrfs_inode *dir,
  				      struct btrfs_dir_item *di)
  {
  	struct inode *inode;
  	char *name;
  	int name_len;
  	struct extent_buffer *leaf;
  	struct btrfs_key location;
  	int ret;
  
  	leaf = path->nodes[0];
  
  	btrfs_dir_item_key_to_cpu(leaf, di, &location);
  	name_len = btrfs_dir_name_len(leaf, di);
  	name = kmalloc(name_len, GFP_NOFS);
  	if (!name)
  		return -ENOMEM;
  
  	read_extent_buffer(leaf, name, (unsigned long)(di + 1), name_len);
  	btrfs_release_path(path);
  
  	inode = read_one_inode(root, location.objectid);
  	if (!inode) {
  		ret = -EIO;
  		goto out;
  	}
  
  	ret = link_to_fixup_dir(trans, root, path, location.objectid);
  	if (ret)
  		goto out;
  
  	ret = btrfs_unlink_inode(trans, root, dir, BTRFS_I(inode), name,
  			name_len);
  	if (ret)
  		goto out;
  	else
  		ret = btrfs_run_delayed_items(trans);
  out:
  	kfree(name);
  	iput(inode);
  	return ret;
  }
  
  /*
   * See if a given name and sequence number found in an inode back reference are
   * already in a directory and correctly point to this inode.
   *
   * Returns: < 0 on error, 0 if the directory entry does not exists and 1 if it
   * exists.
   */
  static noinline int inode_in_dir(struct btrfs_root *root,
  				 struct btrfs_path *path,
  				 u64 dirid, u64 objectid, u64 index,
  				 const char *name, int name_len)
  {
  	struct btrfs_dir_item *di;
  	struct btrfs_key location;
  	int ret = 0;
  
  	di = btrfs_lookup_dir_index_item(NULL, root, path, dirid,
  					 index, name, name_len, 0);
  	if (IS_ERR(di)) {
  		ret = PTR_ERR(di);
  		goto out;
  	} else if (di) {
  		btrfs_dir_item_key_to_cpu(path->nodes[0], di, &location);
  		if (location.objectid != objectid)
  			goto out;
  	} else {
  		goto out;
  	}
  
  	btrfs_release_path(path);
  	di = btrfs_lookup_dir_item(NULL, root, path, dirid, name, name_len, 0);
  	if (IS_ERR(di)) {
  		ret = PTR_ERR(di);
  		goto out;
  	} else if (di) {
  		btrfs_dir_item_key_to_cpu(path->nodes[0], di, &location);
  		if (location.objectid == objectid)
  			ret = 1;
  	}
  out:
  	btrfs_release_path(path);
  	return ret;
  }
  
  /*
   * helper function to check a log tree for a named back reference in
   * an inode.  This is used to decide if a back reference that is
   * found in the subvolume conflicts with what we find in the log.
   *
   * inode backreferences may have multiple refs in a single item,
   * during replay we process one reference at a time, and we don't
   * want to delete valid links to a file from the subvolume if that
   * link is also in the log.
   */
  static noinline int backref_in_log(struct btrfs_root *log,
  				   struct btrfs_key *key,
  				   u64 ref_objectid,
  				   const char *name, int namelen)
  {
  	struct btrfs_path *path;
  	int ret;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	ret = btrfs_search_slot(NULL, log, key, path, 0, 0);
  	if (ret < 0) {
  		goto out;
  	} else if (ret == 1) {
  		ret = 0;
  		goto out;
  	}
  
  	if (key->type == BTRFS_INODE_EXTREF_KEY)
  		ret = !!btrfs_find_name_in_ext_backref(path->nodes[0],
  						       path->slots[0],
  						       ref_objectid,
  						       name, namelen);
  	else
  		ret = !!btrfs_find_name_in_backref(path->nodes[0],
  						   path->slots[0],
  						   name, namelen);
  out:
  	btrfs_free_path(path);
  	return ret;
  }
  
  static inline int __add_inode_ref(struct btrfs_trans_handle *trans,
  				  struct btrfs_root *root,
  				  struct btrfs_path *path,
  				  struct btrfs_root *log_root,
  				  struct btrfs_inode *dir,
  				  struct btrfs_inode *inode,
  				  u64 inode_objectid, u64 parent_objectid,
  				  u64 ref_index, char *name, int namelen,
  				  int *search_done)
  {
  	int ret;
  	char *victim_name;
  	int victim_name_len;
  	struct extent_buffer *leaf;
  	struct btrfs_dir_item *di;
  	struct btrfs_key search_key;
  	struct btrfs_inode_extref *extref;
  
  again:
  	/* Search old style refs */
  	search_key.objectid = inode_objectid;
  	search_key.type = BTRFS_INODE_REF_KEY;
  	search_key.offset = parent_objectid;
  	ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
  	if (ret == 0) {
  		struct btrfs_inode_ref *victim_ref;
  		unsigned long ptr;
  		unsigned long ptr_end;
  
  		leaf = path->nodes[0];
  
  		/* are we trying to overwrite a back ref for the root directory
  		 * if so, just jump out, we're done
  		 */
  		if (search_key.objectid == search_key.offset)
  			return 1;
  
  		/* check all the names in this back reference to see
  		 * if they are in the log.  if so, we allow them to stay
  		 * otherwise they must be unlinked as a conflict
  		 */
  		ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
  		ptr_end = ptr + btrfs_item_size_nr(leaf, path->slots[0]);
  		while (ptr < ptr_end) {
  			victim_ref = (struct btrfs_inode_ref *)ptr;
  			victim_name_len = btrfs_inode_ref_name_len(leaf,
  								   victim_ref);
  			victim_name = kmalloc(victim_name_len, GFP_NOFS);
  			if (!victim_name)
  				return -ENOMEM;
  
  			read_extent_buffer(leaf, victim_name,
  					   (unsigned long)(victim_ref + 1),
  					   victim_name_len);
  
  			ret = backref_in_log(log_root, &search_key,
  					     parent_objectid, victim_name,
  					     victim_name_len);
  			if (ret < 0) {
  				kfree(victim_name);
  				return ret;
  			} else if (!ret) {
  				inc_nlink(&inode->vfs_inode);
  				btrfs_release_path(path);
  
  				ret = btrfs_unlink_inode(trans, root, dir, inode,
  						victim_name, victim_name_len);
  				kfree(victim_name);
  				if (ret)
  					return ret;
  				ret = btrfs_run_delayed_items(trans);
  				if (ret)
  					return ret;
  				*search_done = 1;
  				goto again;
  			}
  			kfree(victim_name);
  
  			ptr = (unsigned long)(victim_ref + 1) + victim_name_len;
  		}
  
  		/*
  		 * NOTE: we have searched root tree and checked the
  		 * corresponding ref, it does not need to check again.
  		 */
  		*search_done = 1;
  	}
  	btrfs_release_path(path);
  
  	/* Same search but for extended refs */
  	extref = btrfs_lookup_inode_extref(NULL, root, path, name, namelen,
  					   inode_objectid, parent_objectid, 0,
  					   0);
  	if (!IS_ERR_OR_NULL(extref)) {
  		u32 item_size;
  		u32 cur_offset = 0;
  		unsigned long base;
  		struct inode *victim_parent;
  
  		leaf = path->nodes[0];
  
  		item_size = btrfs_item_size_nr(leaf, path->slots[0]);
  		base = btrfs_item_ptr_offset(leaf, path->slots[0]);
  
  		while (cur_offset < item_size) {
  			extref = (struct btrfs_inode_extref *)(base + cur_offset);
  
  			victim_name_len = btrfs_inode_extref_name_len(leaf, extref);
  
  			if (btrfs_inode_extref_parent(leaf, extref) != parent_objectid)
  				goto next;
  
  			victim_name = kmalloc(victim_name_len, GFP_NOFS);
  			if (!victim_name)
  				return -ENOMEM;
  			read_extent_buffer(leaf, victim_name, (unsigned long)&extref->name,
  					   victim_name_len);
  
  			search_key.objectid = inode_objectid;
  			search_key.type = BTRFS_INODE_EXTREF_KEY;
  			search_key.offset = btrfs_extref_hash(parent_objectid,
  							      victim_name,
  							      victim_name_len);
  			ret = backref_in_log(log_root, &search_key,
  					     parent_objectid, victim_name,
  					     victim_name_len);
  			if (ret < 0) {
  				kfree(victim_name);
  				return ret;
  			} else if (!ret) {
  				ret = -ENOENT;
  				victim_parent = read_one_inode(root,
  						parent_objectid);
  				if (victim_parent) {
  					inc_nlink(&inode->vfs_inode);
  					btrfs_release_path(path);
  
  					ret = btrfs_unlink_inode(trans, root,
  							BTRFS_I(victim_parent),
  							inode,
  							victim_name,
  							victim_name_len);
  					if (!ret)
  						ret = btrfs_run_delayed_items(
  								  trans);
  				}
  				iput(victim_parent);
  				kfree(victim_name);
  				if (ret)
  					return ret;
  				*search_done = 1;
  				goto again;
  			}
  			kfree(victim_name);
  next:
  			cur_offset += victim_name_len + sizeof(*extref);
  		}
  		*search_done = 1;
  	}
  	btrfs_release_path(path);
  
  	/* look for a conflicting sequence number */
  	di = btrfs_lookup_dir_index_item(trans, root, path, btrfs_ino(dir),
  					 ref_index, name, namelen, 0);
  	if (IS_ERR(di)) {
  		return PTR_ERR(di);
  	} else if (di) {
  		ret = drop_one_dir_item(trans, root, path, dir, di);
  		if (ret)
  			return ret;
  	}
  	btrfs_release_path(path);
  
  	/* look for a conflicting name */
  	di = btrfs_lookup_dir_item(trans, root, path, btrfs_ino(dir),
  				   name, namelen, 0);
  	if (IS_ERR(di)) {
  		return PTR_ERR(di);
  	} else if (di) {
  		ret = drop_one_dir_item(trans, root, path, dir, di);
  		if (ret)
  			return ret;
  	}
  	btrfs_release_path(path);
  
  	return 0;
  }
  
  static int extref_get_fields(struct extent_buffer *eb, unsigned long ref_ptr,
  			     u32 *namelen, char **name, u64 *index,
  			     u64 *parent_objectid)
  {
  	struct btrfs_inode_extref *extref;
  
  	extref = (struct btrfs_inode_extref *)ref_ptr;
  
  	*namelen = btrfs_inode_extref_name_len(eb, extref);
  	*name = kmalloc(*namelen, GFP_NOFS);
  	if (*name == NULL)
  		return -ENOMEM;
  
  	read_extent_buffer(eb, *name, (unsigned long)&extref->name,
  			   *namelen);
  
  	if (index)
  		*index = btrfs_inode_extref_index(eb, extref);
  	if (parent_objectid)
  		*parent_objectid = btrfs_inode_extref_parent(eb, extref);
  
  	return 0;
  }
  
  static int ref_get_fields(struct extent_buffer *eb, unsigned long ref_ptr,
  			  u32 *namelen, char **name, u64 *index)
  {
  	struct btrfs_inode_ref *ref;
  
  	ref = (struct btrfs_inode_ref *)ref_ptr;
  
  	*namelen = btrfs_inode_ref_name_len(eb, ref);
  	*name = kmalloc(*namelen, GFP_NOFS);
  	if (*name == NULL)
  		return -ENOMEM;
  
  	read_extent_buffer(eb, *name, (unsigned long)(ref + 1), *namelen);
  
  	if (index)
  		*index = btrfs_inode_ref_index(eb, ref);
  
  	return 0;
  }
  
  /*
   * Take an inode reference item from the log tree and iterate all names from the
   * inode reference item in the subvolume tree with the same key (if it exists).
   * For any name that is not in the inode reference item from the log tree, do a
   * proper unlink of that name (that is, remove its entry from the inode
   * reference item and both dir index keys).
   */
  static int unlink_old_inode_refs(struct btrfs_trans_handle *trans,
  				 struct btrfs_root *root,
  				 struct btrfs_path *path,
  				 struct btrfs_inode *inode,
  				 struct extent_buffer *log_eb,
  				 int log_slot,
  				 struct btrfs_key *key)
  {
  	int ret;
  	unsigned long ref_ptr;
  	unsigned long ref_end;
  	struct extent_buffer *eb;
  
  again:
  	btrfs_release_path(path);
  	ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
  	if (ret > 0) {
  		ret = 0;
  		goto out;
  	}
  	if (ret < 0)
  		goto out;
  
  	eb = path->nodes[0];
  	ref_ptr = btrfs_item_ptr_offset(eb, path->slots[0]);
  	ref_end = ref_ptr + btrfs_item_size_nr(eb, path->slots[0]);
  	while (ref_ptr < ref_end) {
  		char *name = NULL;
  		int namelen;
  		u64 parent_id;
  
  		if (key->type == BTRFS_INODE_EXTREF_KEY) {
  			ret = extref_get_fields(eb, ref_ptr, &namelen, &name,
  						NULL, &parent_id);
  		} else {
  			parent_id = key->offset;
  			ret = ref_get_fields(eb, ref_ptr, &namelen, &name,
  					     NULL);
  		}
  		if (ret)
  			goto out;
  
  		if (key->type == BTRFS_INODE_EXTREF_KEY)
  			ret = !!btrfs_find_name_in_ext_backref(log_eb, log_slot,
  							       parent_id, name,
  							       namelen);
  		else
  			ret = !!btrfs_find_name_in_backref(log_eb, log_slot,
  							   name, namelen);
  
  		if (!ret) {
  			struct inode *dir;
  
  			btrfs_release_path(path);
  			dir = read_one_inode(root, parent_id);
  			if (!dir) {
  				ret = -ENOENT;
  				kfree(name);
  				goto out;
  			}
  			ret = btrfs_unlink_inode(trans, root, BTRFS_I(dir),
  						 inode, name, namelen);
  			kfree(name);
  			iput(dir);
  			if (ret)
  				goto out;
  			goto again;
  		}
  
  		kfree(name);
  		ref_ptr += namelen;
  		if (key->type == BTRFS_INODE_EXTREF_KEY)
  			ref_ptr += sizeof(struct btrfs_inode_extref);
  		else
  			ref_ptr += sizeof(struct btrfs_inode_ref);
  	}
  	ret = 0;
   out:
  	btrfs_release_path(path);
  	return ret;
  }
  
  static int btrfs_inode_ref_exists(struct inode *inode, struct inode *dir,
  				  const u8 ref_type, const char *name,
  				  const int namelen)
  {
  	struct btrfs_key key;
  	struct btrfs_path *path;
  	const u64 parent_id = btrfs_ino(BTRFS_I(dir));
  	int ret;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	key.objectid = btrfs_ino(BTRFS_I(inode));
  	key.type = ref_type;
  	if (key.type == BTRFS_INODE_REF_KEY)
  		key.offset = parent_id;
  	else
  		key.offset = btrfs_extref_hash(parent_id, name, namelen);
  
  	ret = btrfs_search_slot(NULL, BTRFS_I(inode)->root, &key, path, 0, 0);
  	if (ret < 0)
  		goto out;
  	if (ret > 0) {
  		ret = 0;
  		goto out;
  	}
  	if (key.type == BTRFS_INODE_EXTREF_KEY)
  		ret = !!btrfs_find_name_in_ext_backref(path->nodes[0],
  				path->slots[0], parent_id, name, namelen);
  	else
  		ret = !!btrfs_find_name_in_backref(path->nodes[0], path->slots[0],
  						   name, namelen);
  
  out:
  	btrfs_free_path(path);
  	return ret;
  }
  
  static int add_link(struct btrfs_trans_handle *trans, struct btrfs_root *root,
  		    struct inode *dir, struct inode *inode, const char *name,
  		    int namelen, u64 ref_index)
  {
  	struct btrfs_dir_item *dir_item;
  	struct btrfs_key key;
  	struct btrfs_path *path;
  	struct inode *other_inode = NULL;
  	int ret;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	dir_item = btrfs_lookup_dir_item(NULL, root, path,
  					 btrfs_ino(BTRFS_I(dir)),
  					 name, namelen, 0);
  	if (!dir_item) {
  		btrfs_release_path(path);
  		goto add_link;
  	} else if (IS_ERR(dir_item)) {
  		ret = PTR_ERR(dir_item);
  		goto out;
  	}
  
  	/*
  	 * Our inode's dentry collides with the dentry of another inode which is
  	 * in the log but not yet processed since it has a higher inode number.
  	 * So delete that other dentry.
  	 */
  	btrfs_dir_item_key_to_cpu(path->nodes[0], dir_item, &key);
  	btrfs_release_path(path);
  	other_inode = read_one_inode(root, key.objectid);
  	if (!other_inode) {
  		ret = -ENOENT;
  		goto out;
  	}
  	ret = btrfs_unlink_inode(trans, root, BTRFS_I(dir), BTRFS_I(other_inode),
  				 name, namelen);
  	if (ret)
  		goto out;
  	/*
  	 * If we dropped the link count to 0, bump it so that later the iput()
  	 * on the inode will not free it. We will fixup the link count later.
  	 */
  	if (other_inode->i_nlink == 0)
  		inc_nlink(other_inode);
  
  	ret = btrfs_run_delayed_items(trans);
  	if (ret)
  		goto out;
  add_link:
  	ret = btrfs_add_link(trans, BTRFS_I(dir), BTRFS_I(inode),
  			     name, namelen, 0, ref_index);
  out:
  	iput(other_inode);
  	btrfs_free_path(path);
  
  	return ret;
  }
  
  /*
   * replay one inode back reference item found in the log tree.
   * eb, slot and key refer to the buffer and key found in the log tree.
   * root is the destination we are replaying into, and path is for temp
   * use by this function.  (it should be released on return).
   */
  static noinline int add_inode_ref(struct btrfs_trans_handle *trans,
  				  struct btrfs_root *root,
  				  struct btrfs_root *log,
  				  struct btrfs_path *path,
  				  struct extent_buffer *eb, int slot,
  				  struct btrfs_key *key)
  {
  	struct inode *dir = NULL;
  	struct inode *inode = NULL;
  	unsigned long ref_ptr;
  	unsigned long ref_end;
  	char *name = NULL;
  	int namelen;
  	int ret;
  	int search_done = 0;
  	int log_ref_ver = 0;
  	u64 parent_objectid;
  	u64 inode_objectid;
  	u64 ref_index = 0;
  	int ref_struct_size;
  
  	ref_ptr = btrfs_item_ptr_offset(eb, slot);
  	ref_end = ref_ptr + btrfs_item_size_nr(eb, slot);
  
  	if (key->type == BTRFS_INODE_EXTREF_KEY) {
  		struct btrfs_inode_extref *r;
  
  		ref_struct_size = sizeof(struct btrfs_inode_extref);
  		log_ref_ver = 1;
  		r = (struct btrfs_inode_extref *)ref_ptr;
  		parent_objectid = btrfs_inode_extref_parent(eb, r);
  	} else {
  		ref_struct_size = sizeof(struct btrfs_inode_ref);
  		parent_objectid = key->offset;
  	}
  	inode_objectid = key->objectid;
  
  	/*
  	 * it is possible that we didn't log all the parent directories
  	 * for a given inode.  If we don't find the dir, just don't
  	 * copy the back ref in.  The link count fixup code will take
  	 * care of the rest
  	 */
  	dir = read_one_inode(root, parent_objectid);
  	if (!dir) {
  		ret = -ENOENT;
  		goto out;
  	}
  
  	inode = read_one_inode(root, inode_objectid);
  	if (!inode) {
  		ret = -EIO;
  		goto out;
  	}
  
  	while (ref_ptr < ref_end) {
  		if (log_ref_ver) {
  			ret = extref_get_fields(eb, ref_ptr, &namelen, &name,
  						&ref_index, &parent_objectid);
  			/*
  			 * parent object can change from one array
  			 * item to another.
  			 */
  			if (!dir)
  				dir = read_one_inode(root, parent_objectid);
  			if (!dir) {
  				ret = -ENOENT;
  				goto out;
  			}
  		} else {
  			ret = ref_get_fields(eb, ref_ptr, &namelen, &name,
  					     &ref_index);
  		}
  		if (ret)
  			goto out;
  
  		ret = inode_in_dir(root, path, btrfs_ino(BTRFS_I(dir)),
  				   btrfs_ino(BTRFS_I(inode)), ref_index,
  				   name, namelen);
  		if (ret < 0) {
  			goto out;
  		} else if (ret == 0) {
  			/*
  			 * look for a conflicting back reference in the
  			 * metadata. if we find one we have to unlink that name
  			 * of the file before we add our new link.  Later on, we
  			 * overwrite any existing back reference, and we don't
  			 * want to create dangling pointers in the directory.
  			 */
  
  			if (!search_done) {
  				ret = __add_inode_ref(trans, root, path, log,
  						      BTRFS_I(dir),
  						      BTRFS_I(inode),
  						      inode_objectid,
  						      parent_objectid,
  						      ref_index, name, namelen,
  						      &search_done);
  				if (ret) {
  					if (ret == 1)
  						ret = 0;
  					goto out;
  				}
  			}
  
  			/*
  			 * If a reference item already exists for this inode
  			 * with the same parent and name, but different index,
  			 * drop it and the corresponding directory index entries
  			 * from the parent before adding the new reference item
  			 * and dir index entries, otherwise we would fail with
  			 * -EEXIST returned from btrfs_add_link() below.
  			 */
  			ret = btrfs_inode_ref_exists(inode, dir, key->type,
  						     name, namelen);
  			if (ret > 0) {
  				ret = btrfs_unlink_inode(trans, root,
  							 BTRFS_I(dir),
  							 BTRFS_I(inode),
  							 name, namelen);
  				/*
  				 * If we dropped the link count to 0, bump it so
  				 * that later the iput() on the inode will not
  				 * free it. We will fixup the link count later.
  				 */
  				if (!ret && inode->i_nlink == 0)
  					inc_nlink(inode);
  			}
  			if (ret < 0)
  				goto out;
  
  			/* insert our name */
  			ret = add_link(trans, root, dir, inode, name, namelen,
  				       ref_index);
  			if (ret)
  				goto out;
  
  			ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
  			if (ret)
  				goto out;
  		}
  		/* Else, ret == 1, we already have a perfect match, we're done. */
  
  		ref_ptr = (unsigned long)(ref_ptr + ref_struct_size) + namelen;
  		kfree(name);
  		name = NULL;
  		if (log_ref_ver) {
  			iput(dir);
  			dir = NULL;
  		}
  	}
  
  	/*
  	 * Before we overwrite the inode reference item in the subvolume tree
  	 * with the item from the log tree, we must unlink all names from the
  	 * parent directory that are in the subvolume's tree inode reference
  	 * item, otherwise we end up with an inconsistent subvolume tree where
  	 * dir index entries exist for a name but there is no inode reference
  	 * item with the same name.
  	 */
  	ret = unlink_old_inode_refs(trans, root, path, BTRFS_I(inode), eb, slot,
  				    key);
  	if (ret)
  		goto out;
  
  	/* finally write the back reference in the inode */
  	ret = overwrite_item(trans, root, path, eb, slot, key);
  out:
  	btrfs_release_path(path);
  	kfree(name);
  	iput(dir);
  	iput(inode);
  	return ret;
  }
  
  static int count_inode_extrefs(struct btrfs_root *root,
  		struct btrfs_inode *inode, struct btrfs_path *path)
  {
  	int ret = 0;
  	int name_len;
  	unsigned int nlink = 0;
  	u32 item_size;
  	u32 cur_offset = 0;
  	u64 inode_objectid = btrfs_ino(inode);
  	u64 offset = 0;
  	unsigned long ptr;
  	struct btrfs_inode_extref *extref;
  	struct extent_buffer *leaf;
  
  	while (1) {
  		ret = btrfs_find_one_extref(root, inode_objectid, offset, path,
  					    &extref, &offset);
  		if (ret)
  			break;
  
  		leaf = path->nodes[0];
  		item_size = btrfs_item_size_nr(leaf, path->slots[0]);
  		ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
  		cur_offset = 0;
  
  		while (cur_offset < item_size) {
  			extref = (struct btrfs_inode_extref *) (ptr + cur_offset);
  			name_len = btrfs_inode_extref_name_len(leaf, extref);
  
  			nlink++;
  
  			cur_offset += name_len + sizeof(*extref);
  		}
  
  		offset++;
  		btrfs_release_path(path);
  	}
  	btrfs_release_path(path);
  
  	if (ret < 0 && ret != -ENOENT)
  		return ret;
  	return nlink;
  }
  
  static int count_inode_refs(struct btrfs_root *root,
  			struct btrfs_inode *inode, struct btrfs_path *path)
  {
  	int ret;
  	struct btrfs_key key;
  	unsigned int nlink = 0;
  	unsigned long ptr;
  	unsigned long ptr_end;
  	int name_len;
  	u64 ino = btrfs_ino(inode);
  
  	key.objectid = ino;
  	key.type = BTRFS_INODE_REF_KEY;
  	key.offset = (u64)-1;
  
  	while (1) {
  		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
  		if (ret < 0)
  			break;
  		if (ret > 0) {
  			if (path->slots[0] == 0)
  				break;
  			path->slots[0]--;
  		}
  process_slot:
  		btrfs_item_key_to_cpu(path->nodes[0], &key,
  				      path->slots[0]);
  		if (key.objectid != ino ||
  		    key.type != BTRFS_INODE_REF_KEY)
  			break;
  		ptr = btrfs_item_ptr_offset(path->nodes[0], path->slots[0]);
  		ptr_end = ptr + btrfs_item_size_nr(path->nodes[0],
  						   path->slots[0]);
  		while (ptr < ptr_end) {
  			struct btrfs_inode_ref *ref;
  
  			ref = (struct btrfs_inode_ref *)ptr;
  			name_len = btrfs_inode_ref_name_len(path->nodes[0],
  							    ref);
  			ptr = (unsigned long)(ref + 1) + name_len;
  			nlink++;
  		}
  
  		if (key.offset == 0)
  			break;
  		if (path->slots[0] > 0) {
  			path->slots[0]--;
  			goto process_slot;
  		}
  		key.offset--;
  		btrfs_release_path(path);
  	}
  	btrfs_release_path(path);
  
  	return nlink;
  }
  
  /*
   * There are a few corners where the link count of the file can't
   * be properly maintained during replay.  So, instead of adding
   * lots of complexity to the log code, we just scan the backrefs
   * for any file that has been through replay.
   *
   * The scan will update the link count on the inode to reflect the
   * number of back refs found.  If it goes down to zero, the iput
   * will free the inode.
   */
  static noinline int fixup_inode_link_count(struct btrfs_trans_handle *trans,
  					   struct btrfs_root *root,
  					   struct inode *inode)
  {
  	struct btrfs_path *path;
  	int ret;
  	u64 nlink = 0;
  	u64 ino = btrfs_ino(BTRFS_I(inode));
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	ret = count_inode_refs(root, BTRFS_I(inode), path);
  	if (ret < 0)
  		goto out;
  
  	nlink = ret;
  
  	ret = count_inode_extrefs(root, BTRFS_I(inode), path);
  	if (ret < 0)
  		goto out;
  
  	nlink += ret;
  
  	ret = 0;
  
  	if (nlink != inode->i_nlink) {
  		set_nlink(inode, nlink);
  		ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
  		if (ret)
  			goto out;
  	}
  	BTRFS_I(inode)->index_cnt = (u64)-1;
  
  	if (inode->i_nlink == 0) {
  		if (S_ISDIR(inode->i_mode)) {
  			ret = replay_dir_deletes(trans, root, NULL, path,
  						 ino, 1);
  			if (ret)
  				goto out;
  		}
  		ret = btrfs_insert_orphan_item(trans, root, ino);
  		if (ret == -EEXIST)
  			ret = 0;
  	}
  
  out:
  	btrfs_free_path(path);
  	return ret;
  }
  
  static noinline int fixup_inode_link_counts(struct btrfs_trans_handle *trans,
  					    struct btrfs_root *root,
  					    struct btrfs_path *path)
  {
  	int ret;
  	struct btrfs_key key;
  	struct inode *inode;
  
  	key.objectid = BTRFS_TREE_LOG_FIXUP_OBJECTID;
  	key.type = BTRFS_ORPHAN_ITEM_KEY;
  	key.offset = (u64)-1;
  	while (1) {
  		ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
  		if (ret < 0)
  			break;
  
  		if (ret == 1) {
  			ret = 0;
  			if (path->slots[0] == 0)
  				break;
  			path->slots[0]--;
  		}
  
  		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
  		if (key.objectid != BTRFS_TREE_LOG_FIXUP_OBJECTID ||
  		    key.type != BTRFS_ORPHAN_ITEM_KEY)
  			break;
  
  		ret = btrfs_del_item(trans, root, path);
  		if (ret)
  			break;
  
  		btrfs_release_path(path);
  		inode = read_one_inode(root, key.offset);
  		if (!inode) {
  			ret = -EIO;
  			break;
  		}
  
  		ret = fixup_inode_link_count(trans, root, inode);
  		iput(inode);
  		if (ret)
  			break;
  
  		/*
  		 * fixup on a directory may create new entries,
  		 * make sure we always look for the highset possible
  		 * offset
  		 */
  		key.offset = (u64)-1;
  	}
  	btrfs_release_path(path);
  	return ret;
  }
  
  
  /*
   * record a given inode in the fixup dir so we can check its link
   * count when replay is done.  The link count is incremented here
   * so the inode won't go away until we check it
   */
  static noinline int link_to_fixup_dir(struct btrfs_trans_handle *trans,
  				      struct btrfs_root *root,
  				      struct btrfs_path *path,
  				      u64 objectid)
  {
  	struct btrfs_key key;
  	int ret = 0;
  	struct inode *inode;
  
  	inode = read_one_inode(root, objectid);
  	if (!inode)
  		return -EIO;
  
  	key.objectid = BTRFS_TREE_LOG_FIXUP_OBJECTID;
  	key.type = BTRFS_ORPHAN_ITEM_KEY;
  	key.offset = objectid;
  
  	ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
  
  	btrfs_release_path(path);
  	if (ret == 0) {
  		if (!inode->i_nlink)
  			set_nlink(inode, 1);
  		else
  			inc_nlink(inode);
  		ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
  	} else if (ret == -EEXIST) {
  		ret = 0;
  	}
  	iput(inode);
  
  	return ret;
  }
  
  /*
   * when replaying the log for a directory, we only insert names
   * for inodes that actually exist.  This means an fsync on a directory
   * does not implicitly fsync all the new files in it
   */
  static noinline int insert_one_name(struct btrfs_trans_handle *trans,
  				    struct btrfs_root *root,
  				    u64 dirid, u64 index,
  				    char *name, int name_len,
  				    struct btrfs_key *location)
  {
  	struct inode *inode;
  	struct inode *dir;
  	int ret;
  
  	inode = read_one_inode(root, location->objectid);
  	if (!inode)
  		return -ENOENT;
  
  	dir = read_one_inode(root, dirid);
  	if (!dir) {
  		iput(inode);
  		return -EIO;
  	}
  
  	ret = btrfs_add_link(trans, BTRFS_I(dir), BTRFS_I(inode), name,
  			name_len, 1, index);
  
  	/* FIXME, put inode into FIXUP list */
  
  	iput(inode);
  	iput(dir);
  	return ret;
  }
  
  /*
   * take a single entry in a log directory item and replay it into
   * the subvolume.
   *
   * if a conflicting item exists in the subdirectory already,
   * the inode it points to is unlinked and put into the link count
   * fix up tree.
   *
   * If a name from the log points to a file or directory that does
   * not exist in the FS, it is skipped.  fsyncs on directories
   * do not force down inodes inside that directory, just changes to the
   * names or unlinks in a directory.
   *
   * Returns < 0 on error, 0 if the name wasn't replayed (dentry points to a
   * non-existing inode) and 1 if the name was replayed.
   */
  static noinline int replay_one_name(struct btrfs_trans_handle *trans,
  				    struct btrfs_root *root,
  				    struct btrfs_path *path,
  				    struct extent_buffer *eb,
  				    struct btrfs_dir_item *di,
  				    struct btrfs_key *key)
  {
  	char *name;
  	int name_len;
  	struct btrfs_dir_item *dst_di;
  	struct btrfs_key found_key;
  	struct btrfs_key log_key;
  	struct inode *dir;
  	u8 log_type;
  	bool exists;
  	int ret;
  	bool update_size = (key->type == BTRFS_DIR_INDEX_KEY);
  	bool name_added = false;
  
  	dir = read_one_inode(root, key->objectid);
  	if (!dir)
  		return -EIO;
  
  	name_len = btrfs_dir_name_len(eb, di);
  	name = kmalloc(name_len, GFP_NOFS);
  	if (!name) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	log_type = btrfs_dir_type(eb, di);
  	read_extent_buffer(eb, name, (unsigned long)(di + 1),
  		   name_len);
  
  	btrfs_dir_item_key_to_cpu(eb, di, &log_key);
  	ret = btrfs_lookup_inode(trans, root, path, &log_key, 0);
  	btrfs_release_path(path);
  	if (ret < 0)
  		goto out;
  	exists = (ret == 0);
  	ret = 0;
  
  	if (key->type == BTRFS_DIR_ITEM_KEY) {
  		dst_di = btrfs_lookup_dir_item(trans, root, path, key->objectid,
  				       name, name_len, 1);
  	} else if (key->type == BTRFS_DIR_INDEX_KEY) {
  		dst_di = btrfs_lookup_dir_index_item(trans, root, path,
  						     key->objectid,
  						     key->offset, name,
  						     name_len, 1);
  	} else {
  		/* Corruption */
  		ret = -EINVAL;
  		goto out;
  	}
  
  	if (IS_ERR(dst_di)) {
  		ret = PTR_ERR(dst_di);
  		goto out;
  	} else if (!dst_di) {
  		/* we need a sequence number to insert, so we only
  		 * do inserts for the BTRFS_DIR_INDEX_KEY types
  		 */
  		if (key->type != BTRFS_DIR_INDEX_KEY)
  			goto out;
  		goto insert;
  	}
  
  	btrfs_dir_item_key_to_cpu(path->nodes[0], dst_di, &found_key);
  	/* the existing item matches the logged item */
  	if (found_key.objectid == log_key.objectid &&
  	    found_key.type == log_key.type &&
  	    found_key.offset == log_key.offset &&
  	    btrfs_dir_type(path->nodes[0], dst_di) == log_type) {
  		update_size = false;
  		goto out;
  	}
  
  	/*
  	 * don't drop the conflicting directory entry if the inode
  	 * for the new entry doesn't exist
  	 */
  	if (!exists)
  		goto out;
  
  	ret = drop_one_dir_item(trans, root, path, BTRFS_I(dir), dst_di);
  	if (ret)
  		goto out;
  
  	if (key->type == BTRFS_DIR_INDEX_KEY)
  		goto insert;
  out:
  	btrfs_release_path(path);
  	if (!ret && update_size) {
  		btrfs_i_size_write(BTRFS_I(dir), dir->i_size + name_len * 2);
  		ret = btrfs_update_inode(trans, root, BTRFS_I(dir));
  	}
  	kfree(name);
  	iput(dir);
  	if (!ret && name_added)
  		ret = 1;
  	return ret;
  
  insert:
  	/*
  	 * Check if the inode reference exists in the log for the given name,
  	 * inode and parent inode
  	 */
  	found_key.objectid = log_key.objectid;
  	found_key.type = BTRFS_INODE_REF_KEY;
  	found_key.offset = key->objectid;
  	ret = backref_in_log(root->log_root, &found_key, 0, name, name_len);
  	if (ret < 0) {
  	        goto out;
  	} else if (ret) {
  	        /* The dentry will be added later. */
  	        ret = 0;
  	        update_size = false;
  	        goto out;
  	}
  
  	found_key.objectid = log_key.objectid;
  	found_key.type = BTRFS_INODE_EXTREF_KEY;
  	found_key.offset = key->objectid;
  	ret = backref_in_log(root->log_root, &found_key, key->objectid, name,
  			     name_len);
  	if (ret < 0) {
  		goto out;
  	} else if (ret) {
  		/* The dentry will be added later. */
  		ret = 0;
  		update_size = false;
  		goto out;
  	}
  	btrfs_release_path(path);
  	ret = insert_one_name(trans, root, key->objectid, key->offset,
  			      name, name_len, &log_key);
  	if (ret && ret != -ENOENT && ret != -EEXIST)
  		goto out;
  	if (!ret)
  		name_added = true;
  	update_size = false;
  	ret = 0;
  	goto out;
  }
  
  /*
   * find all the names in a directory item and reconcile them into
   * the subvolume.  Only BTRFS_DIR_ITEM_KEY types will have more than
   * one name in a directory item, but the same code gets used for
   * both directory index types
   */
  static noinline int replay_one_dir_item(struct btrfs_trans_handle *trans,
  					struct btrfs_root *root,
  					struct btrfs_path *path,
  					struct extent_buffer *eb, int slot,
  					struct btrfs_key *key)
  {
  	int ret = 0;
  	u32 item_size = btrfs_item_size_nr(eb, slot);
  	struct btrfs_dir_item *di;
  	int name_len;
  	unsigned long ptr;
  	unsigned long ptr_end;
  	struct btrfs_path *fixup_path = NULL;
  
  	ptr = btrfs_item_ptr_offset(eb, slot);
  	ptr_end = ptr + item_size;
  	while (ptr < ptr_end) {
  		di = (struct btrfs_dir_item *)ptr;
  		name_len = btrfs_dir_name_len(eb, di);
  		ret = replay_one_name(trans, root, path, eb, di, key);
  		if (ret < 0)
  			break;
  		ptr = (unsigned long)(di + 1);
  		ptr += name_len;
  
  		/*
  		 * If this entry refers to a non-directory (directories can not
  		 * have a link count > 1) and it was added in the transaction
  		 * that was not committed, make sure we fixup the link count of
  		 * the inode it the entry points to. Otherwise something like
  		 * the following would result in a directory pointing to an
  		 * inode with a wrong link that does not account for this dir
  		 * entry:
  		 *
  		 * mkdir testdir
  		 * touch testdir/foo
  		 * touch testdir/bar
  		 * sync
  		 *
  		 * ln testdir/bar testdir/bar_link
  		 * ln testdir/foo testdir/foo_link
  		 * xfs_io -c "fsync" testdir/bar
  		 *
  		 * <power failure>
  		 *
  		 * mount fs, log replay happens
  		 *
  		 * File foo would remain with a link count of 1 when it has two
  		 * entries pointing to it in the directory testdir. This would
  		 * make it impossible to ever delete the parent directory has
  		 * it would result in stale dentries that can never be deleted.
  		 */
  		if (ret == 1 && btrfs_dir_type(eb, di) != BTRFS_FT_DIR) {
  			struct btrfs_key di_key;
  
  			if (!fixup_path) {
  				fixup_path = btrfs_alloc_path();
  				if (!fixup_path) {
  					ret = -ENOMEM;
  					break;
  				}
  			}
  
  			btrfs_dir_item_key_to_cpu(eb, di, &di_key);
  			ret = link_to_fixup_dir(trans, root, fixup_path,
  						di_key.objectid);
  			if (ret)
  				break;
  		}
  		ret = 0;
  	}
  	btrfs_free_path(fixup_path);
  	return ret;
  }
  
  /*
   * directory replay has two parts.  There are the standard directory
   * items in the log copied from the subvolume, and range items
   * created in the log while the subvolume was logged.
   *
   * The range items tell us which parts of the key space the log
   * is authoritative for.  During replay, if a key in the subvolume
   * directory is in a logged range item, but not actually in the log
   * that means it was deleted from the directory before the fsync
   * and should be removed.
   */
  static noinline int find_dir_range(struct btrfs_root *root,
  				   struct btrfs_path *path,
  				   u64 dirid, int key_type,
  				   u64 *start_ret, u64 *end_ret)
  {
  	struct btrfs_key key;
  	u64 found_end;
  	struct btrfs_dir_log_item *item;
  	int ret;
  	int nritems;
  
  	if (*start_ret == (u64)-1)
  		return 1;
  
  	key.objectid = dirid;
  	key.type = key_type;
  	key.offset = *start_ret;
  
  	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
  	if (ret < 0)
  		goto out;
  	if (ret > 0) {
  		if (path->slots[0] == 0)
  			goto out;
  		path->slots[0]--;
  	}
  	if (ret != 0)
  		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
  
  	if (key.type != key_type || key.objectid != dirid) {
  		ret = 1;
  		goto next;
  	}
  	item = btrfs_item_ptr(path->nodes[0], path->slots[0],
  			      struct btrfs_dir_log_item);
  	found_end = btrfs_dir_log_end(path->nodes[0], item);
  
  	if (*start_ret >= key.offset && *start_ret <= found_end) {
  		ret = 0;
  		*start_ret = key.offset;
  		*end_ret = found_end;
  		goto out;
  	}
  	ret = 1;
  next:
  	/* check the next slot in the tree to see if it is a valid item */
  	nritems = btrfs_header_nritems(path->nodes[0]);
  	path->slots[0]++;
  	if (path->slots[0] >= nritems) {
  		ret = btrfs_next_leaf(root, path);
  		if (ret)
  			goto out;
  	}
  
  	btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
  
  	if (key.type != key_type || key.objectid != dirid) {
  		ret = 1;
  		goto out;
  	}
  	item = btrfs_item_ptr(path->nodes[0], path->slots[0],
  			      struct btrfs_dir_log_item);
  	found_end = btrfs_dir_log_end(path->nodes[0], item);
  	*start_ret = key.offset;
  	*end_ret = found_end;
  	ret = 0;
  out:
  	btrfs_release_path(path);
  	return ret;
  }
  
  /*
   * this looks for a given directory item in the log.  If the directory
   * item is not in the log, the item is removed and the inode it points
   * to is unlinked
   */
  static noinline int check_item_in_log(struct btrfs_trans_handle *trans,
  				      struct btrfs_root *root,
  				      struct btrfs_root *log,
  				      struct btrfs_path *path,
  				      struct btrfs_path *log_path,
  				      struct inode *dir,
  				      struct btrfs_key *dir_key)
  {
  	int ret;
  	struct extent_buffer *eb;
  	int slot;
  	u32 item_size;
  	struct btrfs_dir_item *di;
  	struct btrfs_dir_item *log_di;
  	int name_len;
  	unsigned long ptr;
  	unsigned long ptr_end;
  	char *name;
  	struct inode *inode;
  	struct btrfs_key location;
  
  again:
  	eb = path->nodes[0];
  	slot = path->slots[0];
  	item_size = btrfs_item_size_nr(eb, slot);
  	ptr = btrfs_item_ptr_offset(eb, slot);
  	ptr_end = ptr + item_size;
  	while (ptr < ptr_end) {
  		di = (struct btrfs_dir_item *)ptr;
  		name_len = btrfs_dir_name_len(eb, di);
  		name = kmalloc(name_len, GFP_NOFS);
  		if (!name) {
  			ret = -ENOMEM;
  			goto out;
  		}
  		read_extent_buffer(eb, name, (unsigned long)(di + 1),
  				  name_len);
  		log_di = NULL;
  		if (log && dir_key->type == BTRFS_DIR_ITEM_KEY) {
  			log_di = btrfs_lookup_dir_item(trans, log, log_path,
  						       dir_key->objectid,
  						       name, name_len, 0);
  		} else if (log && dir_key->type == BTRFS_DIR_INDEX_KEY) {
  			log_di = btrfs_lookup_dir_index_item(trans, log,
  						     log_path,
  						     dir_key->objectid,
  						     dir_key->offset,
  						     name, name_len, 0);
  		}
  		if (!log_di) {
  			btrfs_dir_item_key_to_cpu(eb, di, &location);
  			btrfs_release_path(path);
  			btrfs_release_path(log_path);
  			inode = read_one_inode(root, location.objectid);
  			if (!inode) {
  				kfree(name);
  				return -EIO;
  			}
  
  			ret = link_to_fixup_dir(trans, root,
  						path, location.objectid);
  			if (ret) {
  				kfree(name);
  				iput(inode);
  				goto out;
  			}
  
  			inc_nlink(inode);
  			ret = btrfs_unlink_inode(trans, root, BTRFS_I(dir),
  					BTRFS_I(inode), name, name_len);
  			if (!ret)
  				ret = btrfs_run_delayed_items(trans);
  			kfree(name);
  			iput(inode);
  			if (ret)
  				goto out;
  
  			/* there might still be more names under this key
  			 * check and repeat if required
  			 */
  			ret = btrfs_search_slot(NULL, root, dir_key, path,
  						0, 0);
  			if (ret == 0)
  				goto again;
  			ret = 0;
  			goto out;
  		} else if (IS_ERR(log_di)) {
  			kfree(name);
  			return PTR_ERR(log_di);
  		}
  		btrfs_release_path(log_path);
  		kfree(name);
  
  		ptr = (unsigned long)(di + 1);
  		ptr += name_len;
  	}
  	ret = 0;
  out:
  	btrfs_release_path(path);
  	btrfs_release_path(log_path);
  	return ret;
  }
  
  static int replay_xattr_deletes(struct btrfs_trans_handle *trans,
  			      struct btrfs_root *root,
  			      struct btrfs_root *log,
  			      struct btrfs_path *path,
  			      const u64 ino)
  {
  	struct btrfs_key search_key;
  	struct btrfs_path *log_path;
  	int i;
  	int nritems;
  	int ret;
  
  	log_path = btrfs_alloc_path();
  	if (!log_path)
  		return -ENOMEM;
  
  	search_key.objectid = ino;
  	search_key.type = BTRFS_XATTR_ITEM_KEY;
  	search_key.offset = 0;
  again:
  	ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
  	if (ret < 0)
  		goto out;
  process_leaf:
  	nritems = btrfs_header_nritems(path->nodes[0]);
  	for (i = path->slots[0]; i < nritems; i++) {
  		struct btrfs_key key;
  		struct btrfs_dir_item *di;
  		struct btrfs_dir_item *log_di;
  		u32 total_size;
  		u32 cur;
  
  		btrfs_item_key_to_cpu(path->nodes[0], &key, i);
  		if (key.objectid != ino || key.type != BTRFS_XATTR_ITEM_KEY) {
  			ret = 0;
  			goto out;
  		}
  
  		di = btrfs_item_ptr(path->nodes[0], i, struct btrfs_dir_item);
  		total_size = btrfs_item_size_nr(path->nodes[0], i);
  		cur = 0;
  		while (cur < total_size) {
  			u16 name_len = btrfs_dir_name_len(path->nodes[0], di);
  			u16 data_len = btrfs_dir_data_len(path->nodes[0], di);
  			u32 this_len = sizeof(*di) + name_len + data_len;
  			char *name;
  
  			name = kmalloc(name_len, GFP_NOFS);
  			if (!name) {
  				ret = -ENOMEM;
  				goto out;
  			}
  			read_extent_buffer(path->nodes[0], name,
  					   (unsigned long)(di + 1), name_len);
  
  			log_di = btrfs_lookup_xattr(NULL, log, log_path, ino,
  						    name, name_len, 0);
  			btrfs_release_path(log_path);
  			if (!log_di) {
  				/* Doesn't exist in log tree, so delete it. */
  				btrfs_release_path(path);
  				di = btrfs_lookup_xattr(trans, root, path, ino,
  							name, name_len, -1);
  				kfree(name);
  				if (IS_ERR(di)) {
  					ret = PTR_ERR(di);
  					goto out;
  				}
  				ASSERT(di);
  				ret = btrfs_delete_one_dir_name(trans, root,
  								path, di);
  				if (ret)
  					goto out;
  				btrfs_release_path(path);
  				search_key = key;
  				goto again;
  			}
  			kfree(name);
  			if (IS_ERR(log_di)) {
  				ret = PTR_ERR(log_di);
  				goto out;
  			}
  			cur += this_len;
  			di = (struct btrfs_dir_item *)((char *)di + this_len);
  		}
  	}
  	ret = btrfs_next_leaf(root, path);
  	if (ret > 0)
  		ret = 0;
  	else if (ret == 0)
  		goto process_leaf;
  out:
  	btrfs_free_path(log_path);
  	btrfs_release_path(path);
  	return ret;
  }
  
  
  /*
   * deletion replay happens before we copy any new directory items
   * out of the log or out of backreferences from inodes.  It
   * scans the log to find ranges of keys that log is authoritative for,
   * and then scans the directory to find items in those ranges that are
   * not present in the log.
   *
   * Anything we don't find in the log is unlinked and removed from the
   * directory.
   */
  static noinline int replay_dir_deletes(struct btrfs_trans_handle *trans,
  				       struct btrfs_root *root,
  				       struct btrfs_root *log,
  				       struct btrfs_path *path,
  				       u64 dirid, int del_all)
  {
  	u64 range_start;
  	u64 range_end;
  	int key_type = BTRFS_DIR_LOG_ITEM_KEY;
  	int ret = 0;
  	struct btrfs_key dir_key;
  	struct btrfs_key found_key;
  	struct btrfs_path *log_path;
  	struct inode *dir;
  
  	dir_key.objectid = dirid;
  	dir_key.type = BTRFS_DIR_ITEM_KEY;
  	log_path = btrfs_alloc_path();
  	if (!log_path)
  		return -ENOMEM;
  
  	dir = read_one_inode(root, dirid);
  	/* it isn't an error if the inode isn't there, that can happen
  	 * because we replay the deletes before we copy in the inode item
  	 * from the log
  	 */
  	if (!dir) {
  		btrfs_free_path(log_path);
  		return 0;
  	}
  again:
  	range_start = 0;
  	range_end = 0;
  	while (1) {
  		if (del_all)
  			range_end = (u64)-1;
  		else {
  			ret = find_dir_range(log, path, dirid, key_type,
  					     &range_start, &range_end);
  			if (ret < 0)
  				goto out;
  			else if (ret > 0)
  				break;
  		}
  
  		dir_key.offset = range_start;
  		while (1) {
  			int nritems;
  			ret = btrfs_search_slot(NULL, root, &dir_key, path,
  						0, 0);
  			if (ret < 0)
  				goto out;
  
  			nritems = btrfs_header_nritems(path->nodes[0]);
  			if (path->slots[0] >= nritems) {
  				ret = btrfs_next_leaf(root, path);
  				if (ret == 1)
  					break;
  				else if (ret < 0)
  					goto out;
  			}
  			btrfs_item_key_to_cpu(path->nodes[0], &found_key,
  					      path->slots[0]);
  			if (found_key.objectid != dirid ||
  			    found_key.type != dir_key.type)
  				goto next_type;
  
  			if (found_key.offset > range_end)
  				break;
  
  			ret = check_item_in_log(trans, root, log, path,
  						log_path, dir,
  						&found_key);
  			if (ret)
  				goto out;
  			if (found_key.offset == (u64)-1)
  				break;
  			dir_key.offset = found_key.offset + 1;
  		}
  		btrfs_release_path(path);
  		if (range_end == (u64)-1)
  			break;
  		range_start = range_end + 1;
  	}
  
  next_type:
  	ret = 0;
  	if (key_type == BTRFS_DIR_LOG_ITEM_KEY) {
  		key_type = BTRFS_DIR_LOG_INDEX_KEY;
  		dir_key.type = BTRFS_DIR_INDEX_KEY;
  		btrfs_release_path(path);
  		goto again;
  	}
  out:
  	btrfs_release_path(path);
  	btrfs_free_path(log_path);
  	iput(dir);
  	return ret;
  }
  
  /*
   * the process_func used to replay items from the log tree.  This
   * gets called in two different stages.  The first stage just looks
   * for inodes and makes sure they are all copied into the subvolume.
   *
   * The second stage copies all the other item types from the log into
   * the subvolume.  The two stage approach is slower, but gets rid of
   * lots of complexity around inodes referencing other inodes that exist
   * only in the log (references come from either directory items or inode
   * back refs).
   */
  static int replay_one_buffer(struct btrfs_root *log, struct extent_buffer *eb,
  			     struct walk_control *wc, u64 gen, int level)
  {
  	int nritems;
  	struct btrfs_path *path;
  	struct btrfs_root *root = wc->replay_dest;
  	struct btrfs_key key;
  	int i;
  	int ret;
  
  	ret = btrfs_read_buffer(eb, gen, level, NULL);
  	if (ret)
  		return ret;
  
  	level = btrfs_header_level(eb);
  
  	if (level != 0)
  		return 0;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	nritems = btrfs_header_nritems(eb);
  	for (i = 0; i < nritems; i++) {
  		btrfs_item_key_to_cpu(eb, &key, i);
  
  		/* inode keys are done during the first stage */
  		if (key.type == BTRFS_INODE_ITEM_KEY &&
  		    wc->stage == LOG_WALK_REPLAY_INODES) {
  			struct btrfs_inode_item *inode_item;
  			u32 mode;
  
  			inode_item = btrfs_item_ptr(eb, i,
  					    struct btrfs_inode_item);
  			/*
  			 * If we have a tmpfile (O_TMPFILE) that got fsync'ed
  			 * and never got linked before the fsync, skip it, as
  			 * replaying it is pointless since it would be deleted
  			 * later. We skip logging tmpfiles, but it's always
  			 * possible we are replaying a log created with a kernel
  			 * that used to log tmpfiles.
  			 */
  			if (btrfs_inode_nlink(eb, inode_item) == 0) {
  				wc->ignore_cur_inode = true;
  				continue;
  			} else {
  				wc->ignore_cur_inode = false;
  			}
  			ret = replay_xattr_deletes(wc->trans, root, log,
  						   path, key.objectid);
  			if (ret)
  				break;
  			mode = btrfs_inode_mode(eb, inode_item);
  			if (S_ISDIR(mode)) {
  				ret = replay_dir_deletes(wc->trans,
  					 root, log, path, key.objectid, 0);
  				if (ret)
  					break;
  			}
  			ret = overwrite_item(wc->trans, root, path,
  					     eb, i, &key);
  			if (ret)
  				break;
  
  			/*
  			 * Before replaying extents, truncate the inode to its
  			 * size. We need to do it now and not after log replay
  			 * because before an fsync we can have prealloc extents
  			 * added beyond the inode's i_size. If we did it after,
  			 * through orphan cleanup for example, we would drop
  			 * those prealloc extents just after replaying them.
  			 */
  			if (S_ISREG(mode)) {
  				struct btrfs_drop_extents_args drop_args = { 0 };
  				struct inode *inode;
  				u64 from;
  
  				inode = read_one_inode(root, key.objectid);
  				if (!inode) {
  					ret = -EIO;
  					break;
  				}
  				from = ALIGN(i_size_read(inode),
  					     root->fs_info->sectorsize);
  				drop_args.start = from;
  				drop_args.end = (u64)-1;
  				drop_args.drop_cache = true;
  				ret = btrfs_drop_extents(wc->trans, root,
  							 BTRFS_I(inode),
  							 &drop_args);
  				if (!ret) {
  					inode_sub_bytes(inode,
  							drop_args.bytes_found);
  					/* Update the inode's nbytes. */
  					ret = btrfs_update_inode(wc->trans,
  							root, BTRFS_I(inode));
  				}
  				iput(inode);
  				if (ret)
  					break;
  			}
  
  			ret = link_to_fixup_dir(wc->trans, root,
  						path, key.objectid);
  			if (ret)
  				break;
  		}
  
  		if (wc->ignore_cur_inode)
  			continue;
  
  		if (key.type == BTRFS_DIR_INDEX_KEY &&
  		    wc->stage == LOG_WALK_REPLAY_DIR_INDEX) {
  			ret = replay_one_dir_item(wc->trans, root, path,
  						  eb, i, &key);
  			if (ret)
  				break;
  		}
  
  		if (wc->stage < LOG_WALK_REPLAY_ALL)
  			continue;
  
  		/* these keys are simply copied */
  		if (key.type == BTRFS_XATTR_ITEM_KEY) {
  			ret = overwrite_item(wc->trans, root, path,
  					     eb, i, &key);
  			if (ret)
  				break;
  		} else if (key.type == BTRFS_INODE_REF_KEY ||
  			   key.type == BTRFS_INODE_EXTREF_KEY) {
  			ret = add_inode_ref(wc->trans, root, log, path,
  					    eb, i, &key);
  			if (ret && ret != -ENOENT)
  				break;
  			ret = 0;
  		} else if (key.type == BTRFS_EXTENT_DATA_KEY) {
  			ret = replay_one_extent(wc->trans, root, path,
  						eb, i, &key);
  			if (ret)
  				break;
  		} else if (key.type == BTRFS_DIR_ITEM_KEY) {
  			ret = replay_one_dir_item(wc->trans, root, path,
  						  eb, i, &key);
  			if (ret)
  				break;
  		}
  	}
  	btrfs_free_path(path);
  	return ret;
  }
  
  /*
   * Correctly adjust the reserved bytes occupied by a log tree extent buffer
   */
  static void unaccount_log_buffer(struct btrfs_fs_info *fs_info, u64 start)
  {
  	struct btrfs_block_group *cache;
  
  	cache = btrfs_lookup_block_group(fs_info, start);
  	if (!cache) {
  		btrfs_err(fs_info, "unable to find block group for %llu", start);
  		return;
  	}
  
  	spin_lock(&cache->space_info->lock);
  	spin_lock(&cache->lock);
  	cache->reserved -= fs_info->nodesize;
  	cache->space_info->bytes_reserved -= fs_info->nodesize;
  	spin_unlock(&cache->lock);
  	spin_unlock(&cache->space_info->lock);
  
  	btrfs_put_block_group(cache);
  }
  
  static noinline int walk_down_log_tree(struct btrfs_trans_handle *trans,
  				   struct btrfs_root *root,
  				   struct btrfs_path *path, int *level,
  				   struct walk_control *wc)
  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	u64 bytenr;
  	u64 ptr_gen;
  	struct extent_buffer *next;
  	struct extent_buffer *cur;
  	u32 blocksize;
  	int ret = 0;
  
  	while (*level > 0) {
  		struct btrfs_key first_key;
  
  		cur = path->nodes[*level];
  
  		WARN_ON(btrfs_header_level(cur) != *level);
  
  		if (path->slots[*level] >=
  		    btrfs_header_nritems(cur))
  			break;
  
  		bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
  		ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);
  		btrfs_node_key_to_cpu(cur, &first_key, path->slots[*level]);
  		blocksize = fs_info->nodesize;
  
  		next = btrfs_find_create_tree_block(fs_info, bytenr,
  						    btrfs_header_owner(cur),
  						    *level - 1);
  		if (IS_ERR(next))
  			return PTR_ERR(next);
  
  		if (*level == 1) {
  			ret = wc->process_func(root, next, wc, ptr_gen,
  					       *level - 1);
  			if (ret) {
  				free_extent_buffer(next);
  				return ret;
  			}
  
  			path->slots[*level]++;
  			if (wc->free) {
  				ret = btrfs_read_buffer(next, ptr_gen,
  							*level - 1, &first_key);
  				if (ret) {
  					free_extent_buffer(next);
  					return ret;
  				}
  
  				if (trans) {
  					btrfs_tree_lock(next);
  					btrfs_clean_tree_block(next);
  					btrfs_wait_tree_block_writeback(next);
  					btrfs_tree_unlock(next);
  					ret = btrfs_pin_reserved_extent(trans,
  							bytenr, blocksize);
  					if (ret) {
  						free_extent_buffer(next);
  						return ret;
  					}
  					btrfs_redirty_list_add(
  						trans->transaction, next);
  				} else {
  					if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
  						clear_extent_buffer_dirty(next);
  					unaccount_log_buffer(fs_info, bytenr);
  				}
  			}
  			free_extent_buffer(next);
  			continue;
  		}
  		ret = btrfs_read_buffer(next, ptr_gen, *level - 1, &first_key);
  		if (ret) {
  			free_extent_buffer(next);
  			return ret;
  		}
  
  		if (path->nodes[*level-1])
  			free_extent_buffer(path->nodes[*level-1]);
  		path->nodes[*level-1] = next;
  		*level = btrfs_header_level(next);
  		path->slots[*level] = 0;
  		cond_resched();
  	}
  	path->slots[*level] = btrfs_header_nritems(path->nodes[*level]);
  
  	cond_resched();
  	return 0;
  }
  
  static noinline int walk_up_log_tree(struct btrfs_trans_handle *trans,
  				 struct btrfs_root *root,
  				 struct btrfs_path *path, int *level,
  				 struct walk_control *wc)
  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	int i;
  	int slot;
  	int ret;
  
  	for (i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
  		slot = path->slots[i];
  		if (slot + 1 < btrfs_header_nritems(path->nodes[i])) {
  			path->slots[i]++;
  			*level = i;
  			WARN_ON(*level == 0);
  			return 0;
  		} else {
  			ret = wc->process_func(root, path->nodes[*level], wc,
  				 btrfs_header_generation(path->nodes[*level]),
  				 *level);
  			if (ret)
  				return ret;
  
  			if (wc->free) {
  				struct extent_buffer *next;
  
  				next = path->nodes[*level];
  
  				if (trans) {
  					btrfs_tree_lock(next);
  					btrfs_clean_tree_block(next);
  					btrfs_wait_tree_block_writeback(next);
  					btrfs_tree_unlock(next);
  					ret = btrfs_pin_reserved_extent(trans,
  						     path->nodes[*level]->start,
  						     path->nodes[*level]->len);
  					if (ret)
  						return ret;
  					btrfs_redirty_list_add(trans->transaction,
  							       next);
  				} else {
  					if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
  						clear_extent_buffer_dirty(next);
  
  					unaccount_log_buffer(fs_info,
  						path->nodes[*level]->start);
  				}
  			}
  			free_extent_buffer(path->nodes[*level]);
  			path->nodes[*level] = NULL;
  			*level = i + 1;
  		}
  	}
  	return 1;
  }
  
  /*
   * drop the reference count on the tree rooted at 'snap'.  This traverses
   * the tree freeing any blocks that have a ref count of zero after being
   * decremented.
   */
  static int walk_log_tree(struct btrfs_trans_handle *trans,
  			 struct btrfs_root *log, struct walk_control *wc)
  {
  	struct btrfs_fs_info *fs_info = log->fs_info;
  	int ret = 0;
  	int wret;
  	int level;
  	struct btrfs_path *path;
  	int orig_level;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	level = btrfs_header_level(log->node);
  	orig_level = level;
  	path->nodes[level] = log->node;
  	atomic_inc(&log->node->refs);
  	path->slots[level] = 0;
  
  	while (1) {
  		wret = walk_down_log_tree(trans, log, path, &level, wc);
  		if (wret > 0)
  			break;
  		if (wret < 0) {
  			ret = wret;
  			goto out;
  		}
  
  		wret = walk_up_log_tree(trans, log, path, &level, wc);
  		if (wret > 0)
  			break;
  		if (wret < 0) {
  			ret = wret;
  			goto out;
  		}
  	}
  
  	/* was the root node processed? if not, catch it here */
  	if (path->nodes[orig_level]) {
  		ret = wc->process_func(log, path->nodes[orig_level], wc,
  			 btrfs_header_generation(path->nodes[orig_level]),
  			 orig_level);
  		if (ret)
  			goto out;
  		if (wc->free) {
  			struct extent_buffer *next;
  
  			next = path->nodes[orig_level];
  
  			if (trans) {
  				btrfs_tree_lock(next);
  				btrfs_clean_tree_block(next);
  				btrfs_wait_tree_block_writeback(next);
  				btrfs_tree_unlock(next);
  				ret = btrfs_pin_reserved_extent(trans,
  						next->start, next->len);
  				if (ret)
  					goto out;
  				btrfs_redirty_list_add(trans->transaction, next);
  			} else {
  				if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
  					clear_extent_buffer_dirty(next);
  				unaccount_log_buffer(fs_info, next->start);
  			}
  		}
  	}
  
  out:
  	btrfs_free_path(path);
  	return ret;
  }
  
  /*
   * helper function to update the item for a given subvolumes log root
   * in the tree of log roots
   */
  static int update_log_root(struct btrfs_trans_handle *trans,
  			   struct btrfs_root *log,
  			   struct btrfs_root_item *root_item)
  {
  	struct btrfs_fs_info *fs_info = log->fs_info;
  	int ret;
  
  	if (log->log_transid == 1) {
  		/* insert root item on the first sync */
  		ret = btrfs_insert_root(trans, fs_info->log_root_tree,
  				&log->root_key, root_item);
  	} else {
  		ret = btrfs_update_root(trans, fs_info->log_root_tree,
  				&log->root_key, root_item);
  	}
  	return ret;
  }
  
  static void wait_log_commit(struct btrfs_root *root, int transid)
  {
  	DEFINE_WAIT(wait);
  	int index = transid % 2;
  
  	/*
  	 * we only allow two pending log transactions at a time,
  	 * so we know that if ours is more than 2 older than the
  	 * current transaction, we're done
  	 */
  	for (;;) {
  		prepare_to_wait(&root->log_commit_wait[index],
  				&wait, TASK_UNINTERRUPTIBLE);
  
  		if (!(root->log_transid_committed < transid &&
  		      atomic_read(&root->log_commit[index])))
  			break;
  
  		mutex_unlock(&root->log_mutex);
  		schedule();
  		mutex_lock(&root->log_mutex);
  	}
  	finish_wait(&root->log_commit_wait[index], &wait);
  }
  
  static void wait_for_writer(struct btrfs_root *root)
  {
  	DEFINE_WAIT(wait);
  
  	for (;;) {
  		prepare_to_wait(&root->log_writer_wait, &wait,
  				TASK_UNINTERRUPTIBLE);
  		if (!atomic_read(&root->log_writers))
  			break;
  
  		mutex_unlock(&root->log_mutex);
  		schedule();
  		mutex_lock(&root->log_mutex);
  	}
  	finish_wait(&root->log_writer_wait, &wait);
  }
  
  static inline void btrfs_remove_log_ctx(struct btrfs_root *root,
  					struct btrfs_log_ctx *ctx)
  {
  	if (!ctx)
  		return;
  
  	mutex_lock(&root->log_mutex);
  	list_del_init(&ctx->list);
  	mutex_unlock(&root->log_mutex);
  }
  
  /* 
   * Invoked in log mutex context, or be sure there is no other task which
   * can access the list.
   */
  static inline void btrfs_remove_all_log_ctxs(struct btrfs_root *root,
  					     int index, int error)
  {
  	struct btrfs_log_ctx *ctx;
  	struct btrfs_log_ctx *safe;
  
  	list_for_each_entry_safe(ctx, safe, &root->log_ctxs[index], list) {
  		list_del_init(&ctx->list);
  		ctx->log_ret = error;
  	}
  }
  
  /*
   * btrfs_sync_log does sends a given tree log down to the disk and
   * updates the super blocks to record it.  When this call is done,
   * you know that any inodes previously logged are safely on disk only
   * if it returns 0.
   *
   * Any other return value means you need to call btrfs_commit_transaction.
   * Some of the edge cases for fsyncing directories that have had unlinks
   * or renames done in the past mean that sometimes the only safe
   * fsync is to commit the whole FS.  When btrfs_sync_log returns -EAGAIN,
   * that has happened.
   */
  int btrfs_sync_log(struct btrfs_trans_handle *trans,
  		   struct btrfs_root *root, struct btrfs_log_ctx *ctx)
  {
  	int index1;
  	int index2;
  	int mark;
  	int ret;
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	struct btrfs_root *log = root->log_root;
  	struct btrfs_root *log_root_tree = fs_info->log_root_tree;
  	struct btrfs_root_item new_root_item;
  	int log_transid = 0;
  	struct btrfs_log_ctx root_log_ctx;
  	struct blk_plug plug;
  	u64 log_root_start;
  	u64 log_root_level;
  
  	mutex_lock(&root->log_mutex);
  	log_transid = ctx->log_transid;
  	if (root->log_transid_committed >= log_transid) {
  		mutex_unlock(&root->log_mutex);
  		return ctx->log_ret;
  	}
  
  	index1 = log_transid % 2;
  	if (atomic_read(&root->log_commit[index1])) {
  		wait_log_commit(root, log_transid);
  		mutex_unlock(&root->log_mutex);
  		return ctx->log_ret;
  	}
  	ASSERT(log_transid == root->log_transid);
  	atomic_set(&root->log_commit[index1], 1);
  
  	/* wait for previous tree log sync to complete */
  	if (atomic_read(&root->log_commit[(index1 + 1) % 2]))
  		wait_log_commit(root, log_transid - 1);
  
  	while (1) {
  		int batch = atomic_read(&root->log_batch);
  		/* when we're on an ssd, just kick the log commit out */
  		if (!btrfs_test_opt(fs_info, SSD) &&
  		    test_bit(BTRFS_ROOT_MULTI_LOG_TASKS, &root->state)) {
  			mutex_unlock(&root->log_mutex);
  			schedule_timeout_uninterruptible(1);
  			mutex_lock(&root->log_mutex);
  		}
  		wait_for_writer(root);
  		if (batch == atomic_read(&root->log_batch))
  			break;
  	}
  
  	/* bail out if we need to do a full commit */
  	if (btrfs_need_log_full_commit(trans)) {
  		ret = -EAGAIN;
  		mutex_unlock(&root->log_mutex);
  		goto out;
  	}
  
  	if (log_transid % 2 == 0)
  		mark = EXTENT_DIRTY;
  	else
  		mark = EXTENT_NEW;
  
  	/* we start IO on  all the marked extents here, but we don't actually
  	 * wait for them until later.
  	 */
  	blk_start_plug(&plug);
  	ret = btrfs_write_marked_extents(fs_info, &log->dirty_log_pages, mark);
  	/*
  	 * -EAGAIN happens when someone, e.g., a concurrent transaction
  	 *  commit, writes a dirty extent in this tree-log commit. This
  	 *  concurrent write will create a hole writing out the extents,
  	 *  and we cannot proceed on a zoned filesystem, requiring
  	 *  sequential writing. While we can bail out to a full commit
  	 *  here, but we can continue hoping the concurrent writing fills
  	 *  the hole.
  	 */
  	if (ret == -EAGAIN && btrfs_is_zoned(fs_info))
  		ret = 0;
  	if (ret) {
  		blk_finish_plug(&plug);
  		btrfs_abort_transaction(trans, ret);
  		btrfs_set_log_full_commit(trans);
  		mutex_unlock(&root->log_mutex);
  		goto out;
  	}
  
  	/*
  	 * We _must_ update under the root->log_mutex in order to make sure we
  	 * have a consistent view of the log root we are trying to commit at
  	 * this moment.
  	 *
  	 * We _must_ copy this into a local copy, because we are not holding the
  	 * log_root_tree->log_mutex yet.  This is important because when we
  	 * commit the log_root_tree we must have a consistent view of the
  	 * log_root_tree when we update the super block to point at the
  	 * log_root_tree bytenr.  If we update the log_root_tree here we'll race
  	 * with the commit and possibly point at the new block which we may not
  	 * have written out.
  	 */
  	btrfs_set_root_node(&log->root_item, log->node);
  	memcpy(&new_root_item, &log->root_item, sizeof(new_root_item));
  
  	root->log_transid++;
  	log->log_transid = root->log_transid;
  	root->log_start_pid = 0;
  	/*
  	 * IO has been started, blocks of the log tree have WRITTEN flag set
  	 * in their headers. new modifications of the log will be written to
  	 * new positions. so it's safe to allow log writers to go in.
  	 */
  	mutex_unlock(&root->log_mutex);
  
  	if (btrfs_is_zoned(fs_info)) {
  		mutex_lock(&fs_info->tree_root->log_mutex);
  		if (!log_root_tree->node) {
  			ret = btrfs_alloc_log_tree_node(trans, log_root_tree);
  			if (ret) {
  				mutex_unlock(&fs_info->tree_root->log_mutex);
  				goto out;
  			}
  		}
  		mutex_unlock(&fs_info->tree_root->log_mutex);
  	}
  
  	btrfs_init_log_ctx(&root_log_ctx, NULL);
  
  	mutex_lock(&log_root_tree->log_mutex);
  
  	index2 = log_root_tree->log_transid % 2;
  	list_add_tail(&root_log_ctx.list, &log_root_tree->log_ctxs[index2]);
  	root_log_ctx.log_transid = log_root_tree->log_transid;
  
  	/*
  	 * Now we are safe to update the log_root_tree because we're under the
  	 * log_mutex, and we're a current writer so we're holding the commit
  	 * open until we drop the log_mutex.
  	 */
  	ret = update_log_root(trans, log, &new_root_item);
  	if (ret) {
  		if (!list_empty(&root_log_ctx.list))
  			list_del_init(&root_log_ctx.list);
  
  		blk_finish_plug(&plug);
  		btrfs_set_log_full_commit(trans);
  
  		if (ret != -ENOSPC) {
  			btrfs_abort_transaction(trans, ret);
  			mutex_unlock(&log_root_tree->log_mutex);
  			goto out;
  		}
  		btrfs_wait_tree_log_extents(log, mark);
  		mutex_unlock(&log_root_tree->log_mutex);
  		ret = -EAGAIN;
  		goto out;
  	}
  
  	if (log_root_tree->log_transid_committed >= root_log_ctx.log_transid) {
  		blk_finish_plug(&plug);
  		list_del_init(&root_log_ctx.list);
  		mutex_unlock(&log_root_tree->log_mutex);
  		ret = root_log_ctx.log_ret;
  		goto out;
  	}
  
  	index2 = root_log_ctx.log_transid % 2;
  	if (atomic_read(&log_root_tree->log_commit[index2])) {
  		blk_finish_plug(&plug);
  		ret = btrfs_wait_tree_log_extents(log, mark);
  		wait_log_commit(log_root_tree,
  				root_log_ctx.log_transid);
  		mutex_unlock(&log_root_tree->log_mutex);
  		if (!ret)
  			ret = root_log_ctx.log_ret;
  		goto out;
  	}
  	ASSERT(root_log_ctx.log_transid == log_root_tree->log_transid);
  	atomic_set(&log_root_tree->log_commit[index2], 1);
  
  	if (atomic_read(&log_root_tree->log_commit[(index2 + 1) % 2])) {
  		wait_log_commit(log_root_tree,
  				root_log_ctx.log_transid - 1);
  	}
  
  	/*
  	 * now that we've moved on to the tree of log tree roots,
  	 * check the full commit flag again
  	 */
  	if (btrfs_need_log_full_commit(trans)) {
  		blk_finish_plug(&plug);
  		btrfs_wait_tree_log_extents(log, mark);
  		mutex_unlock(&log_root_tree->log_mutex);
  		ret = -EAGAIN;
  		goto out_wake_log_root;
  	}
  
  	ret = btrfs_write_marked_extents(fs_info,
  					 &log_root_tree->dirty_log_pages,
  					 EXTENT_DIRTY | EXTENT_NEW);
  	blk_finish_plug(&plug);
  	/*
  	 * As described above, -EAGAIN indicates a hole in the extents. We
  	 * cannot wait for these write outs since the waiting cause a
  	 * deadlock. Bail out to the full commit instead.
  	 */
  	if (ret == -EAGAIN && btrfs_is_zoned(fs_info)) {
  		btrfs_set_log_full_commit(trans);
  		btrfs_wait_tree_log_extents(log, mark);
  		mutex_unlock(&log_root_tree->log_mutex);
  		goto out_wake_log_root;
  	} else if (ret) {
  		btrfs_set_log_full_commit(trans);
  		btrfs_abort_transaction(trans, ret);
  		mutex_unlock(&log_root_tree->log_mutex);
  		goto out_wake_log_root;
  	}
  	ret = btrfs_wait_tree_log_extents(log, mark);
  	if (!ret)
  		ret = btrfs_wait_tree_log_extents(log_root_tree,
  						  EXTENT_NEW | EXTENT_DIRTY);
  	if (ret) {
  		btrfs_set_log_full_commit(trans);
  		mutex_unlock(&log_root_tree->log_mutex);
  		goto out_wake_log_root;
  	}
  
  	log_root_start = log_root_tree->node->start;
  	log_root_level = btrfs_header_level(log_root_tree->node);
  	log_root_tree->log_transid++;
  	mutex_unlock(&log_root_tree->log_mutex);
  
  	/*
  	 * Here we are guaranteed that nobody is going to write the superblock
  	 * for the current transaction before us and that neither we do write
  	 * our superblock before the previous transaction finishes its commit
  	 * and writes its superblock, because:
  	 *
  	 * 1) We are holding a handle on the current transaction, so no body
  	 *    can commit it until we release the handle;
  	 *
  	 * 2) Before writing our superblock we acquire the tree_log_mutex, so
  	 *    if the previous transaction is still committing, and hasn't yet
  	 *    written its superblock, we wait for it to do it, because a
  	 *    transaction commit acquires the tree_log_mutex when the commit
  	 *    begins and releases it only after writing its superblock.
  	 */
  	mutex_lock(&fs_info->tree_log_mutex);
  
  	/*
  	 * The previous transaction writeout phase could have failed, and thus
  	 * marked the fs in an error state.  We must not commit here, as we
  	 * could have updated our generation in the super_for_commit and
  	 * writing the super here would result in transid mismatches.  If there
  	 * is an error here just bail.
  	 */
  	if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
  		ret = -EIO;
  		btrfs_set_log_full_commit(trans);
  		btrfs_abort_transaction(trans, ret);
  		mutex_unlock(&fs_info->tree_log_mutex);
  		goto out_wake_log_root;
  	}
  
  	btrfs_set_super_log_root(fs_info->super_for_commit, log_root_start);
  	btrfs_set_super_log_root_level(fs_info->super_for_commit, log_root_level);
  	ret = write_all_supers(fs_info, 1);
  	mutex_unlock(&fs_info->tree_log_mutex);
  	if (ret) {
  		btrfs_set_log_full_commit(trans);
  		btrfs_abort_transaction(trans, ret);
  		goto out_wake_log_root;
  	}
  
  	/*
  	 * We know there can only be one task here, since we have not yet set
  	 * root->log_commit[index1] to 0 and any task attempting to sync the
  	 * log must wait for the previous log transaction to commit if it's
  	 * still in progress or wait for the current log transaction commit if
  	 * someone else already started it. We use <= and not < because the
  	 * first log transaction has an ID of 0.
  	 */
  	ASSERT(root->last_log_commit <= log_transid);
  	root->last_log_commit = log_transid;
  
  out_wake_log_root:
  	mutex_lock(&log_root_tree->log_mutex);
  	btrfs_remove_all_log_ctxs(log_root_tree, index2, ret);
  
  	log_root_tree->log_transid_committed++;
  	atomic_set(&log_root_tree->log_commit[index2], 0);
  	mutex_unlock(&log_root_tree->log_mutex);
  
  	/*
  	 * The barrier before waitqueue_active (in cond_wake_up) is needed so
  	 * all the updates above are seen by the woken threads. It might not be
  	 * necessary, but proving that seems to be hard.
  	 */
  	cond_wake_up(&log_root_tree->log_commit_wait[index2]);
  out:
  	mutex_lock(&root->log_mutex);
  	btrfs_remove_all_log_ctxs(root, index1, ret);
  	root->log_transid_committed++;
  	atomic_set(&root->log_commit[index1], 0);
  	mutex_unlock(&root->log_mutex);
  
  	/*
  	 * The barrier before waitqueue_active (in cond_wake_up) is needed so
  	 * all the updates above are seen by the woken threads. It might not be
  	 * necessary, but proving that seems to be hard.
  	 */
  	cond_wake_up(&root->log_commit_wait[index1]);
  	return ret;
  }
  
  static void free_log_tree(struct btrfs_trans_handle *trans,
  			  struct btrfs_root *log)
  {
  	int ret;
  	struct walk_control wc = {
  		.free = 1,
  		.process_func = process_one_buffer
  	};
  
  	if (log->node) {
  		ret = walk_log_tree(trans, log, &wc);
  		if (ret) {
  			if (trans)
  				btrfs_abort_transaction(trans, ret);
  			else
  				btrfs_handle_fs_error(log->fs_info, ret, NULL);
  		}
  	}
  
  	clear_extent_bits(&log->dirty_log_pages, 0, (u64)-1,
  			  EXTENT_DIRTY | EXTENT_NEW | EXTENT_NEED_WAIT);
  	extent_io_tree_release(&log->log_csum_range);
  
  	btrfs_put_root(log);
  }
  
  /*
   * free all the extents used by the tree log.  This should be called
   * at commit time of the full transaction
   */
  int btrfs_free_log(struct btrfs_trans_handle *trans, struct btrfs_root *root)
  {
  	if (root->log_root) {
  		free_log_tree(trans, root->log_root);
  		root->log_root = NULL;
  		clear_bit(BTRFS_ROOT_HAS_LOG_TREE, &root->state);
  	}
  	return 0;
  }
  
  int btrfs_free_log_root_tree(struct btrfs_trans_handle *trans,
  			     struct btrfs_fs_info *fs_info)
  {
  	if (fs_info->log_root_tree) {
  		free_log_tree(trans, fs_info->log_root_tree);
  		fs_info->log_root_tree = NULL;
  		clear_bit(BTRFS_ROOT_HAS_LOG_TREE, &fs_info->tree_root->state);
  	}
  	return 0;
  }
  
  /*
   * Check if an inode was logged in the current transaction. This may often
   * return some false positives, because logged_trans is an in memory only field,
   * not persisted anywhere. This is meant to be used in contexts where a false
   * positive has no functional consequences.
   */
  static bool inode_logged(struct btrfs_trans_handle *trans,
  			 struct btrfs_inode *inode)
  {
  	if (inode->logged_trans == trans->transid)
  		return true;
  
  	/*
  	 * The inode's logged_trans is always 0 when we load it (because it is
  	 * not persisted in the inode item or elsewhere). So if it is 0, the
  	 * inode was last modified in the current transaction then the inode may
  	 * have been logged before in the current transaction, then evicted and
  	 * loaded again in the current transaction - or may have never been logged
  	 * in the current transaction, but since we can not be sure, we have to
  	 * assume it was, otherwise our callers can leave an inconsistent log.
  	 */
  	if (inode->logged_trans == 0 &&
  	    inode->last_trans == trans->transid &&
  	    !test_bit(BTRFS_FS_LOG_RECOVERING, &trans->fs_info->flags))
  		return true;
  
  	return false;
  }
  
  /*
   * If both a file and directory are logged, and unlinks or renames are
   * mixed in, we have a few interesting corners:
   *
   * create file X in dir Y
   * link file X to X.link in dir Y
   * fsync file X
   * unlink file X but leave X.link
   * fsync dir Y
   *
   * After a crash we would expect only X.link to exist.  But file X
   * didn't get fsync'd again so the log has back refs for X and X.link.
   *
   * We solve this by removing directory entries and inode backrefs from the
   * log when a file that was logged in the current transaction is
   * unlinked.  Any later fsync will include the updated log entries, and
   * we'll be able to reconstruct the proper directory items from backrefs.
   *
   * This optimizations allows us to avoid relogging the entire inode
   * or the entire directory.
   */
  int btrfs_del_dir_entries_in_log(struct btrfs_trans_handle *trans,
  				 struct btrfs_root *root,
  				 const char *name, int name_len,
  				 struct btrfs_inode *dir, u64 index)
  {
  	struct btrfs_root *log;
  	struct btrfs_dir_item *di;
  	struct btrfs_path *path;
  	int ret;
  	int err = 0;
  	u64 dir_ino = btrfs_ino(dir);
  
  	if (!inode_logged(trans, dir))
  		return 0;
  
  	ret = join_running_log_trans(root);
  	if (ret)
  		return 0;
  
  	mutex_lock(&dir->log_mutex);
  
  	log = root->log_root;
  	path = btrfs_alloc_path();
  	if (!path) {
  		err = -ENOMEM;
  		goto out_unlock;
  	}
  
  	di = btrfs_lookup_dir_item(trans, log, path, dir_ino,
  				   name, name_len, -1);
  	if (IS_ERR(di)) {
  		err = PTR_ERR(di);
  		goto fail;
  	}
  	if (di) {
  		ret = btrfs_delete_one_dir_name(trans, log, path, di);
  		if (ret) {
  			err = ret;
  			goto fail;
  		}
  	}
  	btrfs_release_path(path);
  	di = btrfs_lookup_dir_index_item(trans, log, path, dir_ino,
  					 index, name, name_len, -1);
  	if (IS_ERR(di)) {
  		err = PTR_ERR(di);
  		goto fail;
  	}
  	if (di) {
  		ret = btrfs_delete_one_dir_name(trans, log, path, di);
  		if (ret) {
  			err = ret;
  			goto fail;
  		}
  	}
  
  	/*
  	 * We do not need to update the size field of the directory's inode item
  	 * because on log replay we update the field to reflect all existing
  	 * entries in the directory (see overwrite_item()).
  	 */
  fail:
  	btrfs_free_path(path);
  out_unlock:
  	mutex_unlock(&dir->log_mutex);
  	if (err == -ENOSPC) {
  		btrfs_set_log_full_commit(trans);
  		err = 0;
  	} else if (err < 0) {
  		btrfs_abort_transaction(trans, err);
  	}
  
  	btrfs_end_log_trans(root);
  
  	return err;
  }
  
  /* see comments for btrfs_del_dir_entries_in_log */
  int btrfs_del_inode_ref_in_log(struct btrfs_trans_handle *trans,
  			       struct btrfs_root *root,
  			       const char *name, int name_len,
  			       struct btrfs_inode *inode, u64 dirid)
  {
  	struct btrfs_root *log;
  	u64 index;
  	int ret;
  
  	if (!inode_logged(trans, inode))
  		return 0;
  
  	ret = join_running_log_trans(root);
  	if (ret)
  		return 0;
  	log = root->log_root;
  	mutex_lock(&inode->log_mutex);
  
  	ret = btrfs_del_inode_ref(trans, log, name, name_len, btrfs_ino(inode),
  				  dirid, &index);
  	mutex_unlock(&inode->log_mutex);
  	if (ret == -ENOSPC) {
  		btrfs_set_log_full_commit(trans);
  		ret = 0;
  	} else if (ret < 0 && ret != -ENOENT)
  		btrfs_abort_transaction(trans, ret);
  	btrfs_end_log_trans(root);
  
  	return ret;
  }
  
  /*
   * creates a range item in the log for 'dirid'.  first_offset and
   * last_offset tell us which parts of the key space the log should
   * be considered authoritative for.
   */
  static noinline int insert_dir_log_key(struct btrfs_trans_handle *trans,
  				       struct btrfs_root *log,
  				       struct btrfs_path *path,
  				       int key_type, u64 dirid,
  				       u64 first_offset, u64 last_offset)
  {
  	int ret;
  	struct btrfs_key key;
  	struct btrfs_dir_log_item *item;
  
  	key.objectid = dirid;
  	key.offset = first_offset;
  	if (key_type == BTRFS_DIR_ITEM_KEY)
  		key.type = BTRFS_DIR_LOG_ITEM_KEY;
  	else
  		key.type = BTRFS_DIR_LOG_INDEX_KEY;
  	ret = btrfs_insert_empty_item(trans, log, path, &key, sizeof(*item));
  	if (ret)
  		return ret;
  
  	item = btrfs_item_ptr(path->nodes[0], path->slots[0],
  			      struct btrfs_dir_log_item);
  	btrfs_set_dir_log_end(path->nodes[0], item, last_offset);
  	btrfs_mark_buffer_dirty(path->nodes[0]);
  	btrfs_release_path(path);
  	return 0;
  }
  
  /*
   * log all the items included in the current transaction for a given
   * directory.  This also creates the range items in the log tree required
   * to replay anything deleted before the fsync
   */
  static noinline int log_dir_items(struct btrfs_trans_handle *trans,
  			  struct btrfs_root *root, struct btrfs_inode *inode,
  			  struct btrfs_path *path,
  			  struct btrfs_path *dst_path, int key_type,
  			  struct btrfs_log_ctx *ctx,
  			  u64 min_offset, u64 *last_offset_ret)
  {
  	struct btrfs_key min_key;
  	struct btrfs_root *log = root->log_root;
  	struct extent_buffer *src;
  	int err = 0;
  	int ret;
  	int i;
  	int nritems;
  	u64 first_offset = min_offset;
  	u64 last_offset = (u64)-1;
  	u64 ino = btrfs_ino(inode);
  
  	log = root->log_root;
  
  	min_key.objectid = ino;
  	min_key.type = key_type;
  	min_key.offset = min_offset;
  
  	ret = btrfs_search_forward(root, &min_key, path, trans->transid);
  
  	/*
  	 * we didn't find anything from this transaction, see if there
  	 * is anything at all
  	 */
  	if (ret != 0 || min_key.objectid != ino || min_key.type != key_type) {
  		min_key.objectid = ino;
  		min_key.type = key_type;
  		min_key.offset = (u64)-1;
  		btrfs_release_path(path);
  		ret = btrfs_search_slot(NULL, root, &min_key, path, 0, 0);
  		if (ret < 0) {
  			btrfs_release_path(path);
  			return ret;
  		}
  		ret = btrfs_previous_item(root, path, ino, key_type);
  
  		/* if ret == 0 there are items for this type,
  		 * create a range to tell us the last key of this type.
  		 * otherwise, there are no items in this directory after
  		 * *min_offset, and we create a range to indicate that.
  		 */
  		if (ret == 0) {
  			struct btrfs_key tmp;
  			btrfs_item_key_to_cpu(path->nodes[0], &tmp,
  					      path->slots[0]);
  			if (key_type == tmp.type)
  				first_offset = max(min_offset, tmp.offset) + 1;
  		}
  		goto done;
  	}
  
  	/* go backward to find any previous key */
  	ret = btrfs_previous_item(root, path, ino, key_type);
  	if (ret == 0) {
  		struct btrfs_key tmp;
  		btrfs_item_key_to_cpu(path->nodes[0], &tmp, path->slots[0]);
  		if (key_type == tmp.type) {
  			first_offset = tmp.offset;
  			ret = overwrite_item(trans, log, dst_path,
  					     path->nodes[0], path->slots[0],
  					     &tmp);
  			if (ret) {
  				err = ret;
  				goto done;
  			}
  		}
  	}
  	btrfs_release_path(path);
  
  	/*
  	 * Find the first key from this transaction again.  See the note for
  	 * log_new_dir_dentries, if we're logging a directory recursively we
  	 * won't be holding its i_mutex, which means we can modify the directory
  	 * while we're logging it.  If we remove an entry between our first
  	 * search and this search we'll not find the key again and can just
  	 * bail.
  	 */
  search:
  	ret = btrfs_search_slot(NULL, root, &min_key, path, 0, 0);
  	if (ret != 0)
  		goto done;
  
  	/*
  	 * we have a block from this transaction, log every item in it
  	 * from our directory
  	 */
  	while (1) {
  		struct btrfs_key tmp;
  		src = path->nodes[0];
  		nritems = btrfs_header_nritems(src);
  		for (i = path->slots[0]; i < nritems; i++) {
  			struct btrfs_dir_item *di;
  
  			btrfs_item_key_to_cpu(src, &min_key, i);
  
  			if (min_key.objectid != ino || min_key.type != key_type)
  				goto done;
  
  			if (need_resched()) {
  				btrfs_release_path(path);
  				cond_resched();
  				goto search;
  			}
  
  			ret = overwrite_item(trans, log, dst_path, src, i,
  					     &min_key);
  			if (ret) {
  				err = ret;
  				goto done;
  			}
  
  			/*
  			 * We must make sure that when we log a directory entry,
  			 * the corresponding inode, after log replay, has a
  			 * matching link count. For example:
  			 *
  			 * touch foo
  			 * mkdir mydir
  			 * sync
  			 * ln foo mydir/bar
  			 * xfs_io -c "fsync" mydir
  			 * <crash>
  			 * <mount fs and log replay>
  			 *
  			 * Would result in a fsync log that when replayed, our
  			 * file inode would have a link count of 1, but we get
  			 * two directory entries pointing to the same inode.
  			 * After removing one of the names, it would not be
  			 * possible to remove the other name, which resulted
  			 * always in stale file handle errors, and would not
  			 * be possible to rmdir the parent directory, since
  			 * its i_size could never decrement to the value
  			 * BTRFS_EMPTY_DIR_SIZE, resulting in -ENOTEMPTY errors.
  			 */
  			di = btrfs_item_ptr(src, i, struct btrfs_dir_item);
  			btrfs_dir_item_key_to_cpu(src, di, &tmp);
  			if (ctx &&
  			    (btrfs_dir_transid(src, di) == trans->transid ||
  			     btrfs_dir_type(src, di) == BTRFS_FT_DIR) &&
  			    tmp.type != BTRFS_ROOT_ITEM_KEY)
  				ctx->log_new_dentries = true;
  		}
  		path->slots[0] = nritems;
  
  		/*
  		 * look ahead to the next item and see if it is also
  		 * from this directory and from this transaction
  		 */
  		ret = btrfs_next_leaf(root, path);
  		if (ret) {
  			if (ret == 1)
  				last_offset = (u64)-1;
  			else
  				err = ret;
  			goto done;
  		}
  		btrfs_item_key_to_cpu(path->nodes[0], &tmp, path->slots[0]);
  		if (tmp.objectid != ino || tmp.type != key_type) {
  			last_offset = (u64)-1;
  			goto done;
  		}
  		if (btrfs_header_generation(path->nodes[0]) != trans->transid) {
  			ret = overwrite_item(trans, log, dst_path,
  					     path->nodes[0], path->slots[0],
  					     &tmp);
  			if (ret)
  				err = ret;
  			else
  				last_offset = tmp.offset;
  			goto done;
  		}
  	}
  done:
  	btrfs_release_path(path);
  	btrfs_release_path(dst_path);
  
  	if (err == 0) {
  		*last_offset_ret = last_offset;
  		/*
  		 * insert the log range keys to indicate where the log
  		 * is valid
  		 */
  		ret = insert_dir_log_key(trans, log, path, key_type,
  					 ino, first_offset, last_offset);
  		if (ret)
  			err = ret;
  	}
  	return err;
  }
  
  /*
   * logging directories is very similar to logging inodes, We find all the items
   * from the current transaction and write them to the log.
   *
   * The recovery code scans the directory in the subvolume, and if it finds a
   * key in the range logged that is not present in the log tree, then it means
   * that dir entry was unlinked during the transaction.
   *
   * In order for that scan to work, we must include one key smaller than
   * the smallest logged by this transaction and one key larger than the largest
   * key logged by this transaction.
   */
  static noinline int log_directory_changes(struct btrfs_trans_handle *trans,
  			  struct btrfs_root *root, struct btrfs_inode *inode,
  			  struct btrfs_path *path,
  			  struct btrfs_path *dst_path,
  			  struct btrfs_log_ctx *ctx)
  {
  	u64 min_key;
  	u64 max_key;
  	int ret;
  	int key_type = BTRFS_DIR_ITEM_KEY;
  
  again:
  	min_key = 0;
  	max_key = 0;
  	while (1) {
  		ret = log_dir_items(trans, root, inode, path, dst_path, key_type,
  				ctx, min_key, &max_key);
  		if (ret)
  			return ret;
  		if (max_key == (u64)-1)
  			break;
  		min_key = max_key + 1;
  	}
  
  	if (key_type == BTRFS_DIR_ITEM_KEY) {
  		key_type = BTRFS_DIR_INDEX_KEY;
  		goto again;
  	}
  	return 0;
  }
  
  /*
   * a helper function to drop items from the log before we relog an
   * inode.  max_key_type indicates the highest item type to remove.
   * This cannot be run for file data extents because it does not
   * free the extents they point to.
   */
  static int drop_objectid_items(struct btrfs_trans_handle *trans,
  				  struct btrfs_root *log,
  				  struct btrfs_path *path,
  				  u64 objectid, int max_key_type)
  {
  	int ret;
  	struct btrfs_key key;
  	struct btrfs_key found_key;
  	int start_slot;
  
  	key.objectid = objectid;
  	key.type = max_key_type;
  	key.offset = (u64)-1;
  
  	while (1) {
  		ret = btrfs_search_slot(trans, log, &key, path, -1, 1);
  		BUG_ON(ret == 0); /* Logic error */
  		if (ret < 0)
  			break;
  
  		if (path->slots[0] == 0)
  			break;
  
  		path->slots[0]--;
  		btrfs_item_key_to_cpu(path->nodes[0], &found_key,
  				      path->slots[0]);
  
  		if (found_key.objectid != objectid)
  			break;
  
  		found_key.offset = 0;
  		found_key.type = 0;
  		ret = btrfs_bin_search(path->nodes[0], &found_key, &start_slot);
  		if (ret < 0)
  			break;
  
  		ret = btrfs_del_items(trans, log, path, start_slot,
  				      path->slots[0] - start_slot + 1);
  		/*
  		 * If start slot isn't 0 then we don't need to re-search, we've
  		 * found the last guy with the objectid in this tree.
  		 */
  		if (ret || start_slot != 0)
  			break;
  		btrfs_release_path(path);
  	}
  	btrfs_release_path(path);
  	if (ret > 0)
  		ret = 0;
  	return ret;
  }
  
  static void fill_inode_item(struct btrfs_trans_handle *trans,
  			    struct extent_buffer *leaf,
  			    struct btrfs_inode_item *item,
  			    struct inode *inode, int log_inode_only,
  			    u64 logged_isize)
  {
  	struct btrfs_map_token token;
  	u64 flags;
  
  	btrfs_init_map_token(&token, leaf);
  
  	if (log_inode_only) {
  		/* set the generation to zero so the recover code
  		 * can tell the difference between an logging
  		 * just to say 'this inode exists' and a logging
  		 * to say 'update this inode with these values'
  		 */
  		btrfs_set_token_inode_generation(&token, item, 0);
  		btrfs_set_token_inode_size(&token, item, logged_isize);
  	} else {
  		btrfs_set_token_inode_generation(&token, item,
  						 BTRFS_I(inode)->generation);
  		btrfs_set_token_inode_size(&token, item, inode->i_size);
  	}
  
  	btrfs_set_token_inode_uid(&token, item, i_uid_read(inode));
  	btrfs_set_token_inode_gid(&token, item, i_gid_read(inode));
  	btrfs_set_token_inode_mode(&token, item, inode->i_mode);
  	btrfs_set_token_inode_nlink(&token, item, inode->i_nlink);
  
  	btrfs_set_token_timespec_sec(&token, &item->atime,
  				     inode->i_atime.tv_sec);
  	btrfs_set_token_timespec_nsec(&token, &item->atime,
  				      inode->i_atime.tv_nsec);
  
  	btrfs_set_token_timespec_sec(&token, &item->mtime,
  				     inode->i_mtime.tv_sec);
  	btrfs_set_token_timespec_nsec(&token, &item->mtime,
  				      inode->i_mtime.tv_nsec);
  
  	btrfs_set_token_timespec_sec(&token, &item->ctime,
  				     inode->i_ctime.tv_sec);
  	btrfs_set_token_timespec_nsec(&token, &item->ctime,
  				      inode->i_ctime.tv_nsec);
  
  	/*
  	 * We do not need to set the nbytes field, in fact during a fast fsync
  	 * its value may not even be correct, since a fast fsync does not wait
  	 * for ordered extent completion, which is where we update nbytes, it
  	 * only waits for writeback to complete. During log replay as we find
  	 * file extent items and replay them, we adjust the nbytes field of the
  	 * inode item in subvolume tree as needed (see overwrite_item()).
  	 */
  
  	btrfs_set_token_inode_sequence(&token, item, inode_peek_iversion(inode));
  	btrfs_set_token_inode_transid(&token, item, trans->transid);
  	btrfs_set_token_inode_rdev(&token, item, inode->i_rdev);
  	flags = btrfs_inode_combine_flags(BTRFS_I(inode)->flags,
  					  BTRFS_I(inode)->ro_flags);
  	btrfs_set_token_inode_flags(&token, item, flags);
  	btrfs_set_token_inode_block_group(&token, item, 0);
  }
  
  static int log_inode_item(struct btrfs_trans_handle *trans,
  			  struct btrfs_root *log, struct btrfs_path *path,
  			  struct btrfs_inode *inode, bool inode_item_dropped)
  {
  	struct btrfs_inode_item *inode_item;
  	int ret;
  
  	/*
  	 * If we are doing a fast fsync and the inode was logged before in the
  	 * current transaction, then we know the inode was previously logged and
  	 * it exists in the log tree. For performance reasons, in this case use
  	 * btrfs_search_slot() directly with ins_len set to 0 so that we never
  	 * attempt a write lock on the leaf's parent, which adds unnecessary lock
  	 * contention in case there are concurrent fsyncs for other inodes of the
  	 * same subvolume. Using btrfs_insert_empty_item() when the inode item
  	 * already exists can also result in unnecessarily splitting a leaf.
  	 */
  	if (!inode_item_dropped && inode->logged_trans == trans->transid) {
  		ret = btrfs_search_slot(trans, log, &inode->location, path, 0, 1);
  		ASSERT(ret <= 0);
  		if (ret > 0)
  			ret = -ENOENT;
  	} else {
  		/*
  		 * This means it is the first fsync in the current transaction,
  		 * so the inode item is not in the log and we need to insert it.
  		 * We can never get -EEXIST because we are only called for a fast
  		 * fsync and in case an inode eviction happens after the inode was
  		 * logged before in the current transaction, when we load again
  		 * the inode, we set BTRFS_INODE_NEEDS_FULL_SYNC on its runtime
  		 * flags and set ->logged_trans to 0.
  		 */
  		ret = btrfs_insert_empty_item(trans, log, path, &inode->location,
  					      sizeof(*inode_item));
  		ASSERT(ret != -EEXIST);
  	}
  	if (ret)
  		return ret;
  	inode_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
  				    struct btrfs_inode_item);
  	fill_inode_item(trans, path->nodes[0], inode_item, &inode->vfs_inode,
  			0, 0);
  	btrfs_release_path(path);
  	return 0;
  }
  
  static int log_csums(struct btrfs_trans_handle *trans,
  		     struct btrfs_inode *inode,
  		     struct btrfs_root *log_root,
  		     struct btrfs_ordered_sum *sums)
  {
  	const u64 lock_end = sums->bytenr + sums->len - 1;
  	struct extent_state *cached_state = NULL;
  	int ret;
  
  	/*
  	 * If this inode was not used for reflink operations in the current
  	 * transaction with new extents, then do the fast path, no need to
  	 * worry about logging checksum items with overlapping ranges.
  	 */
  	if (inode->last_reflink_trans < trans->transid)
  		return btrfs_csum_file_blocks(trans, log_root, sums);
  
  	/*
  	 * Serialize logging for checksums. This is to avoid racing with the
  	 * same checksum being logged by another task that is logging another
  	 * file which happens to refer to the same extent as well. Such races
  	 * can leave checksum items in the log with overlapping ranges.
  	 */
  	ret = lock_extent_bits(&log_root->log_csum_range, sums->bytenr,
  			       lock_end, &cached_state);
  	if (ret)
  		return ret;
  	/*
  	 * Due to extent cloning, we might have logged a csum item that covers a
  	 * subrange of a cloned extent, and later we can end up logging a csum
  	 * item for a larger subrange of the same extent or the entire range.
  	 * This would leave csum items in the log tree that cover the same range
  	 * and break the searches for checksums in the log tree, resulting in
  	 * some checksums missing in the fs/subvolume tree. So just delete (or
  	 * trim and adjust) any existing csum items in the log for this range.
  	 */
  	ret = btrfs_del_csums(trans, log_root, sums->bytenr, sums->len);
  	if (!ret)
  		ret = btrfs_csum_file_blocks(trans, log_root, sums);
  
  	unlock_extent_cached(&log_root->log_csum_range, sums->bytenr, lock_end,
  			     &cached_state);
  
  	return ret;
  }
  
  static noinline int copy_items(struct btrfs_trans_handle *trans,
  			       struct btrfs_inode *inode,
  			       struct btrfs_path *dst_path,
  			       struct btrfs_path *src_path,
  			       int start_slot, int nr, int inode_only,
  			       u64 logged_isize)
  {
  	struct btrfs_fs_info *fs_info = trans->fs_info;
  	unsigned long src_offset;
  	unsigned long dst_offset;
  	struct btrfs_root *log = inode->root->log_root;
  	struct btrfs_file_extent_item *extent;
  	struct btrfs_inode_item *inode_item;
  	struct extent_buffer *src = src_path->nodes[0];
  	int ret;
  	struct btrfs_key *ins_keys;
  	u32 *ins_sizes;
  	char *ins_data;
  	int i;
  	struct list_head ordered_sums;
  	int skip_csum = inode->flags & BTRFS_INODE_NODATASUM;
  
  	INIT_LIST_HEAD(&ordered_sums);
  
  	ins_data = kmalloc(nr * sizeof(struct btrfs_key) +
  			   nr * sizeof(u32), GFP_NOFS);
  	if (!ins_data)
  		return -ENOMEM;
  
  	ins_sizes = (u32 *)ins_data;
  	ins_keys = (struct btrfs_key *)(ins_data + nr * sizeof(u32));
  
  	for (i = 0; i < nr; i++) {
  		ins_sizes[i] = btrfs_item_size_nr(src, i + start_slot);
  		btrfs_item_key_to_cpu(src, ins_keys + i, i + start_slot);
  	}
  	ret = btrfs_insert_empty_items(trans, log, dst_path,
  				       ins_keys, ins_sizes, nr);
  	if (ret) {
  		kfree(ins_data);
  		return ret;
  	}
  
  	for (i = 0; i < nr; i++, dst_path->slots[0]++) {
  		dst_offset = btrfs_item_ptr_offset(dst_path->nodes[0],
  						   dst_path->slots[0]);
  
  		src_offset = btrfs_item_ptr_offset(src, start_slot + i);
  
  		if (ins_keys[i].type == BTRFS_INODE_ITEM_KEY) {
  			inode_item = btrfs_item_ptr(dst_path->nodes[0],
  						    dst_path->slots[0],
  						    struct btrfs_inode_item);
  			fill_inode_item(trans, dst_path->nodes[0], inode_item,
  					&inode->vfs_inode,
  					inode_only == LOG_INODE_EXISTS,
  					logged_isize);
  		} else {
  			copy_extent_buffer(dst_path->nodes[0], src, dst_offset,
  					   src_offset, ins_sizes[i]);
  		}
  
  		/* take a reference on file data extents so that truncates
  		 * or deletes of this inode don't have to relog the inode
  		 * again
  		 */
  		if (ins_keys[i].type == BTRFS_EXTENT_DATA_KEY &&
  		    !skip_csum) {
  			int found_type;
  			extent = btrfs_item_ptr(src, start_slot + i,
  						struct btrfs_file_extent_item);
  
  			if (btrfs_file_extent_generation(src, extent) < trans->transid)
  				continue;
  
  			found_type = btrfs_file_extent_type(src, extent);
  			if (found_type == BTRFS_FILE_EXTENT_REG) {
  				u64 ds, dl, cs, cl;
  				ds = btrfs_file_extent_disk_bytenr(src,
  								extent);
  				/* ds == 0 is a hole */
  				if (ds == 0)
  					continue;
  
  				dl = btrfs_file_extent_disk_num_bytes(src,
  								extent);
  				cs = btrfs_file_extent_offset(src, extent);
  				cl = btrfs_file_extent_num_bytes(src,
  								extent);
  				if (btrfs_file_extent_compression(src,
  								  extent)) {
  					cs = 0;
  					cl = dl;
  				}
  
  				ret = btrfs_lookup_csums_range(
  						fs_info->csum_root,
  						ds + cs, ds + cs + cl - 1,
  						&ordered_sums, 0);
  				if (ret)
  					break;
  			}
  		}
  	}
  
  	btrfs_mark_buffer_dirty(dst_path->nodes[0]);
  	btrfs_release_path(dst_path);
  	kfree(ins_data);
  
  	/*
  	 * we have to do this after the loop above to avoid changing the
  	 * log tree while trying to change the log tree.
  	 */
  	while (!list_empty(&ordered_sums)) {
  		struct btrfs_ordered_sum *sums = list_entry(ordered_sums.next,
  						   struct btrfs_ordered_sum,
  						   list);
  		if (!ret)
  			ret = log_csums(trans, inode, log, sums);
  		list_del(&sums->list);
  		kfree(sums);
  	}
  
  	return ret;
  }
  
  static int extent_cmp(void *priv, const struct list_head *a,
  		      const struct list_head *b)
  {
  	const struct extent_map *em1, *em2;
  
  	em1 = list_entry(a, struct extent_map, list);
  	em2 = list_entry(b, struct extent_map, list);
  
  	if (em1->start < em2->start)
  		return -1;
  	else if (em1->start > em2->start)
  		return 1;
  	return 0;
  }
  
  static int log_extent_csums(struct btrfs_trans_handle *trans,
  			    struct btrfs_inode *inode,
  			    struct btrfs_root *log_root,
  			    const struct extent_map *em,
  			    struct btrfs_log_ctx *ctx)
  {
  	struct btrfs_ordered_extent *ordered;
  	u64 csum_offset;
  	u64 csum_len;
  	u64 mod_start = em->mod_start;
  	u64 mod_len = em->mod_len;
  	LIST_HEAD(ordered_sums);
  	int ret = 0;
  
  	if (inode->flags & BTRFS_INODE_NODATASUM ||
  	    test_bit(EXTENT_FLAG_PREALLOC, &em->flags) ||
  	    em->block_start == EXTENT_MAP_HOLE)
  		return 0;
  
  	list_for_each_entry(ordered, &ctx->ordered_extents, log_list) {
  		const u64 ordered_end = ordered->file_offset + ordered->num_bytes;
  		const u64 mod_end = mod_start + mod_len;
  		struct btrfs_ordered_sum *sums;
  
  		if (mod_len == 0)
  			break;
  
  		if (ordered_end <= mod_start)
  			continue;
  		if (mod_end <= ordered->file_offset)
  			break;
  
  		/*
  		 * We are going to copy all the csums on this ordered extent, so
  		 * go ahead and adjust mod_start and mod_len in case this ordered
  		 * extent has already been logged.
  		 */
  		if (ordered->file_offset > mod_start) {
  			if (ordered_end >= mod_end)
  				mod_len = ordered->file_offset - mod_start;
  			/*
  			 * If we have this case
  			 *
  			 * |--------- logged extent ---------|
  			 *       |----- ordered extent ----|
  			 *
  			 * Just don't mess with mod_start and mod_len, we'll
  			 * just end up logging more csums than we need and it
  			 * will be ok.
  			 */
  		} else {
  			if (ordered_end < mod_end) {
  				mod_len = mod_end - ordered_end;
  				mod_start = ordered_end;
  			} else {
  				mod_len = 0;
  			}
  		}
  
  		/*
  		 * To keep us from looping for the above case of an ordered
  		 * extent that falls inside of the logged extent.
  		 */
  		if (test_and_set_bit(BTRFS_ORDERED_LOGGED_CSUM, &ordered->flags))
  			continue;
  
  		list_for_each_entry(sums, &ordered->list, list) {
  			ret = log_csums(trans, inode, log_root, sums);
  			if (ret)
  				return ret;
  		}
  	}
  
  	/* We're done, found all csums in the ordered extents. */
  	if (mod_len == 0)
  		return 0;
  
  	/* If we're compressed we have to save the entire range of csums. */
  	if (em->compress_type) {
  		csum_offset = 0;
  		csum_len = max(em->block_len, em->orig_block_len);
  	} else {
  		csum_offset = mod_start - em->start;
  		csum_len = mod_len;
  	}
  
  	/* block start is already adjusted for the file extent offset. */
  	ret = btrfs_lookup_csums_range(trans->fs_info->csum_root,
  				       em->block_start + csum_offset,
  				       em->block_start + csum_offset +
  				       csum_len - 1, &ordered_sums, 0);
  	if (ret)
  		return ret;
  
  	while (!list_empty(&ordered_sums)) {
  		struct btrfs_ordered_sum *sums = list_entry(ordered_sums.next,
  						   struct btrfs_ordered_sum,
  						   list);
  		if (!ret)
  			ret = log_csums(trans, inode, log_root, sums);
  		list_del(&sums->list);
  		kfree(sums);
  	}
  
  	return ret;
  }
  
  static int log_one_extent(struct btrfs_trans_handle *trans,
  			  struct btrfs_inode *inode, struct btrfs_root *root,
  			  const struct extent_map *em,
  			  struct btrfs_path *path,
  			  struct btrfs_log_ctx *ctx)
  {
  	struct btrfs_drop_extents_args drop_args = { 0 };
  	struct btrfs_root *log = root->log_root;
  	struct btrfs_file_extent_item *fi;
  	struct extent_buffer *leaf;
  	struct btrfs_map_token token;
  	struct btrfs_key key;
  	u64 extent_offset = em->start - em->orig_start;
  	u64 block_len;
  	int ret;
  
  	ret = log_extent_csums(trans, inode, log, em, ctx);
  	if (ret)
  		return ret;
  
  	drop_args.path = path;
  	drop_args.start = em->start;
  	drop_args.end = em->start + em->len;
  	drop_args.replace_extent = true;
  	drop_args.extent_item_size = sizeof(*fi);
  	ret = btrfs_drop_extents(trans, log, inode, &drop_args);
  	if (ret)
  		return ret;
  
  	if (!drop_args.extent_inserted) {
  		key.objectid = btrfs_ino(inode);
  		key.type = BTRFS_EXTENT_DATA_KEY;
  		key.offset = em->start;
  
  		ret = btrfs_insert_empty_item(trans, log, path, &key,
  					      sizeof(*fi));
  		if (ret)
  			return ret;
  	}
  	leaf = path->nodes[0];
  	btrfs_init_map_token(&token, leaf);
  	fi = btrfs_item_ptr(leaf, path->slots[0],
  			    struct btrfs_file_extent_item);
  
  	btrfs_set_token_file_extent_generation(&token, fi, trans->transid);
  	if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
  		btrfs_set_token_file_extent_type(&token, fi,
  						 BTRFS_FILE_EXTENT_PREALLOC);
  	else
  		btrfs_set_token_file_extent_type(&token, fi,
  						 BTRFS_FILE_EXTENT_REG);
  
  	block_len = max(em->block_len, em->orig_block_len);
  	if (em->compress_type != BTRFS_COMPRESS_NONE) {
  		btrfs_set_token_file_extent_disk_bytenr(&token, fi,
  							em->block_start);
  		btrfs_set_token_file_extent_disk_num_bytes(&token, fi, block_len);
  	} else if (em->block_start < EXTENT_MAP_LAST_BYTE) {
  		btrfs_set_token_file_extent_disk_bytenr(&token, fi,
  							em->block_start -
  							extent_offset);
  		btrfs_set_token_file_extent_disk_num_bytes(&token, fi, block_len);
  	} else {
  		btrfs_set_token_file_extent_disk_bytenr(&token, fi, 0);
  		btrfs_set_token_file_extent_disk_num_bytes(&token, fi, 0);
  	}
  
  	btrfs_set_token_file_extent_offset(&token, fi, extent_offset);
  	btrfs_set_token_file_extent_num_bytes(&token, fi, em->len);
  	btrfs_set_token_file_extent_ram_bytes(&token, fi, em->ram_bytes);
  	btrfs_set_token_file_extent_compression(&token, fi, em->compress_type);
  	btrfs_set_token_file_extent_encryption(&token, fi, 0);
  	btrfs_set_token_file_extent_other_encoding(&token, fi, 0);
  	btrfs_mark_buffer_dirty(leaf);
  
  	btrfs_release_path(path);
  
  	return ret;
  }
  
  /*
   * Log all prealloc extents beyond the inode's i_size to make sure we do not
   * lose them after doing a fast fsync and replaying the log. We scan the
   * subvolume's root instead of iterating the inode's extent map tree because
   * otherwise we can log incorrect extent items based on extent map conversion.
   * That can happen due to the fact that extent maps are merged when they
   * are not in the extent map tree's list of modified extents.
   */
  static int btrfs_log_prealloc_extents(struct btrfs_trans_handle *trans,
  				      struct btrfs_inode *inode,
  				      struct btrfs_path *path)
  {
  	struct btrfs_root *root = inode->root;
  	struct btrfs_key key;
  	const u64 i_size = i_size_read(&inode->vfs_inode);
  	const u64 ino = btrfs_ino(inode);
  	struct btrfs_path *dst_path = NULL;
  	bool dropped_extents = false;
  	u64 truncate_offset = i_size;
  	struct extent_buffer *leaf;
  	int slot;
  	int ins_nr = 0;
  	int start_slot;
  	int ret;
  
  	if (!(inode->flags & BTRFS_INODE_PREALLOC))
  		return 0;
  
  	key.objectid = ino;
  	key.type = BTRFS_EXTENT_DATA_KEY;
  	key.offset = i_size;
  	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
  	if (ret < 0)
  		goto out;
  
  	/*
  	 * We must check if there is a prealloc extent that starts before the
  	 * i_size and crosses the i_size boundary. This is to ensure later we
  	 * truncate down to the end of that extent and not to the i_size, as
  	 * otherwise we end up losing part of the prealloc extent after a log
  	 * replay and with an implicit hole if there is another prealloc extent
  	 * that starts at an offset beyond i_size.
  	 */
  	ret = btrfs_previous_item(root, path, ino, BTRFS_EXTENT_DATA_KEY);
  	if (ret < 0)
  		goto out;
  
  	if (ret == 0) {
  		struct btrfs_file_extent_item *ei;
  
  		leaf = path->nodes[0];
  		slot = path->slots[0];
  		ei = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
  
  		if (btrfs_file_extent_type(leaf, ei) ==
  		    BTRFS_FILE_EXTENT_PREALLOC) {
  			u64 extent_end;
  
  			btrfs_item_key_to_cpu(leaf, &key, slot);
  			extent_end = key.offset +
  				btrfs_file_extent_num_bytes(leaf, ei);
  
  			if (extent_end > i_size)
  				truncate_offset = extent_end;
  		}
  	} else {
  		ret = 0;
  	}
  
  	while (true) {
  		leaf = path->nodes[0];
  		slot = path->slots[0];
  
  		if (slot >= btrfs_header_nritems(leaf)) {
  			if (ins_nr > 0) {
  				ret = copy_items(trans, inode, dst_path, path,
  						 start_slot, ins_nr, 1, 0);
  				if (ret < 0)
  					goto out;
  				ins_nr = 0;
  			}
  			ret = btrfs_next_leaf(root, path);
  			if (ret < 0)
  				goto out;
  			if (ret > 0) {
  				ret = 0;
  				break;
  			}
  			continue;
  		}
  
  		btrfs_item_key_to_cpu(leaf, &key, slot);
  		if (key.objectid > ino)
  			break;
  		if (WARN_ON_ONCE(key.objectid < ino) ||
  		    key.type < BTRFS_EXTENT_DATA_KEY ||
  		    key.offset < i_size) {
  			path->slots[0]++;
  			continue;
  		}
  		if (!dropped_extents) {
  			/*
  			 * Avoid logging extent items logged in past fsync calls
  			 * and leading to duplicate keys in the log tree.
  			 */
  			do {
  				ret = btrfs_truncate_inode_items(trans,
  							 root->log_root,
  							 inode, truncate_offset,
  							 BTRFS_EXTENT_DATA_KEY,
  							 NULL);
  			} while (ret == -EAGAIN);
  			if (ret)
  				goto out;
  			dropped_extents = true;
  		}
  		if (ins_nr == 0)
  			start_slot = slot;
  		ins_nr++;
  		path->slots[0]++;
  		if (!dst_path) {
  			dst_path = btrfs_alloc_path();
  			if (!dst_path) {
  				ret = -ENOMEM;
  				goto out;
  			}
  		}
  	}
  	if (ins_nr > 0)
  		ret = copy_items(trans, inode, dst_path, path,
  				 start_slot, ins_nr, 1, 0);
  out:
  	btrfs_release_path(path);
  	btrfs_free_path(dst_path);
  	return ret;
  }
  
  static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans,
  				     struct btrfs_root *root,
  				     struct btrfs_inode *inode,
  				     struct btrfs_path *path,
  				     struct btrfs_log_ctx *ctx)
  {
  	struct btrfs_ordered_extent *ordered;
  	struct btrfs_ordered_extent *tmp;
  	struct extent_map *em, *n;
  	struct list_head extents;
  	struct extent_map_tree *tree = &inode->extent_tree;
  	int ret = 0;
  	int num = 0;
  
  	INIT_LIST_HEAD(&extents);
  
  	write_lock(&tree->lock);
  
  	list_for_each_entry_safe(em, n, &tree->modified_extents, list) {
  		list_del_init(&em->list);
  		/*
  		 * Just an arbitrary number, this can be really CPU intensive
  		 * once we start getting a lot of extents, and really once we
  		 * have a bunch of extents we just want to commit since it will
  		 * be faster.
  		 */
  		if (++num > 32768) {
  			list_del_init(&tree->modified_extents);
  			ret = -EFBIG;
  			goto process;
  		}
  
  		if (em->generation < trans->transid)
  			continue;
  
  		/* We log prealloc extents beyond eof later. */
  		if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) &&
  		    em->start >= i_size_read(&inode->vfs_inode))
  			continue;
  
  		/* Need a ref to keep it from getting evicted from cache */
  		refcount_inc(&em->refs);
  		set_bit(EXTENT_FLAG_LOGGING, &em->flags);
  		list_add_tail(&em->list, &extents);
  		num++;
  	}
  
  	list_sort(NULL, &extents, extent_cmp);
  process:
  	while (!list_empty(&extents)) {
  		em = list_entry(extents.next, struct extent_map, list);
  
  		list_del_init(&em->list);
  
  		/*
  		 * If we had an error we just need to delete everybody from our
  		 * private list.
  		 */
  		if (ret) {
  			clear_em_logging(tree, em);
  			free_extent_map(em);
  			continue;
  		}
  
  		write_unlock(&tree->lock);
  
  		ret = log_one_extent(trans, inode, root, em, path, ctx);
  		write_lock(&tree->lock);
  		clear_em_logging(tree, em);
  		free_extent_map(em);
  	}
  	WARN_ON(!list_empty(&extents));
  	write_unlock(&tree->lock);
  
  	btrfs_release_path(path);
  	if (!ret)
  		ret = btrfs_log_prealloc_extents(trans, inode, path);
  	if (ret)
  		return ret;
  
  	/*
  	 * We have logged all extents successfully, now make sure the commit of
  	 * the current transaction waits for the ordered extents to complete
  	 * before it commits and wipes out the log trees, otherwise we would
  	 * lose data if an ordered extents completes after the transaction
  	 * commits and a power failure happens after the transaction commit.
  	 */
  	list_for_each_entry_safe(ordered, tmp, &ctx->ordered_extents, log_list) {
  		list_del_init(&ordered->log_list);
  		set_bit(BTRFS_ORDERED_LOGGED, &ordered->flags);
  
  		if (!test_bit(BTRFS_ORDERED_COMPLETE, &ordered->flags)) {
  			spin_lock_irq(&inode->ordered_tree.lock);
  			if (!test_bit(BTRFS_ORDERED_COMPLETE, &ordered->flags)) {
  				set_bit(BTRFS_ORDERED_PENDING, &ordered->flags);
  				atomic_inc(&trans->transaction->pending_ordered);
  			}
  			spin_unlock_irq(&inode->ordered_tree.lock);
  		}
  		btrfs_put_ordered_extent(ordered);
  	}
  
  	return 0;
  }
  
  static int logged_inode_size(struct btrfs_root *log, struct btrfs_inode *inode,
  			     struct btrfs_path *path, u64 *size_ret)
  {
  	struct btrfs_key key;
  	int ret;
  
  	key.objectid = btrfs_ino(inode);
  	key.type = BTRFS_INODE_ITEM_KEY;
  	key.offset = 0;
  
  	ret = btrfs_search_slot(NULL, log, &key, path, 0, 0);
  	if (ret < 0) {
  		return ret;
  	} else if (ret > 0) {
  		*size_ret = 0;
  	} else {
  		struct btrfs_inode_item *item;
  
  		item = btrfs_item_ptr(path->nodes[0], path->slots[0],
  				      struct btrfs_inode_item);
  		*size_ret = btrfs_inode_size(path->nodes[0], item);
  		/*
  		 * If the in-memory inode's i_size is smaller then the inode
  		 * size stored in the btree, return the inode's i_size, so
  		 * that we get a correct inode size after replaying the log
  		 * when before a power failure we had a shrinking truncate
  		 * followed by addition of a new name (rename / new hard link).
  		 * Otherwise return the inode size from the btree, to avoid
  		 * data loss when replaying a log due to previously doing a
  		 * write that expands the inode's size and logging a new name
  		 * immediately after.
  		 */
  		if (*size_ret > inode->vfs_inode.i_size)
  			*size_ret = inode->vfs_inode.i_size;
  	}
  
  	btrfs_release_path(path);
  	return 0;
  }
  
  /*
   * At the moment we always log all xattrs. This is to figure out at log replay
   * time which xattrs must have their deletion replayed. If a xattr is missing
   * in the log tree and exists in the fs/subvol tree, we delete it. This is
   * because if a xattr is deleted, the inode is fsynced and a power failure
   * happens, causing the log to be replayed the next time the fs is mounted,
   * we want the xattr to not exist anymore (same behaviour as other filesystems
   * with a journal, ext3/4, xfs, f2fs, etc).
   */
  static int btrfs_log_all_xattrs(struct btrfs_trans_handle *trans,
  				struct btrfs_root *root,
  				struct btrfs_inode *inode,
  				struct btrfs_path *path,
  				struct btrfs_path *dst_path)
  {
  	int ret;
  	struct btrfs_key key;
  	const u64 ino = btrfs_ino(inode);
  	int ins_nr = 0;
  	int start_slot = 0;
  	bool found_xattrs = false;
  
  	if (test_bit(BTRFS_INODE_NO_XATTRS, &inode->runtime_flags))
  		return 0;
  
  	key.objectid = ino;
  	key.type = BTRFS_XATTR_ITEM_KEY;
  	key.offset = 0;
  
  	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
  	if (ret < 0)
  		return ret;
  
  	while (true) {
  		int slot = path->slots[0];
  		struct extent_buffer *leaf = path->nodes[0];
  		int nritems = btrfs_header_nritems(leaf);
  
  		if (slot >= nritems) {
  			if (ins_nr > 0) {
  				ret = copy_items(trans, inode, dst_path, path,
  						 start_slot, ins_nr, 1, 0);
  				if (ret < 0)
  					return ret;
  				ins_nr = 0;
  			}
  			ret = btrfs_next_leaf(root, path);
  			if (ret < 0)
  				return ret;
  			else if (ret > 0)
  				break;
  			continue;
  		}
  
  		btrfs_item_key_to_cpu(leaf, &key, slot);
  		if (key.objectid != ino || key.type != BTRFS_XATTR_ITEM_KEY)
  			break;
  
  		if (ins_nr == 0)
  			start_slot = slot;
  		ins_nr++;
  		path->slots[0]++;
  		found_xattrs = true;
  		cond_resched();
  	}
  	if (ins_nr > 0) {
  		ret = copy_items(trans, inode, dst_path, path,
  				 start_slot, ins_nr, 1, 0);
  		if (ret < 0)
  			return ret;
  	}
  
  	if (!found_xattrs)
  		set_bit(BTRFS_INODE_NO_XATTRS, &inode->runtime_flags);
  
  	return 0;
  }
  
  /*
   * When using the NO_HOLES feature if we punched a hole that causes the
   * deletion of entire leafs or all the extent items of the first leaf (the one
   * that contains the inode item and references) we may end up not processing
   * any extents, because there are no leafs with a generation matching the
   * current transaction that have extent items for our inode. So we need to find
   * if any holes exist and then log them. We also need to log holes after any
   * truncate operation that changes the inode's size.
   */
  static int btrfs_log_holes(struct btrfs_trans_handle *trans,
  			   struct btrfs_root *root,
  			   struct btrfs_inode *inode,
  			   struct btrfs_path *path)
  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	struct btrfs_key key;
  	const u64 ino = btrfs_ino(inode);
  	const u64 i_size = i_size_read(&inode->vfs_inode);
  	u64 prev_extent_end = 0;
  	int ret;
  
  	if (!btrfs_fs_incompat(fs_info, NO_HOLES) || i_size == 0)
  		return 0;
  
  	key.objectid = ino;
  	key.type = BTRFS_EXTENT_DATA_KEY;
  	key.offset = 0;
  
  	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
  	if (ret < 0)
  		return ret;
  
  	while (true) {
  		struct extent_buffer *leaf = path->nodes[0];
  
  		if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
  			ret = btrfs_next_leaf(root, path);
  			if (ret < 0)
  				return ret;
  			if (ret > 0) {
  				ret = 0;
  				break;
  			}
  			leaf = path->nodes[0];
  		}
  
  		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
  		if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY)
  			break;
  
  		/* We have a hole, log it. */
  		if (prev_extent_end < key.offset) {
  			const u64 hole_len = key.offset - prev_extent_end;
  
  			/*
  			 * Release the path to avoid deadlocks with other code
  			 * paths that search the root while holding locks on
  			 * leafs from the log root.
  			 */
  			btrfs_release_path(path);
  			ret = btrfs_insert_file_extent(trans, root->log_root,
  						       ino, prev_extent_end, 0,
  						       0, hole_len, 0, hole_len,
  						       0, 0, 0);
  			if (ret < 0)
  				return ret;
  
  			/*
  			 * Search for the same key again in the root. Since it's
  			 * an extent item and we are holding the inode lock, the
  			 * key must still exist. If it doesn't just emit warning
  			 * and return an error to fall back to a transaction
  			 * commit.
  			 */
  			ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
  			if (ret < 0)
  				return ret;
  			if (WARN_ON(ret > 0))
  				return -ENOENT;
  			leaf = path->nodes[0];
  		}
  
  		prev_extent_end = btrfs_file_extent_end(path);
  		path->slots[0]++;
  		cond_resched();
  	}
  
  	if (prev_extent_end < i_size) {
  		u64 hole_len;
  
  		btrfs_release_path(path);
  		hole_len = ALIGN(i_size - prev_extent_end, fs_info->sectorsize);
  		ret = btrfs_insert_file_extent(trans, root->log_root,
  					       ino, prev_extent_end, 0, 0,
  					       hole_len, 0, hole_len,
  					       0, 0, 0);
  		if (ret < 0)
  			return ret;
  	}
  
  	return 0;
  }
  
  /*
   * When we are logging a new inode X, check if it doesn't have a reference that
   * matches the reference from some other inode Y created in a past transaction
   * and that was renamed in the current transaction. If we don't do this, then at
   * log replay time we can lose inode Y (and all its files if it's a directory):
   *
   * mkdir /mnt/x
   * echo "hello world" > /mnt/x/foobar
   * sync
   * mv /mnt/x /mnt/y
   * mkdir /mnt/x                 # or touch /mnt/x
   * xfs_io -c fsync /mnt/x
   * <power fail>
   * mount fs, trigger log replay
   *
   * After the log replay procedure, we would lose the first directory and all its
   * files (file foobar).
   * For the case where inode Y is not a directory we simply end up losing it:
   *
   * echo "123" > /mnt/foo
   * sync
   * mv /mnt/foo /mnt/bar
   * echo "abc" > /mnt/foo
   * xfs_io -c fsync /mnt/foo
   * <power fail>
   *
   * We also need this for cases where a snapshot entry is replaced by some other
   * entry (file or directory) otherwise we end up with an unreplayable log due to
   * attempts to delete the snapshot entry (entry of type BTRFS_ROOT_ITEM_KEY) as
   * if it were a regular entry:
   *
   * mkdir /mnt/x
   * btrfs subvolume snapshot /mnt /mnt/x/snap
   * btrfs subvolume delete /mnt/x/snap
   * rmdir /mnt/x
   * mkdir /mnt/x
   * fsync /mnt/x or fsync some new file inside it
   * <power fail>
   *
   * The snapshot delete, rmdir of x, mkdir of a new x and the fsync all happen in
   * the same transaction.
   */
  static int btrfs_check_ref_name_override(struct extent_buffer *eb,
  					 const int slot,
  					 const struct btrfs_key *key,
  					 struct btrfs_inode *inode,
  					 u64 *other_ino, u64 *other_parent)
  {
  	int ret;
  	struct btrfs_path *search_path;
  	char *name = NULL;
  	u32 name_len = 0;
  	u32 item_size = btrfs_item_size_nr(eb, slot);
  	u32 cur_offset = 0;
  	unsigned long ptr = btrfs_item_ptr_offset(eb, slot);
  
  	search_path = btrfs_alloc_path();
  	if (!search_path)
  		return -ENOMEM;
  	search_path->search_commit_root = 1;
  	search_path->skip_locking = 1;
  
  	while (cur_offset < item_size) {
  		u64 parent;
  		u32 this_name_len;
  		u32 this_len;
  		unsigned long name_ptr;
  		struct btrfs_dir_item *di;
  
  		if (key->type == BTRFS_INODE_REF_KEY) {
  			struct btrfs_inode_ref *iref;
  
  			iref = (struct btrfs_inode_ref *)(ptr + cur_offset);
  			parent = key->offset;
  			this_name_len = btrfs_inode_ref_name_len(eb, iref);
  			name_ptr = (unsigned long)(iref + 1);
  			this_len = sizeof(*iref) + this_name_len;
  		} else {
  			struct btrfs_inode_extref *extref;
  
  			extref = (struct btrfs_inode_extref *)(ptr +
  							       cur_offset);
  			parent = btrfs_inode_extref_parent(eb, extref);
  			this_name_len = btrfs_inode_extref_name_len(eb, extref);
  			name_ptr = (unsigned long)&extref->name;
  			this_len = sizeof(*extref) + this_name_len;
  		}
  
  		if (this_name_len > name_len) {
  			char *new_name;
  
  			new_name = krealloc(name, this_name_len, GFP_NOFS);
  			if (!new_name) {
  				ret = -ENOMEM;
  				goto out;
  			}
  			name_len = this_name_len;
  			name = new_name;
  		}
  
  		read_extent_buffer(eb, name, name_ptr, this_name_len);
  		di = btrfs_lookup_dir_item(NULL, inode->root, search_path,
  				parent, name, this_name_len, 0);
  		if (di && !IS_ERR(di)) {
  			struct btrfs_key di_key;
  
  			btrfs_dir_item_key_to_cpu(search_path->nodes[0],
  						  di, &di_key);
  			if (di_key.type == BTRFS_INODE_ITEM_KEY) {
  				if (di_key.objectid != key->objectid) {
  					ret = 1;
  					*other_ino = di_key.objectid;
  					*other_parent = parent;
  				} else {
  					ret = 0;
  				}
  			} else {
  				ret = -EAGAIN;
  			}
  			goto out;
  		} else if (IS_ERR(di)) {
  			ret = PTR_ERR(di);
  			goto out;
  		}
  		btrfs_release_path(search_path);
  
  		cur_offset += this_len;
  	}
  	ret = 0;
  out:
  	btrfs_free_path(search_path);
  	kfree(name);
  	return ret;
  }
  
  struct btrfs_ino_list {
  	u64 ino;
  	u64 parent;
  	struct list_head list;
  };
  
  static int log_conflicting_inodes(struct btrfs_trans_handle *trans,
  				  struct btrfs_root *root,
  				  struct btrfs_path *path,
  				  struct btrfs_log_ctx *ctx,
  				  u64 ino, u64 parent)
  {
  	struct btrfs_ino_list *ino_elem;
  	LIST_HEAD(inode_list);
  	int ret = 0;
  
  	ino_elem = kmalloc(sizeof(*ino_elem), GFP_NOFS);
  	if (!ino_elem)
  		return -ENOMEM;
  	ino_elem->ino = ino;
  	ino_elem->parent = parent;
  	list_add_tail(&ino_elem->list, &inode_list);
  
  	while (!list_empty(&inode_list)) {
  		struct btrfs_fs_info *fs_info = root->fs_info;
  		struct btrfs_key key;
  		struct inode *inode;
  
  		ino_elem = list_first_entry(&inode_list, struct btrfs_ino_list,
  					    list);
  		ino = ino_elem->ino;
  		parent = ino_elem->parent;
  		list_del(&ino_elem->list);
  		kfree(ino_elem);
  		if (ret)
  			continue;
  
  		btrfs_release_path(path);
  
  		inode = btrfs_iget(fs_info->sb, ino, root);
  		/*
  		 * If the other inode that had a conflicting dir entry was
  		 * deleted in the current transaction, we need to log its parent
  		 * directory.
  		 */
  		if (IS_ERR(inode)) {
  			ret = PTR_ERR(inode);
  			if (ret == -ENOENT) {
  				inode = btrfs_iget(fs_info->sb, parent, root);
  				if (IS_ERR(inode)) {
  					ret = PTR_ERR(inode);
  				} else {
  					ret = btrfs_log_inode(trans, root,
  						      BTRFS_I(inode),
  						      LOG_OTHER_INODE_ALL,
  						      ctx);
  					btrfs_add_delayed_iput(inode);
  				}
  			}
  			continue;
  		}
  		/*
  		 * If the inode was already logged skip it - otherwise we can
  		 * hit an infinite loop. Example:
  		 *
  		 * From the commit root (previous transaction) we have the
  		 * following inodes:
  		 *
  		 * inode 257 a directory
  		 * inode 258 with references "zz" and "zz_link" on inode 257
  		 * inode 259 with reference "a" on inode 257
  		 *
  		 * And in the current (uncommitted) transaction we have:
  		 *
  		 * inode 257 a directory, unchanged
  		 * inode 258 with references "a" and "a2" on inode 257
  		 * inode 259 with reference "zz_link" on inode 257
  		 * inode 261 with reference "zz" on inode 257
  		 *
  		 * When logging inode 261 the following infinite loop could
  		 * happen if we don't skip already logged inodes:
  		 *
  		 * - we detect inode 258 as a conflicting inode, with inode 261
  		 *   on reference "zz", and log it;
  		 *
  		 * - we detect inode 259 as a conflicting inode, with inode 258
  		 *   on reference "a", and log it;
  		 *
  		 * - we detect inode 258 as a conflicting inode, with inode 259
  		 *   on reference "zz_link", and log it - again! After this we
  		 *   repeat the above steps forever.
  		 */
  		spin_lock(&BTRFS_I(inode)->lock);
  		/*
  		 * Check the inode's logged_trans only instead of
  		 * btrfs_inode_in_log(). This is because the last_log_commit of
  		 * the inode is not updated when we only log that it exists (see
  		 * btrfs_log_inode()).
  		 */
  		if (BTRFS_I(inode)->logged_trans == trans->transid) {
  			spin_unlock(&BTRFS_I(inode)->lock);
  			btrfs_add_delayed_iput(inode);
  			continue;
  		}
  		spin_unlock(&BTRFS_I(inode)->lock);
  		/*
  		 * We are safe logging the other inode without acquiring its
  		 * lock as long as we log with the LOG_INODE_EXISTS mode. We
  		 * are safe against concurrent renames of the other inode as
  		 * well because during a rename we pin the log and update the
  		 * log with the new name before we unpin it.
  		 */
  		ret = btrfs_log_inode(trans, root, BTRFS_I(inode),
  				      LOG_OTHER_INODE, ctx);
  		if (ret) {
  			btrfs_add_delayed_iput(inode);
  			continue;
  		}
  
  		key.objectid = ino;
  		key.type = BTRFS_INODE_REF_KEY;
  		key.offset = 0;
  		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
  		if (ret < 0) {
  			btrfs_add_delayed_iput(inode);
  			continue;
  		}
  
  		while (true) {
  			struct extent_buffer *leaf = path->nodes[0];
  			int slot = path->slots[0];
  			u64 other_ino = 0;
  			u64 other_parent = 0;
  
  			if (slot >= btrfs_header_nritems(leaf)) {
  				ret = btrfs_next_leaf(root, path);
  				if (ret < 0) {
  					break;
  				} else if (ret > 0) {
  					ret = 0;
  					break;
  				}
  				continue;
  			}
  
  			btrfs_item_key_to_cpu(leaf, &key, slot);
  			if (key.objectid != ino ||
  			    (key.type != BTRFS_INODE_REF_KEY &&
  			     key.type != BTRFS_INODE_EXTREF_KEY)) {
  				ret = 0;
  				break;
  			}
  
  			ret = btrfs_check_ref_name_override(leaf, slot, &key,
  					BTRFS_I(inode), &other_ino,
  					&other_parent);
  			if (ret < 0)
  				break;
  			if (ret > 0) {
  				ino_elem = kmalloc(sizeof(*ino_elem), GFP_NOFS);
  				if (!ino_elem) {
  					ret = -ENOMEM;
  					break;
  				}
  				ino_elem->ino = other_ino;
  				ino_elem->parent = other_parent;
  				list_add_tail(&ino_elem->list, &inode_list);
  				ret = 0;
  			}
  			path->slots[0]++;
  		}
  		btrfs_add_delayed_iput(inode);
  	}
  
  	return ret;
  }
  
  static int copy_inode_items_to_log(struct btrfs_trans_handle *trans,
  				   struct btrfs_inode *inode,
  				   struct btrfs_key *min_key,
  				   const struct btrfs_key *max_key,
  				   struct btrfs_path *path,
  				   struct btrfs_path *dst_path,
  				   const u64 logged_isize,
  				   const bool recursive_logging,
  				   const int inode_only,
  				   struct btrfs_log_ctx *ctx,
  				   bool *need_log_inode_item)
  {
  	struct btrfs_root *root = inode->root;
  	int ins_start_slot = 0;
  	int ins_nr = 0;
  	int ret;
  
  	while (1) {
  		ret = btrfs_search_forward(root, min_key, path, trans->transid);
  		if (ret < 0)
  			return ret;
  		if (ret > 0) {
  			ret = 0;
  			break;
  		}
  again:
  		/* Note, ins_nr might be > 0 here, cleanup outside the loop */
  		if (min_key->objectid != max_key->objectid)
  			break;
  		if (min_key->type > max_key->type)
  			break;
  
  		if (min_key->type == BTRFS_INODE_ITEM_KEY)
  			*need_log_inode_item = false;
  
  		if ((min_key->type == BTRFS_INODE_REF_KEY ||
  		     min_key->type == BTRFS_INODE_EXTREF_KEY) &&
  		    inode->generation == trans->transid &&
  		    !recursive_logging) {
  			u64 other_ino = 0;
  			u64 other_parent = 0;
  
  			ret = btrfs_check_ref_name_override(path->nodes[0],
  					path->slots[0], min_key, inode,
  					&other_ino, &other_parent);
  			if (ret < 0) {
  				return ret;
  			} else if (ret > 0 && ctx &&
  				   other_ino != btrfs_ino(BTRFS_I(ctx->inode))) {
  				if (ins_nr > 0) {
  					ins_nr++;
  				} else {
  					ins_nr = 1;
  					ins_start_slot = path->slots[0];
  				}
  				ret = copy_items(trans, inode, dst_path, path,
  						 ins_start_slot, ins_nr,
  						 inode_only, logged_isize);
  				if (ret < 0)
  					return ret;
  				ins_nr = 0;
  
  				ret = log_conflicting_inodes(trans, root, path,
  						ctx, other_ino, other_parent);
  				if (ret)
  					return ret;
  				btrfs_release_path(path);
  				goto next_key;
  			}
  		}
  
  		/* Skip xattrs, we log them later with btrfs_log_all_xattrs() */
  		if (min_key->type == BTRFS_XATTR_ITEM_KEY) {
  			if (ins_nr == 0)
  				goto next_slot;
  			ret = copy_items(trans, inode, dst_path, path,
  					 ins_start_slot,
  					 ins_nr, inode_only, logged_isize);
  			if (ret < 0)
  				return ret;
  			ins_nr = 0;
  			goto next_slot;
  		}
  
  		if (ins_nr && ins_start_slot + ins_nr == path->slots[0]) {
  			ins_nr++;
  			goto next_slot;
  		} else if (!ins_nr) {
  			ins_start_slot = path->slots[0];
  			ins_nr = 1;
  			goto next_slot;
  		}
  
  		ret = copy_items(trans, inode, dst_path, path, ins_start_slot,
  				 ins_nr, inode_only, logged_isize);
  		if (ret < 0)
  			return ret;
  		ins_nr = 1;
  		ins_start_slot = path->slots[0];
  next_slot:
  		path->slots[0]++;
  		if (path->slots[0] < btrfs_header_nritems(path->nodes[0])) {
  			btrfs_item_key_to_cpu(path->nodes[0], min_key,
  					      path->slots[0]);
  			goto again;
  		}
  		if (ins_nr) {
  			ret = copy_items(trans, inode, dst_path, path,
  					 ins_start_slot, ins_nr, inode_only,
  					 logged_isize);
  			if (ret < 0)
  				return ret;
  			ins_nr = 0;
  		}
  		btrfs_release_path(path);
  next_key:
  		if (min_key->offset < (u64)-1) {
  			min_key->offset++;
  		} else if (min_key->type < max_key->type) {
  			min_key->type++;
  			min_key->offset = 0;
  		} else {
  			break;
  		}
  	}
  	if (ins_nr)
  		ret = copy_items(trans, inode, dst_path, path, ins_start_slot,
  				 ins_nr, inode_only, logged_isize);
  
  	return ret;
  }
  
  /* log a single inode in the tree log.
   * At least one parent directory for this inode must exist in the tree
   * or be logged already.
   *
   * Any items from this inode changed by the current transaction are copied
   * to the log tree.  An extra reference is taken on any extents in this
   * file, allowing us to avoid a whole pile of corner cases around logging
   * blocks that have been removed from the tree.
   *
   * See LOG_INODE_ALL and related defines for a description of what inode_only
   * does.
   *
   * This handles both files and directories.
   */
  static int btrfs_log_inode(struct btrfs_trans_handle *trans,
  			   struct btrfs_root *root, struct btrfs_inode *inode,
  			   int inode_only,
  			   struct btrfs_log_ctx *ctx)
  {
  	struct btrfs_path *path;
  	struct btrfs_path *dst_path;
  	struct btrfs_key min_key;
  	struct btrfs_key max_key;
  	struct btrfs_root *log = root->log_root;
  	int err = 0;
  	int ret = 0;
  	bool fast_search = false;
  	u64 ino = btrfs_ino(inode);
  	struct extent_map_tree *em_tree = &inode->extent_tree;
  	u64 logged_isize = 0;
  	bool need_log_inode_item = true;
  	bool xattrs_logged = false;
  	bool recursive_logging = false;
  	bool inode_item_dropped = true;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  	dst_path = btrfs_alloc_path();
  	if (!dst_path) {
  		btrfs_free_path(path);
  		return -ENOMEM;
  	}
  
  	min_key.objectid = ino;
  	min_key.type = BTRFS_INODE_ITEM_KEY;
  	min_key.offset = 0;
  
  	max_key.objectid = ino;
  
  
  	/* today the code can only do partial logging of directories */
  	if (S_ISDIR(inode->vfs_inode.i_mode) ||
  	    (!test_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
  		       &inode->runtime_flags) &&
  	     inode_only >= LOG_INODE_EXISTS))
  		max_key.type = BTRFS_XATTR_ITEM_KEY;
  	else
  		max_key.type = (u8)-1;
  	max_key.offset = (u64)-1;
  
  	/*
  	 * Only run delayed items if we are a directory. We want to make sure
  	 * all directory indexes hit the fs/subvolume tree so we can find them
  	 * and figure out which index ranges have to be logged.
  	 *
  	 * Otherwise commit the delayed inode only if the full sync flag is set,
  	 * as we want to make sure an up to date version is in the subvolume
  	 * tree so copy_inode_items_to_log() / copy_items() can find it and copy
  	 * it to the log tree. For a non full sync, we always log the inode item
  	 * based on the in-memory struct btrfs_inode which is always up to date.
  	 */
  	if (S_ISDIR(inode->vfs_inode.i_mode))
  		ret = btrfs_commit_inode_delayed_items(trans, inode);
  	else if (test_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &inode->runtime_flags))
  		ret = btrfs_commit_inode_delayed_inode(inode);
  
  	if (ret) {
  		btrfs_free_path(path);
  		btrfs_free_path(dst_path);
  		return ret;
  	}
  
  	if (inode_only == LOG_OTHER_INODE || inode_only == LOG_OTHER_INODE_ALL) {
  		recursive_logging = true;
  		if (inode_only == LOG_OTHER_INODE)
  			inode_only = LOG_INODE_EXISTS;
  		else
  			inode_only = LOG_INODE_ALL;
  		mutex_lock_nested(&inode->log_mutex, SINGLE_DEPTH_NESTING);
  	} else {
  		mutex_lock(&inode->log_mutex);
  	}
  
  	/*
  	 * This is for cases where logging a directory could result in losing a
  	 * a file after replaying the log. For example, if we move a file from a
  	 * directory A to a directory B, then fsync directory A, we have no way
  	 * to known the file was moved from A to B, so logging just A would
  	 * result in losing the file after a log replay.
  	 */
  	if (S_ISDIR(inode->vfs_inode.i_mode) &&
  	    inode_only == LOG_INODE_ALL &&
  	    inode->last_unlink_trans >= trans->transid) {
  		btrfs_set_log_full_commit(trans);
  		err = 1;
  		goto out_unlock;
  	}
  
  	/*
  	 * a brute force approach to making sure we get the most uptodate
  	 * copies of everything.
  	 */
  	if (S_ISDIR(inode->vfs_inode.i_mode)) {
  		int max_key_type = BTRFS_DIR_LOG_INDEX_KEY;
  
  		clear_bit(BTRFS_INODE_COPY_EVERYTHING, &inode->runtime_flags);
  		if (inode_only == LOG_INODE_EXISTS)
  			max_key_type = BTRFS_XATTR_ITEM_KEY;
  		ret = drop_objectid_items(trans, log, path, ino, max_key_type);
  	} else {
  		if (inode_only == LOG_INODE_EXISTS) {
  			/*
  			 * Make sure the new inode item we write to the log has
  			 * the same isize as the current one (if it exists).
  			 * This is necessary to prevent data loss after log
  			 * replay, and also to prevent doing a wrong expanding
  			 * truncate - for e.g. create file, write 4K into offset
  			 * 0, fsync, write 4K into offset 4096, add hard link,
  			 * fsync some other file (to sync log), power fail - if
  			 * we use the inode's current i_size, after log replay
  			 * we get a 8Kb file, with the last 4Kb extent as a hole
  			 * (zeroes), as if an expanding truncate happened,
  			 * instead of getting a file of 4Kb only.
  			 */
  			err = logged_inode_size(log, inode, path, &logged_isize);
  			if (err)
  				goto out_unlock;
  		}
  		if (test_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
  			     &inode->runtime_flags)) {
  			if (inode_only == LOG_INODE_EXISTS) {
  				max_key.type = BTRFS_XATTR_ITEM_KEY;
  				ret = drop_objectid_items(trans, log, path, ino,
  							  max_key.type);
  			} else {
  				clear_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
  					  &inode->runtime_flags);
  				clear_bit(BTRFS_INODE_COPY_EVERYTHING,
  					  &inode->runtime_flags);
  				while(1) {
  					ret = btrfs_truncate_inode_items(trans,
  						log, inode, 0, 0, NULL);
  					if (ret != -EAGAIN)
  						break;
  				}
  			}
  		} else if (test_and_clear_bit(BTRFS_INODE_COPY_EVERYTHING,
  					      &inode->runtime_flags) ||
  			   inode_only == LOG_INODE_EXISTS) {
  			if (inode_only == LOG_INODE_ALL)
  				fast_search = true;
  			max_key.type = BTRFS_XATTR_ITEM_KEY;
  			ret = drop_objectid_items(trans, log, path, ino,
  						  max_key.type);
  		} else {
  			if (inode_only == LOG_INODE_ALL)
  				fast_search = true;
  			inode_item_dropped = false;
  			goto log_extents;
  		}
  
  	}
  	if (ret) {
  		err = ret;
  		goto out_unlock;
  	}
  
  	err = copy_inode_items_to_log(trans, inode, &min_key, &max_key,
  				      path, dst_path, logged_isize,
  				      recursive_logging, inode_only, ctx,
  				      &need_log_inode_item);
  	if (err)
  		goto out_unlock;
  
  	btrfs_release_path(path);
  	btrfs_release_path(dst_path);
  	err = btrfs_log_all_xattrs(trans, root, inode, path, dst_path);
  	if (err)
  		goto out_unlock;
  	xattrs_logged = true;
  	if (max_key.type >= BTRFS_EXTENT_DATA_KEY && !fast_search) {
  		btrfs_release_path(path);
  		btrfs_release_path(dst_path);
  		err = btrfs_log_holes(trans, root, inode, path);
  		if (err)
  			goto out_unlock;
  	}
  log_extents:
  	btrfs_release_path(path);
  	btrfs_release_path(dst_path);
  	if (need_log_inode_item) {
  		err = log_inode_item(trans, log, dst_path, inode, inode_item_dropped);
  		if (err)
  			goto out_unlock;
  		/*
  		 * If we are doing a fast fsync and the inode was logged before
  		 * in this transaction, we don't need to log the xattrs because
  		 * they were logged before. If xattrs were added, changed or
  		 * deleted since the last time we logged the inode, then we have
  		 * already logged them because the inode had the runtime flag
  		 * BTRFS_INODE_COPY_EVERYTHING set.
  		 */
  		if (!xattrs_logged && inode->logged_trans < trans->transid) {
  			err = btrfs_log_all_xattrs(trans, root, inode, path,
  						   dst_path);
  			if (err)
  				goto out_unlock;
  			btrfs_release_path(path);
  		}
  	}
  	if (fast_search) {
  		ret = btrfs_log_changed_extents(trans, root, inode, dst_path,
  						ctx);
  		if (ret) {
  			err = ret;
  			goto out_unlock;
  		}
  	} else if (inode_only == LOG_INODE_ALL) {
  		struct extent_map *em, *n;
  
  		write_lock(&em_tree->lock);
  		list_for_each_entry_safe(em, n, &em_tree->modified_extents, list)
  			list_del_init(&em->list);
  		write_unlock(&em_tree->lock);
  	}
  
  	if (inode_only == LOG_INODE_ALL && S_ISDIR(inode->vfs_inode.i_mode)) {
  		ret = log_directory_changes(trans, root, inode, path, dst_path,
  					ctx);
  		if (ret) {
  			err = ret;
  			goto out_unlock;
  		}
  	}
  
  	/*
  	 * If we are logging that an ancestor inode exists as part of logging a
  	 * new name from a link or rename operation, don't mark the inode as
  	 * logged - otherwise if an explicit fsync is made against an ancestor,
  	 * the fsync considers the inode in the log and doesn't sync the log,
  	 * resulting in the ancestor missing after a power failure unless the
  	 * log was synced as part of an fsync against any other unrelated inode.
  	 * So keep it simple for this case and just don't flag the ancestors as
  	 * logged.
  	 */
  	if (!ctx ||
  	    !(S_ISDIR(inode->vfs_inode.i_mode) && ctx->logging_new_name &&
  	      &inode->vfs_inode != ctx->inode)) {
  		spin_lock(&inode->lock);
  		inode->logged_trans = trans->transid;
  		/*
  		 * Don't update last_log_commit if we logged that an inode exists.
  		 * We do this for two reasons:
  		 *
  		 * 1) We might have had buffered writes to this inode that were
  		 *    flushed and had their ordered extents completed in this
  		 *    transaction, but we did not previously log the inode with
  		 *    LOG_INODE_ALL. Later the inode was evicted and after that
  		 *    it was loaded again and this LOG_INODE_EXISTS log operation
  		 *    happened. We must make sure that if an explicit fsync against
  		 *    the inode is performed later, it logs the new extents, an
  		 *    updated inode item, etc, and syncs the log. The same logic
  		 *    applies to direct IO writes instead of buffered writes.
  		 *
  		 * 2) When we log the inode with LOG_INODE_EXISTS, its inode item
  		 *    is logged with an i_size of 0 or whatever value was logged
  		 *    before. If later the i_size of the inode is increased by a
  		 *    truncate operation, the log is synced through an fsync of
  		 *    some other inode and then finally an explicit fsync against
  		 *    this inode is made, we must make sure this fsync logs the
  		 *    inode with the new i_size, the hole between old i_size and
  		 *    the new i_size, and syncs the log.
  		 */
  		if (inode_only != LOG_INODE_EXISTS)
  			inode->last_log_commit = inode->last_sub_trans;
  		spin_unlock(&inode->lock);
  	}
  out_unlock:
  	mutex_unlock(&inode->log_mutex);
  
  	btrfs_free_path(path);
  	btrfs_free_path(dst_path);
  	return err;
  }
  
  /*
   * Check if we need to log an inode. This is used in contexts where while
   * logging an inode we need to log another inode (either that it exists or in
   * full mode). This is used instead of btrfs_inode_in_log() because the later
   * requires the inode to be in the log and have the log transaction committed,
   * while here we do not care if the log transaction was already committed - our
   * caller will commit the log later - and we want to avoid logging an inode
   * multiple times when multiple tasks have joined the same log transaction.
   */
  static bool need_log_inode(struct btrfs_trans_handle *trans,
  			   struct btrfs_inode *inode)
  {
  	/*
  	 * If a directory was not modified, no dentries added or removed, we can
  	 * and should avoid logging it.
  	 */
  	if (S_ISDIR(inode->vfs_inode.i_mode) && inode->last_trans < trans->transid)
  		return false;
  
  	/*
  	 * If this inode does not have new/updated/deleted xattrs since the last
  	 * time it was logged and is flagged as logged in the current transaction,
  	 * we can skip logging it. As for new/deleted names, those are updated in
  	 * the log by link/unlink/rename operations.
  	 * In case the inode was logged and then evicted and reloaded, its
  	 * logged_trans will be 0, in which case we have to fully log it since
  	 * logged_trans is a transient field, not persisted.
  	 */
  	if (inode->logged_trans == trans->transid &&
  	    !test_bit(BTRFS_INODE_COPY_EVERYTHING, &inode->runtime_flags))
  		return false;
  
  	return true;
  }
  
  struct btrfs_dir_list {
  	u64 ino;
  	struct list_head list;
  };
  
  /*
   * Log the inodes of the new dentries of a directory. See log_dir_items() for
   * details about the why it is needed.
   * This is a recursive operation - if an existing dentry corresponds to a
   * directory, that directory's new entries are logged too (same behaviour as
   * ext3/4, xfs, f2fs, reiserfs, nilfs2). Note that when logging the inodes
   * the dentries point to we do not lock their i_mutex, otherwise lockdep
   * complains about the following circular lock dependency / possible deadlock:
   *
   *        CPU0                                        CPU1
   *        ----                                        ----
   * lock(&type->i_mutex_dir_key#3/2);
   *                                            lock(sb_internal#2);
   *                                            lock(&type->i_mutex_dir_key#3/2);
   * lock(&sb->s_type->i_mutex_key#14);
   *
   * Where sb_internal is the lock (a counter that works as a lock) acquired by
   * sb_start_intwrite() in btrfs_start_transaction().
   * Not locking i_mutex of the inodes is still safe because:
   *
   * 1) For regular files we log with a mode of LOG_INODE_EXISTS. It's possible
   *    that while logging the inode new references (names) are added or removed
   *    from the inode, leaving the logged inode item with a link count that does
   *    not match the number of logged inode reference items. This is fine because
   *    at log replay time we compute the real number of links and correct the
   *    link count in the inode item (see replay_one_buffer() and
   *    link_to_fixup_dir());
   *
   * 2) For directories we log with a mode of LOG_INODE_ALL. It's possible that
   *    while logging the inode's items new items with keys BTRFS_DIR_ITEM_KEY and
   *    BTRFS_DIR_INDEX_KEY are added to fs/subvol tree and the logged inode item
   *    has a size that doesn't match the sum of the lengths of all the logged
   *    names. This does not result in a problem because if a dir_item key is
   *    logged but its matching dir_index key is not logged, at log replay time we
   *    don't use it to replay the respective name (see replay_one_name()). On the
   *    other hand if only the dir_index key ends up being logged, the respective
   *    name is added to the fs/subvol tree with both the dir_item and dir_index
   *    keys created (see replay_one_name()).
   *    The directory's inode item with a wrong i_size is not a problem as well,
   *    since we don't use it at log replay time to set the i_size in the inode
   *    item of the fs/subvol tree (see overwrite_item()).
   */
  static int log_new_dir_dentries(struct btrfs_trans_handle *trans,
  				struct btrfs_root *root,
  				struct btrfs_inode *start_inode,
  				struct btrfs_log_ctx *ctx)
  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	struct btrfs_root *log = root->log_root;
  	struct btrfs_path *path;
  	LIST_HEAD(dir_list);
  	struct btrfs_dir_list *dir_elem;
  	int ret = 0;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	dir_elem = kmalloc(sizeof(*dir_elem), GFP_NOFS);
  	if (!dir_elem) {
  		btrfs_free_path(path);
  		return -ENOMEM;
  	}
  	dir_elem->ino = btrfs_ino(start_inode);
  	list_add_tail(&dir_elem->list, &dir_list);
  
  	while (!list_empty(&dir_list)) {
  		struct extent_buffer *leaf;
  		struct btrfs_key min_key;
  		int nritems;
  		int i;
  
  		dir_elem = list_first_entry(&dir_list, struct btrfs_dir_list,
  					    list);
  		if (ret)
  			goto next_dir_inode;
  
  		min_key.objectid = dir_elem->ino;
  		min_key.type = BTRFS_DIR_ITEM_KEY;
  		min_key.offset = 0;
  again:
  		btrfs_release_path(path);
  		ret = btrfs_search_forward(log, &min_key, path, trans->transid);
  		if (ret < 0) {
  			goto next_dir_inode;
  		} else if (ret > 0) {
  			ret = 0;
  			goto next_dir_inode;
  		}
  
  process_leaf:
  		leaf = path->nodes[0];
  		nritems = btrfs_header_nritems(leaf);
  		for (i = path->slots[0]; i < nritems; i++) {
  			struct btrfs_dir_item *di;
  			struct btrfs_key di_key;
  			struct inode *di_inode;
  			struct btrfs_dir_list *new_dir_elem;
  			int log_mode = LOG_INODE_EXISTS;
  			int type;
  
  			btrfs_item_key_to_cpu(leaf, &min_key, i);
  			if (min_key.objectid != dir_elem->ino ||
  			    min_key.type != BTRFS_DIR_ITEM_KEY)
  				goto next_dir_inode;
  
  			di = btrfs_item_ptr(leaf, i, struct btrfs_dir_item);
  			type = btrfs_dir_type(leaf, di);
  			if (btrfs_dir_transid(leaf, di) < trans->transid &&
  			    type != BTRFS_FT_DIR)
  				continue;
  			btrfs_dir_item_key_to_cpu(leaf, di, &di_key);
  			if (di_key.type == BTRFS_ROOT_ITEM_KEY)
  				continue;
  
  			btrfs_release_path(path);
  			di_inode = btrfs_iget(fs_info->sb, di_key.objectid, root);
  			if (IS_ERR(di_inode)) {
  				ret = PTR_ERR(di_inode);
  				goto next_dir_inode;
  			}
  
  			if (!need_log_inode(trans, BTRFS_I(di_inode))) {
  				btrfs_add_delayed_iput(di_inode);
  				break;
  			}
  
  			ctx->log_new_dentries = false;
  			if (type == BTRFS_FT_DIR || type == BTRFS_FT_SYMLINK)
  				log_mode = LOG_INODE_ALL;
  			ret = btrfs_log_inode(trans, root, BTRFS_I(di_inode),
  					      log_mode, ctx);
  			btrfs_add_delayed_iput(di_inode);
  			if (ret)
  				goto next_dir_inode;
  			if (ctx->log_new_dentries) {
  				new_dir_elem = kmalloc(sizeof(*new_dir_elem),
  						       GFP_NOFS);
  				if (!new_dir_elem) {
  					ret = -ENOMEM;
  					goto next_dir_inode;
  				}
  				new_dir_elem->ino = di_key.objectid;
  				list_add_tail(&new_dir_elem->list, &dir_list);
  			}
  			break;
  		}
  		if (i == nritems) {
  			ret = btrfs_next_leaf(log, path);
  			if (ret < 0) {
  				goto next_dir_inode;
  			} else if (ret > 0) {
  				ret = 0;
  				goto next_dir_inode;
  			}
  			goto process_leaf;
  		}
  		if (min_key.offset < (u64)-1) {
  			min_key.offset++;
  			goto again;
  		}
  next_dir_inode:
  		list_del(&dir_elem->list);
  		kfree(dir_elem);
  	}
  
  	btrfs_free_path(path);
  	return ret;
  }
  
  static int btrfs_log_all_parents(struct btrfs_trans_handle *trans,
  				 struct btrfs_inode *inode,
  				 struct btrfs_log_ctx *ctx)
  {
  	struct btrfs_fs_info *fs_info = trans->fs_info;
  	int ret;
  	struct btrfs_path *path;
  	struct btrfs_key key;
  	struct btrfs_root *root = inode->root;
  	const u64 ino = btrfs_ino(inode);
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  	path->skip_locking = 1;
  	path->search_commit_root = 1;
  
  	key.objectid = ino;
  	key.type = BTRFS_INODE_REF_KEY;
  	key.offset = 0;
  	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
  	if (ret < 0)
  		goto out;
  
  	while (true) {
  		struct extent_buffer *leaf = path->nodes[0];
  		int slot = path->slots[0];
  		u32 cur_offset = 0;
  		u32 item_size;
  		unsigned long ptr;
  
  		if (slot >= btrfs_header_nritems(leaf)) {
  			ret = btrfs_next_leaf(root, path);
  			if (ret < 0)
  				goto out;
  			else if (ret > 0)
  				break;
  			continue;
  		}
  
  		btrfs_item_key_to_cpu(leaf, &key, slot);
  		/* BTRFS_INODE_EXTREF_KEY is BTRFS_INODE_REF_KEY + 1 */
  		if (key.objectid != ino || key.type > BTRFS_INODE_EXTREF_KEY)
  			break;
  
  		item_size = btrfs_item_size_nr(leaf, slot);
  		ptr = btrfs_item_ptr_offset(leaf, slot);
  		while (cur_offset < item_size) {
  			struct btrfs_key inode_key;
  			struct inode *dir_inode;
  
  			inode_key.type = BTRFS_INODE_ITEM_KEY;
  			inode_key.offset = 0;
  
  			if (key.type == BTRFS_INODE_EXTREF_KEY) {
  				struct btrfs_inode_extref *extref;
  
  				extref = (struct btrfs_inode_extref *)
  					(ptr + cur_offset);
  				inode_key.objectid = btrfs_inode_extref_parent(
  					leaf, extref);
  				cur_offset += sizeof(*extref);
  				cur_offset += btrfs_inode_extref_name_len(leaf,
  					extref);
  			} else {
  				inode_key.objectid = key.offset;
  				cur_offset = item_size;
  			}
  
  			dir_inode = btrfs_iget(fs_info->sb, inode_key.objectid,
  					       root);
  			/*
  			 * If the parent inode was deleted, return an error to
  			 * fallback to a transaction commit. This is to prevent
  			 * getting an inode that was moved from one parent A to
  			 * a parent B, got its former parent A deleted and then
  			 * it got fsync'ed, from existing at both parents after
  			 * a log replay (and the old parent still existing).
  			 * Example:
  			 *
  			 * mkdir /mnt/A
  			 * mkdir /mnt/B
  			 * touch /mnt/B/bar
  			 * sync
  			 * mv /mnt/B/bar /mnt/A/bar
  			 * mv -T /mnt/A /mnt/B
  			 * fsync /mnt/B/bar
  			 * <power fail>
  			 *
  			 * If we ignore the old parent B which got deleted,
  			 * after a log replay we would have file bar linked
  			 * at both parents and the old parent B would still
  			 * exist.
  			 */
  			if (IS_ERR(dir_inode)) {
  				ret = PTR_ERR(dir_inode);
  				goto out;
  			}
  
  			if (!need_log_inode(trans, BTRFS_I(dir_inode))) {
  				btrfs_add_delayed_iput(dir_inode);
  				continue;
  			}
  
  			if (ctx)
  				ctx->log_new_dentries = false;
  			ret = btrfs_log_inode(trans, root, BTRFS_I(dir_inode),
  					      LOG_INODE_ALL, ctx);
  			if (!ret && ctx && ctx->log_new_dentries)
  				ret = log_new_dir_dentries(trans, root,
  						   BTRFS_I(dir_inode), ctx);
  			btrfs_add_delayed_iput(dir_inode);
  			if (ret)
  				goto out;
  		}
  		path->slots[0]++;
  	}
  	ret = 0;
  out:
  	btrfs_free_path(path);
  	return ret;
  }
  
  static int log_new_ancestors(struct btrfs_trans_handle *trans,
  			     struct btrfs_root *root,
  			     struct btrfs_path *path,
  			     struct btrfs_log_ctx *ctx)
  {
  	struct btrfs_key found_key;
  
  	btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);
  
  	while (true) {
  		struct btrfs_fs_info *fs_info = root->fs_info;
  		struct extent_buffer *leaf = path->nodes[0];
  		int slot = path->slots[0];
  		struct btrfs_key search_key;
  		struct inode *inode;
  		u64 ino;
  		int ret = 0;
  
  		btrfs_release_path(path);
  
  		ino = found_key.offset;
  
  		search_key.objectid = found_key.offset;
  		search_key.type = BTRFS_INODE_ITEM_KEY;
  		search_key.offset = 0;
  		inode = btrfs_iget(fs_info->sb, ino, root);
  		if (IS_ERR(inode))
  			return PTR_ERR(inode);
  
  		if (BTRFS_I(inode)->generation >= trans->transid &&
  		    need_log_inode(trans, BTRFS_I(inode)))
  			ret = btrfs_log_inode(trans, root, BTRFS_I(inode),
  					      LOG_INODE_EXISTS, ctx);
  		btrfs_add_delayed_iput(inode);
  		if (ret)
  			return ret;
  
  		if (search_key.objectid == BTRFS_FIRST_FREE_OBJECTID)
  			break;
  
  		search_key.type = BTRFS_INODE_REF_KEY;
  		ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
  		if (ret < 0)
  			return ret;
  
  		leaf = path->nodes[0];
  		slot = path->slots[0];
  		if (slot >= btrfs_header_nritems(leaf)) {
  			ret = btrfs_next_leaf(root, path);
  			if (ret < 0)
  				return ret;
  			else if (ret > 0)
  				return -ENOENT;
  			leaf = path->nodes[0];
  			slot = path->slots[0];
  		}
  
  		btrfs_item_key_to_cpu(leaf, &found_key, slot);
  		if (found_key.objectid != search_key.objectid ||
  		    found_key.type != BTRFS_INODE_REF_KEY)
  			return -ENOENT;
  	}
  	return 0;
  }
  
  static int log_new_ancestors_fast(struct btrfs_trans_handle *trans,
  				  struct btrfs_inode *inode,
  				  struct dentry *parent,
  				  struct btrfs_log_ctx *ctx)
  {
  	struct btrfs_root *root = inode->root;
  	struct dentry *old_parent = NULL;
  	struct super_block *sb = inode->vfs_inode.i_sb;
  	int ret = 0;
  
  	while (true) {
  		if (!parent || d_really_is_negative(parent) ||
  		    sb != parent->d_sb)
  			break;
  
  		inode = BTRFS_I(d_inode(parent));
  		if (root != inode->root)
  			break;
  
  		if (inode->generation >= trans->transid &&
  		    need_log_inode(trans, inode)) {
  			ret = btrfs_log_inode(trans, root, inode,
  					      LOG_INODE_EXISTS, ctx);
  			if (ret)
  				break;
  		}
  		if (IS_ROOT(parent))
  			break;
  
  		parent = dget_parent(parent);
  		dput(old_parent);
  		old_parent = parent;
  	}
  	dput(old_parent);
  
  	return ret;
  }
  
  static int log_all_new_ancestors(struct btrfs_trans_handle *trans,
  				 struct btrfs_inode *inode,
  				 struct dentry *parent,
  				 struct btrfs_log_ctx *ctx)
  {
  	struct btrfs_root *root = inode->root;
  	const u64 ino = btrfs_ino(inode);
  	struct btrfs_path *path;
  	struct btrfs_key search_key;
  	int ret;
  
  	/*
  	 * For a single hard link case, go through a fast path that does not
  	 * need to iterate the fs/subvolume tree.
  	 */
  	if (inode->vfs_inode.i_nlink < 2)
  		return log_new_ancestors_fast(trans, inode, parent, ctx);
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	search_key.objectid = ino;
  	search_key.type = BTRFS_INODE_REF_KEY;
  	search_key.offset = 0;
  again:
  	ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
  	if (ret < 0)
  		goto out;
  	if (ret == 0)
  		path->slots[0]++;
  
  	while (true) {
  		struct extent_buffer *leaf = path->nodes[0];
  		int slot = path->slots[0];
  		struct btrfs_key found_key;
  
  		if (slot >= btrfs_header_nritems(leaf)) {
  			ret = btrfs_next_leaf(root, path);
  			if (ret < 0)
  				goto out;
  			else if (ret > 0)
  				break;
  			continue;
  		}
  
  		btrfs_item_key_to_cpu(leaf, &found_key, slot);
  		if (found_key.objectid != ino ||
  		    found_key.type > BTRFS_INODE_EXTREF_KEY)
  			break;
  
  		/*
  		 * Don't deal with extended references because they are rare
  		 * cases and too complex to deal with (we would need to keep
  		 * track of which subitem we are processing for each item in
  		 * this loop, etc). So just return some error to fallback to
  		 * a transaction commit.
  		 */
  		if (found_key.type == BTRFS_INODE_EXTREF_KEY) {
  			ret = -EMLINK;
  			goto out;
  		}
  
  		/*
  		 * Logging ancestors needs to do more searches on the fs/subvol
  		 * tree, so it releases the path as needed to avoid deadlocks.
  		 * Keep track of the last inode ref key and resume from that key
  		 * after logging all new ancestors for the current hard link.
  		 */
  		memcpy(&search_key, &found_key, sizeof(search_key));
  
  		ret = log_new_ancestors(trans, root, path, ctx);
  		if (ret)
  			goto out;
  		btrfs_release_path(path);
  		goto again;
  	}
  	ret = 0;
  out:
  	btrfs_free_path(path);
  	return ret;
  }
  
  /*
   * helper function around btrfs_log_inode to make sure newly created
   * parent directories also end up in the log.  A minimal inode and backref
   * only logging is done of any parent directories that are older than
   * the last committed transaction
   */
  static int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
  				  struct btrfs_inode *inode,
  				  struct dentry *parent,
  				  int inode_only,
  				  struct btrfs_log_ctx *ctx)
  {
  	struct btrfs_root *root = inode->root;
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	int ret = 0;
  	bool log_dentries = false;
  
  	if (btrfs_test_opt(fs_info, NOTREELOG)) {
  		ret = 1;
  		goto end_no_trans;
  	}
  
  	if (btrfs_root_refs(&root->root_item) == 0) {
  		ret = 1;
  		goto end_no_trans;
  	}
  
  	/*
  	 * Skip already logged inodes or inodes corresponding to tmpfiles
  	 * (since logging them is pointless, a link count of 0 means they
  	 * will never be accessible).
  	 */
  	if ((btrfs_inode_in_log(inode, trans->transid) &&
  	     list_empty(&ctx->ordered_extents)) ||
  	    inode->vfs_inode.i_nlink == 0) {
  		ret = BTRFS_NO_LOG_SYNC;
  		goto end_no_trans;
  	}
  
  	ret = start_log_trans(trans, root, ctx);
  	if (ret)
  		goto end_no_trans;
  
  	ret = btrfs_log_inode(trans, root, inode, inode_only, ctx);
  	if (ret)
  		goto end_trans;
  
  	/*
  	 * for regular files, if its inode is already on disk, we don't
  	 * have to worry about the parents at all.  This is because
  	 * we can use the last_unlink_trans field to record renames
  	 * and other fun in this file.
  	 */
  	if (S_ISREG(inode->vfs_inode.i_mode) &&
  	    inode->generation < trans->transid &&
  	    inode->last_unlink_trans < trans->transid) {
  		ret = 0;
  		goto end_trans;
  	}
  
  	if (S_ISDIR(inode->vfs_inode.i_mode) && ctx && ctx->log_new_dentries)
  		log_dentries = true;
  
  	/*
  	 * On unlink we must make sure all our current and old parent directory
  	 * inodes are fully logged. This is to prevent leaving dangling
  	 * directory index entries in directories that were our parents but are
  	 * not anymore. Not doing this results in old parent directory being
  	 * impossible to delete after log replay (rmdir will always fail with
  	 * error -ENOTEMPTY).
  	 *
  	 * Example 1:
  	 *
  	 * mkdir testdir
  	 * touch testdir/foo
  	 * ln testdir/foo testdir/bar
  	 * sync
  	 * unlink testdir/bar
  	 * xfs_io -c fsync testdir/foo
  	 * <power failure>
  	 * mount fs, triggers log replay
  	 *
  	 * If we don't log the parent directory (testdir), after log replay the
  	 * directory still has an entry pointing to the file inode using the bar
  	 * name, but a matching BTRFS_INODE_[REF|EXTREF]_KEY does not exist and
  	 * the file inode has a link count of 1.
  	 *
  	 * Example 2:
  	 *
  	 * mkdir testdir
  	 * touch foo
  	 * ln foo testdir/foo2
  	 * ln foo testdir/foo3
  	 * sync
  	 * unlink testdir/foo3
  	 * xfs_io -c fsync foo
  	 * <power failure>
  	 * mount fs, triggers log replay
  	 *
  	 * Similar as the first example, after log replay the parent directory
  	 * testdir still has an entry pointing to the inode file with name foo3
  	 * but the file inode does not have a matching BTRFS_INODE_REF_KEY item
  	 * and has a link count of 2.
  	 */
  	if (inode->last_unlink_trans >= trans->transid) {
  		ret = btrfs_log_all_parents(trans, inode, ctx);
  		if (ret)
  			goto end_trans;
  	}
  
  	ret = log_all_new_ancestors(trans, inode, parent, ctx);
  	if (ret)
  		goto end_trans;
  
  	if (log_dentries)
  		ret = log_new_dir_dentries(trans, root, inode, ctx);
  	else
  		ret = 0;
  end_trans:
  	if (ret < 0) {
  		btrfs_set_log_full_commit(trans);
  		ret = 1;
  	}
  
  	if (ret)
  		btrfs_remove_log_ctx(root, ctx);
  	btrfs_end_log_trans(root);
  end_no_trans:
  	return ret;
  }
  
  /*
   * it is not safe to log dentry if the chunk root has added new
   * chunks.  This returns 0 if the dentry was logged, and 1 otherwise.
   * If this returns 1, you must commit the transaction to safely get your
   * data on disk.
   */
  int btrfs_log_dentry_safe(struct btrfs_trans_handle *trans,
  			  struct dentry *dentry,
  			  struct btrfs_log_ctx *ctx)
  {
  	struct dentry *parent = dget_parent(dentry);
  	int ret;
  
  	ret = btrfs_log_inode_parent(trans, BTRFS_I(d_inode(dentry)), parent,
  				     LOG_INODE_ALL, ctx);
  	dput(parent);
  
  	return ret;
  }
  
  /*
   * should be called during mount to recover any replay any log trees
   * from the FS
   */
  int btrfs_recover_log_trees(struct btrfs_root *log_root_tree)
  {
  	int ret;
  	struct btrfs_path *path;
  	struct btrfs_trans_handle *trans;
  	struct btrfs_key key;
  	struct btrfs_key found_key;
  	struct btrfs_root *log;
  	struct btrfs_fs_info *fs_info = log_root_tree->fs_info;
  	struct walk_control wc = {
  		.process_func = process_one_buffer,
  		.stage = LOG_WALK_PIN_ONLY,
  	};
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	set_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags);
  
  	trans = btrfs_start_transaction(fs_info->tree_root, 0);
  	if (IS_ERR(trans)) {
  		ret = PTR_ERR(trans);
  		goto error;
  	}
  
  	wc.trans = trans;
  	wc.pin = 1;
  
  	ret = walk_log_tree(trans, log_root_tree, &wc);
  	if (ret) {
  		btrfs_handle_fs_error(fs_info, ret,
  			"Failed to pin buffers while recovering log root tree.");
  		goto error;
  	}
  
  again:
  	key.objectid = BTRFS_TREE_LOG_OBJECTID;
  	key.offset = (u64)-1;
  	key.type = BTRFS_ROOT_ITEM_KEY;
  
  	while (1) {
  		ret = btrfs_search_slot(NULL, log_root_tree, &key, path, 0, 0);
  
  		if (ret < 0) {
  			btrfs_handle_fs_error(fs_info, ret,
  				    "Couldn't find tree log root.");
  			goto error;
  		}
  		if (ret > 0) {
  			if (path->slots[0] == 0)
  				break;
  			path->slots[0]--;
  		}
  		btrfs_item_key_to_cpu(path->nodes[0], &found_key,
  				      path->slots[0]);
  		btrfs_release_path(path);
  		if (found_key.objectid != BTRFS_TREE_LOG_OBJECTID)
  			break;
  
  		log = btrfs_read_tree_root(log_root_tree, &found_key);
  		if (IS_ERR(log)) {
  			ret = PTR_ERR(log);
  			btrfs_handle_fs_error(fs_info, ret,
  				    "Couldn't read tree log root.");
  			goto error;
  		}
  
  		wc.replay_dest = btrfs_get_fs_root(fs_info, found_key.offset,
  						   true);
  		if (IS_ERR(wc.replay_dest)) {
  			ret = PTR_ERR(wc.replay_dest);
  
  			/*
  			 * We didn't find the subvol, likely because it was
  			 * deleted.  This is ok, simply skip this log and go to
  			 * the next one.
  			 *
  			 * We need to exclude the root because we can't have
  			 * other log replays overwriting this log as we'll read
  			 * it back in a few more times.  This will keep our
  			 * block from being modified, and we'll just bail for
  			 * each subsequent pass.
  			 */
  			if (ret == -ENOENT)
  				ret = btrfs_pin_extent_for_log_replay(trans,
  							log->node->start,
  							log->node->len);
  			btrfs_put_root(log);
  
  			if (!ret)
  				goto next;
  			btrfs_handle_fs_error(fs_info, ret,
  				"Couldn't read target root for tree log recovery.");
  			goto error;
  		}
  
  		wc.replay_dest->log_root = log;
  		ret = btrfs_record_root_in_trans(trans, wc.replay_dest);
  		if (ret)
  			/* The loop needs to continue due to the root refs */
  			btrfs_handle_fs_error(fs_info, ret,
  				"failed to record the log root in transaction");
  		else
  			ret = walk_log_tree(trans, log, &wc);
  
  		if (!ret && wc.stage == LOG_WALK_REPLAY_ALL) {
  			ret = fixup_inode_link_counts(trans, wc.replay_dest,
  						      path);
  		}
  
  		if (!ret && wc.stage == LOG_WALK_REPLAY_ALL) {
  			struct btrfs_root *root = wc.replay_dest;
  
  			btrfs_release_path(path);
  
  			/*
  			 * We have just replayed everything, and the highest
  			 * objectid of fs roots probably has changed in case
  			 * some inode_item's got replayed.
  			 *
  			 * root->objectid_mutex is not acquired as log replay
  			 * could only happen during mount.
  			 */
  			ret = btrfs_init_root_free_objectid(root);
  		}
  
  		wc.replay_dest->log_root = NULL;
  		btrfs_put_root(wc.replay_dest);
  		btrfs_put_root(log);
  
  		if (ret)
  			goto error;
  next:
  		if (found_key.offset == 0)
  			break;
  		key.offset = found_key.offset - 1;
  	}
  	btrfs_release_path(path);
  
  	/* step one is to pin it all, step two is to replay just inodes */
  	if (wc.pin) {
  		wc.pin = 0;
  		wc.process_func = replay_one_buffer;
  		wc.stage = LOG_WALK_REPLAY_INODES;
  		goto again;
  	}
  	/* step three is to replay everything */
  	if (wc.stage < LOG_WALK_REPLAY_ALL) {
  		wc.stage++;
  		goto again;
  	}
  
  	btrfs_free_path(path);
  
  	/* step 4: commit the transaction, which also unpins the blocks */
  	ret = btrfs_commit_transaction(trans);
  	if (ret)
  		return ret;
  
  	log_root_tree->log_root = NULL;
  	clear_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags);
  	btrfs_put_root(log_root_tree);
  
  	return 0;
  error:
  	if (wc.trans)
  		btrfs_end_transaction(wc.trans);
  	clear_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags);
  	btrfs_free_path(path);
  	return ret;
  }
  
  /*
   * there are some corner cases where we want to force a full
   * commit instead of allowing a directory to be logged.
   *
   * They revolve around files there were unlinked from the directory, and
   * this function updates the parent directory so that a full commit is
   * properly done if it is fsync'd later after the unlinks are done.
   *
   * Must be called before the unlink operations (updates to the subvolume tree,
   * inodes, etc) are done.
   */
  void btrfs_record_unlink_dir(struct btrfs_trans_handle *trans,
  			     struct btrfs_inode *dir, struct btrfs_inode *inode,
  			     int for_rename)
  {
  	/*
  	 * when we're logging a file, if it hasn't been renamed
  	 * or unlinked, and its inode is fully committed on disk,
  	 * we don't have to worry about walking up the directory chain
  	 * to log its parents.
  	 *
  	 * So, we use the last_unlink_trans field to put this transid
  	 * into the file.  When the file is logged we check it and
  	 * don't log the parents if the file is fully on disk.
  	 */
  	mutex_lock(&inode->log_mutex);
  	inode->last_unlink_trans = trans->transid;
  	mutex_unlock(&inode->log_mutex);
  
  	/*
  	 * if this directory was already logged any new
  	 * names for this file/dir will get recorded
  	 */
  	if (dir->logged_trans == trans->transid)
  		return;
  
  	/*
  	 * if the inode we're about to unlink was logged,
  	 * the log will be properly updated for any new names
  	 */
  	if (inode->logged_trans == trans->transid)
  		return;
  
  	/*
  	 * when renaming files across directories, if the directory
  	 * there we're unlinking from gets fsync'd later on, there's
  	 * no way to find the destination directory later and fsync it
  	 * properly.  So, we have to be conservative and force commits
  	 * so the new name gets discovered.
  	 */
  	if (for_rename)
  		goto record;
  
  	/* we can safely do the unlink without any special recording */
  	return;
  
  record:
  	mutex_lock(&dir->log_mutex);
  	dir->last_unlink_trans = trans->transid;
  	mutex_unlock(&dir->log_mutex);
  }
  
  /*
   * Make sure that if someone attempts to fsync the parent directory of a deleted
   * snapshot, it ends up triggering a transaction commit. This is to guarantee
   * that after replaying the log tree of the parent directory's root we will not
   * see the snapshot anymore and at log replay time we will not see any log tree
   * corresponding to the deleted snapshot's root, which could lead to replaying
   * it after replaying the log tree of the parent directory (which would replay
   * the snapshot delete operation).
   *
   * Must be called before the actual snapshot destroy operation (updates to the
   * parent root and tree of tree roots trees, etc) are done.
   */
  void btrfs_record_snapshot_destroy(struct btrfs_trans_handle *trans,
  				   struct btrfs_inode *dir)
  {
  	mutex_lock(&dir->log_mutex);
  	dir->last_unlink_trans = trans->transid;
  	mutex_unlock(&dir->log_mutex);
  }
  
  /*
   * Call this after adding a new name for a file and it will properly
   * update the log to reflect the new name.
   */
  void btrfs_log_new_name(struct btrfs_trans_handle *trans,
  			struct btrfs_inode *inode, struct btrfs_inode *old_dir,
  			struct dentry *parent)
  {
  	struct btrfs_log_ctx ctx;
  
  	/*
  	 * this will force the logging code to walk the dentry chain
  	 * up for the file
  	 */
  	if (!S_ISDIR(inode->vfs_inode.i_mode))
  		inode->last_unlink_trans = trans->transid;
  
  	/*
  	 * if this inode hasn't been logged and directory we're renaming it
  	 * from hasn't been logged, we don't need to log it
  	 */
  	if (!inode_logged(trans, inode) &&
  	    (!old_dir || !inode_logged(trans, old_dir)))
  		return;
  
  	/*
  	 * If we are doing a rename (old_dir is not NULL) from a directory that
  	 * was previously logged, make sure the next log attempt on the directory
  	 * is not skipped and logs the inode again. This is because the log may
  	 * not currently be authoritative for a range including the old
  	 * BTRFS_DIR_ITEM_KEY and BTRFS_DIR_INDEX_KEY keys, so we want to make
  	 * sure after a log replay we do not end up with both the new and old
  	 * dentries around (in case the inode is a directory we would have a
  	 * directory with two hard links and 2 inode references for different
  	 * parents). The next log attempt of old_dir will happen at
  	 * btrfs_log_all_parents(), called through btrfs_log_inode_parent()
  	 * below, because we have previously set inode->last_unlink_trans to the
  	 * current transaction ID, either here or at btrfs_record_unlink_dir() in
  	 * case inode is a directory.
  	 */
  	if (old_dir)
  		old_dir->logged_trans = 0;
  
  	btrfs_init_log_ctx(&ctx, &inode->vfs_inode);
  	ctx.logging_new_name = true;
  	/*
  	 * We don't care about the return value. If we fail to log the new name
  	 * then we know the next attempt to sync the log will fallback to a full
  	 * transaction commit (due to a call to btrfs_set_log_full_commit()), so
  	 * we don't need to worry about getting a log committed that has an
  	 * inconsistent state after a rename operation.
  	 */
  	btrfs_log_inode_parent(trans, inode, parent, LOG_INODE_EXISTS, &ctx);
  }
  
  