text: /*
   * Copyright (C) 2007 Oracle.  All rights reserved.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License v2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   */
  
  #include <linux/fs.h>
  #include <linux/slab.h>
  #include <linux/sched.h>
  #include <linux/writeback.h>
  #include <linux/pagemap.h>
  #include <linux/blkdev.h>
  #include "ctree.h"
  #include "disk-io.h"
  #include "transaction.h"
  #include "locking.h"
  #include "tree-log.h"
  
  #define BTRFS_ROOT_TRANS_TAG 0
  
  static noinline void put_transaction(struct btrfs_transaction *transaction)
  {
  	WARN_ON(transaction->use_count == 0);
  	transaction->use_count--;
  	if (transaction->use_count == 0) {
  		list_del_init(&transaction->list);
  		memset(transaction, 0, sizeof(*transaction));
  		kmem_cache_free(btrfs_transaction_cachep, transaction);
  	}
  }
  
  static noinline void switch_commit_root(struct btrfs_root *root)
  {
  	free_extent_buffer(root->commit_root);
  	root->commit_root = btrfs_root_node(root);
  }
  
  /*
   * either allocate a new transaction or hop into the existing one
   */
  static noinline int join_transaction(struct btrfs_root *root)
  {
  	struct btrfs_transaction *cur_trans;
  	cur_trans = root->fs_info->running_transaction;
  	if (!cur_trans) {
  		cur_trans = kmem_cache_alloc(btrfs_transaction_cachep,
  					     GFP_NOFS);
  		BUG_ON(!cur_trans);
  		root->fs_info->generation++;
  		cur_trans->num_writers = 1;
  		cur_trans->num_joined = 0;
  		cur_trans->transid = root->fs_info->generation;
  		init_waitqueue_head(&cur_trans->writer_wait);
  		init_waitqueue_head(&cur_trans->commit_wait);
  		cur_trans->in_commit = 0;
  		cur_trans->blocked = 0;
  		cur_trans->use_count = 1;
  		cur_trans->commit_done = 0;
  		cur_trans->start_time = get_seconds();
  
  		cur_trans->delayed_refs.root = RB_ROOT;
  		cur_trans->delayed_refs.num_entries = 0;
  		cur_trans->delayed_refs.num_heads_ready = 0;
  		cur_trans->delayed_refs.num_heads = 0;
  		cur_trans->delayed_refs.flushing = 0;
  		cur_trans->delayed_refs.run_delayed_start = 0;
  		spin_lock_init(&cur_trans->delayed_refs.lock);
  
  		INIT_LIST_HEAD(&cur_trans->pending_snapshots);
  		list_add_tail(&cur_trans->list, &root->fs_info->trans_list);
  		extent_io_tree_init(&cur_trans->dirty_pages,
  				     root->fs_info->btree_inode->i_mapping,
  				     GFP_NOFS);
  		spin_lock(&root->fs_info->new_trans_lock);
  		root->fs_info->running_transaction = cur_trans;
  		spin_unlock(&root->fs_info->new_trans_lock);
  	} else {
  		cur_trans->num_writers++;
  		cur_trans->num_joined++;
  	}
  
  	return 0;
  }
  
  /*
   * this does all the record keeping required to make sure that a reference
   * counted root is properly recorded in a given transaction.  This is required
   * to make sure the old root from before we joined the transaction is deleted
   * when the transaction commits
   */
  static noinline int record_root_in_trans(struct btrfs_trans_handle *trans,
  					 struct btrfs_root *root)
  {
  	if (root->ref_cows && root->last_trans < trans->transid) {
  		WARN_ON(root == root->fs_info->extent_root);
  		WARN_ON(root->commit_root != root->node);
  
  		radix_tree_tag_set(&root->fs_info->fs_roots_radix,
  			   (unsigned long)root->root_key.objectid,
  			   BTRFS_ROOT_TRANS_TAG);
  		root->last_trans = trans->transid;
  		btrfs_init_reloc_root(trans, root);
  	}
  	return 0;
  }
  
  int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
  			       struct btrfs_root *root)
  {
  	if (!root->ref_cows)
  		return 0;
  
  	mutex_lock(&root->fs_info->trans_mutex);
  	if (root->last_trans == trans->transid) {
  		mutex_unlock(&root->fs_info->trans_mutex);
  		return 0;
  	}
  
  	record_root_in_trans(trans, root);
  	mutex_unlock(&root->fs_info->trans_mutex);
  	return 0;
  }
  
  /* wait for commit against the current transaction to become unblocked
   * when this is done, it is safe to start a new transaction, but the current
   * transaction might not be fully on disk.
   */
  static void wait_current_trans(struct btrfs_root *root)
  {
  	struct btrfs_transaction *cur_trans;
  
  	cur_trans = root->fs_info->running_transaction;
  	if (cur_trans && cur_trans->blocked) {
  		DEFINE_WAIT(wait);
  		cur_trans->use_count++;
  		while (1) {
  			prepare_to_wait(&root->fs_info->transaction_wait, &wait,
  					TASK_UNINTERRUPTIBLE);
  			if (!cur_trans->blocked)
  				break;
  			mutex_unlock(&root->fs_info->trans_mutex);
  			schedule();
  			mutex_lock(&root->fs_info->trans_mutex);
  		}
  		finish_wait(&root->fs_info->transaction_wait, &wait);
  		put_transaction(cur_trans);
  	}
  }
  
  enum btrfs_trans_type {
  	TRANS_START,
  	TRANS_JOIN,
  	TRANS_USERSPACE,
  };
  
  static int may_wait_transaction(struct btrfs_root *root, int type)
  {
  	if (!root->fs_info->log_root_recovering &&
  	    ((type == TRANS_START && !root->fs_info->open_ioctl_trans) ||
  	     type == TRANS_USERSPACE))
  		return 1;
  	return 0;
  }
  
  static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
  						    u64 num_items, int type)
  {
  	struct btrfs_trans_handle *h;
  	struct btrfs_transaction *cur_trans;
  	int retries = 0;
  	int ret;
  again:
  	h = kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
  	if (!h)
  		return ERR_PTR(-ENOMEM);
  
  	mutex_lock(&root->fs_info->trans_mutex);
  	if (may_wait_transaction(root, type))
  		wait_current_trans(root);
  
  	ret = join_transaction(root);
  	BUG_ON(ret);
  
  	cur_trans = root->fs_info->running_transaction;
  	cur_trans->use_count++;
  	mutex_unlock(&root->fs_info->trans_mutex);
  
  	h->transid = cur_trans->transid;
  	h->transaction = cur_trans;
  	h->blocks_used = 0;
  	h->block_group = 0;
  	h->bytes_reserved = 0;
  	h->delayed_ref_updates = 0;
  	h->block_rsv = NULL;
  
  	smp_mb();
  	if (cur_trans->blocked && may_wait_transaction(root, type)) {
  		btrfs_commit_transaction(h, root);
  		goto again;
  	}
  
  	if (num_items > 0) {
  		ret = btrfs_trans_reserve_metadata(h, root, num_items,
  						   &retries);
  		if (ret == -EAGAIN) {
  			btrfs_commit_transaction(h, root);
  			goto again;
  		}
  		if (ret < 0) {
  			btrfs_end_transaction(h, root);
  			return ERR_PTR(ret);
  		}
  	}
  
  	mutex_lock(&root->fs_info->trans_mutex);
  	record_root_in_trans(h, root);
  	mutex_unlock(&root->fs_info->trans_mutex);
  
  	if (!current->journal_info && type != TRANS_USERSPACE)
  		current->journal_info = h;
  	return h;
  }
  
  struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
  						   int num_items)
  {
  	return start_transaction(root, num_items, TRANS_START);
  }
  struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root,
  						   int num_blocks)
  {
  	return start_transaction(root, 0, TRANS_JOIN);
  }
  
  struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *r,
  							 int num_blocks)
  {
  	return start_transaction(r, 0, TRANS_USERSPACE);
  }
  
  /* wait for a transaction commit to be fully complete */
  static noinline int wait_for_commit(struct btrfs_root *root,
  				    struct btrfs_transaction *commit)
  {
  	DEFINE_WAIT(wait);
  	mutex_lock(&root->fs_info->trans_mutex);
  	while (!commit->commit_done) {
  		prepare_to_wait(&commit->commit_wait, &wait,
  				TASK_UNINTERRUPTIBLE);
  		if (commit->commit_done)
  			break;
  		mutex_unlock(&root->fs_info->trans_mutex);
  		schedule();
  		mutex_lock(&root->fs_info->trans_mutex);
  	}
  	mutex_unlock(&root->fs_info->trans_mutex);
  	finish_wait(&commit->commit_wait, &wait);
  	return 0;
  }
  
  #if 0
  /*
   * rate limit against the drop_snapshot code.  This helps to slow down new
   * operations if the drop_snapshot code isn't able to keep up.
   */
  static void throttle_on_drops(struct btrfs_root *root)
  {
  	struct btrfs_fs_info *info = root->fs_info;
  	int harder_count = 0;
  
  harder:
  	if (atomic_read(&info->throttles)) {
  		DEFINE_WAIT(wait);
  		int thr;
  		thr = atomic_read(&info->throttle_gen);
  
  		do {
  			prepare_to_wait(&info->transaction_throttle,
  					&wait, TASK_UNINTERRUPTIBLE);
  			if (!atomic_read(&info->throttles)) {
  				finish_wait(&info->transaction_throttle, &wait);
  				break;
  			}
  			schedule();
  			finish_wait(&info->transaction_throttle, &wait);
  		} while (thr == atomic_read(&info->throttle_gen));
  		harder_count++;
  
  		if (root->fs_info->total_ref_cache_size > 1 * 1024 * 1024 &&
  		    harder_count < 2)
  			goto harder;
  
  		if (root->fs_info->total_ref_cache_size > 5 * 1024 * 1024 &&
  		    harder_count < 10)
  			goto harder;
  
  		if (root->fs_info->total_ref_cache_size > 10 * 1024 * 1024 &&
  		    harder_count < 20)
  			goto harder;
  	}
  }
  #endif
  
  void btrfs_throttle(struct btrfs_root *root)
  {
  	mutex_lock(&root->fs_info->trans_mutex);
  	if (!root->fs_info->open_ioctl_trans)
  		wait_current_trans(root);
  	mutex_unlock(&root->fs_info->trans_mutex);
  }
  
  static int should_end_transaction(struct btrfs_trans_handle *trans,
  				  struct btrfs_root *root)
  {
  	int ret;
  	ret = btrfs_block_rsv_check(trans, root,
  				    &root->fs_info->global_block_rsv, 0, 5);
  	return ret ? 1 : 0;
  }
  
  int btrfs_should_end_transaction(struct btrfs_trans_handle *trans,
  				 struct btrfs_root *root)
  {
  	struct btrfs_transaction *cur_trans = trans->transaction;
  	int updates;
  
  	if (cur_trans->blocked || cur_trans->delayed_refs.flushing)
  		return 1;
  
  	updates = trans->delayed_ref_updates;
  	trans->delayed_ref_updates = 0;
  	if (updates)
  		btrfs_run_delayed_refs(trans, root, updates);
  
  	return should_end_transaction(trans, root);
  }
  
  static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
  			  struct btrfs_root *root, int throttle)
  {
  	struct btrfs_transaction *cur_trans = trans->transaction;
  	struct btrfs_fs_info *info = root->fs_info;
  	int count = 0;
  
  	while (count < 4) {
  		unsigned long cur = trans->delayed_ref_updates;
  		trans->delayed_ref_updates = 0;
  		if (cur &&
  		    trans->transaction->delayed_refs.num_heads_ready > 64) {
  			trans->delayed_ref_updates = 0;
  
  			/*
  			 * do a full flush if the transaction is trying
  			 * to close
  			 */
  			if (trans->transaction->delayed_refs.flushing)
  				cur = 0;
  			btrfs_run_delayed_refs(trans, root, cur);
  		} else {
  			break;
  		}
  		count++;
  	}
  
  	btrfs_trans_release_metadata(trans, root);
  
  	if (!root->fs_info->open_ioctl_trans &&
  	    should_end_transaction(trans, root))
  		trans->transaction->blocked = 1;
  
  	if (cur_trans->blocked && !cur_trans->in_commit) {
  		if (throttle)
  			return btrfs_commit_transaction(trans, root);
  		else
  			wake_up_process(info->transaction_kthread);
  	}
  
  	mutex_lock(&info->trans_mutex);
  	WARN_ON(cur_trans != info->running_transaction);
  	WARN_ON(cur_trans->num_writers < 1);
  	cur_trans->num_writers--;
  
  	if (waitqueue_active(&cur_trans->writer_wait))
  		wake_up(&cur_trans->writer_wait);
  	put_transaction(cur_trans);
  	mutex_unlock(&info->trans_mutex);
  
  	if (current->journal_info == trans)
  		current->journal_info = NULL;
  	memset(trans, 0, sizeof(*trans));
  	kmem_cache_free(btrfs_trans_handle_cachep, trans);
  
  	if (throttle)
  		btrfs_run_delayed_iputs(root);
  
  	return 0;
  }
  
  int btrfs_end_transaction(struct btrfs_trans_handle *trans,
  			  struct btrfs_root *root)
  {
  	return __btrfs_end_transaction(trans, root, 0);
  }
  
  int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
  				   struct btrfs_root *root)
  {
  	return __btrfs_end_transaction(trans, root, 1);
  }
  
  /*
   * when btree blocks are allocated, they have some corresponding bits set for
   * them in one of two extent_io trees.  This is used to make sure all of
   * those extents are sent to disk but does not wait on them
   */
  int btrfs_write_marked_extents(struct btrfs_root *root,
  			       struct extent_io_tree *dirty_pages, int mark)
  {
  	int ret;
  	int err = 0;
  	int werr = 0;
  	struct page *page;
  	struct inode *btree_inode = root->fs_info->btree_inode;
  	u64 start = 0;
  	u64 end;
  	unsigned long index;
  
  	while (1) {
  		ret = find_first_extent_bit(dirty_pages, start, &start, &end,
  					    mark);
  		if (ret)
  			break;
  		while (start <= end) {
  			cond_resched();
  
  			index = start >> PAGE_CACHE_SHIFT;
  			start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
  			page = find_get_page(btree_inode->i_mapping, index);
  			if (!page)
  				continue;
  
  			btree_lock_page_hook(page);
  			if (!page->mapping) {
  				unlock_page(page);
  				page_cache_release(page);
  				continue;
  			}
  
  			if (PageWriteback(page)) {
  				if (PageDirty(page))
  					wait_on_page_writeback(page);
  				else {
  					unlock_page(page);
  					page_cache_release(page);
  					continue;
  				}
  			}
  			err = write_one_page(page, 0);
  			if (err)
  				werr = err;
  			page_cache_release(page);
  		}
  	}
  	if (err)
  		werr = err;
  	return werr;
  }
  
  /*
   * when btree blocks are allocated, they have some corresponding bits set for
   * them in one of two extent_io trees.  This is used to make sure all of
   * those extents are on disk for transaction or log commit.  We wait
   * on all the pages and clear them from the dirty pages state tree
   */
  int btrfs_wait_marked_extents(struct btrfs_root *root,
  			      struct extent_io_tree *dirty_pages, int mark)
  {
  	int ret;
  	int err = 0;
  	int werr = 0;
  	struct page *page;
  	struct inode *btree_inode = root->fs_info->btree_inode;
  	u64 start = 0;
  	u64 end;
  	unsigned long index;
  
  	while (1) {
  		ret = find_first_extent_bit(dirty_pages, start, &start, &end,
  					    mark);
  		if (ret)
  			break;
  
  		clear_extent_bits(dirty_pages, start, end, mark, GFP_NOFS);
  		while (start <= end) {
  			index = start >> PAGE_CACHE_SHIFT;
  			start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
  			page = find_get_page(btree_inode->i_mapping, index);
  			if (!page)
  				continue;
  			if (PageDirty(page)) {
  				btree_lock_page_hook(page);
  				wait_on_page_writeback(page);
  				err = write_one_page(page, 0);
  				if (err)
  					werr = err;
  			}
  			wait_on_page_writeback(page);
  			page_cache_release(page);
  			cond_resched();
  		}
  	}
  	if (err)
  		werr = err;
  	return werr;
  }
  
  /*
   * when btree blocks are allocated, they have some corresponding bits set for
   * them in one of two extent_io trees.  This is used to make sure all of
   * those extents are on disk for transaction or log commit
   */
  int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
  				struct extent_io_tree *dirty_pages, int mark)
  {
  	int ret;
  	int ret2;
  
  	ret = btrfs_write_marked_extents(root, dirty_pages, mark);
  	ret2 = btrfs_wait_marked_extents(root, dirty_pages, mark);
  	return ret || ret2;
  }
  
  int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
  				     struct btrfs_root *root)
  {
  	if (!trans || !trans->transaction) {
  		struct inode *btree_inode;
  		btree_inode = root->fs_info->btree_inode;
  		return filemap_write_and_wait(btree_inode->i_mapping);
  	}
  	return btrfs_write_and_wait_marked_extents(root,
  					   &trans->transaction->dirty_pages,
  					   EXTENT_DIRTY);
  }
  
  /*
   * this is used to update the root pointer in the tree of tree roots.
   *
   * But, in the case of the extent allocation tree, updating the root
   * pointer may allocate blocks which may change the root of the extent
   * allocation tree.
   *
   * So, this loops and repeats and makes sure the cowonly root didn't
   * change while the root pointer was being updated in the metadata.
   */
  static int update_cowonly_root(struct btrfs_trans_handle *trans,
  			       struct btrfs_root *root)
  {
  	int ret;
  	u64 old_root_bytenr;
  	u64 old_root_used;
  	struct btrfs_root *tree_root = root->fs_info->tree_root;
  
  	old_root_used = btrfs_root_used(&root->root_item);
  	btrfs_write_dirty_block_groups(trans, root);
  
  	while (1) {
  		old_root_bytenr = btrfs_root_bytenr(&root->root_item);
  		if (old_root_bytenr == root->node->start &&
  		    old_root_used == btrfs_root_used(&root->root_item))
  			break;
  
  		btrfs_set_root_node(&root->root_item, root->node);
  		ret = btrfs_update_root(trans, tree_root,
  					&root->root_key,
  					&root->root_item);
  		BUG_ON(ret);
  
  		old_root_used = btrfs_root_used(&root->root_item);
  		ret = btrfs_write_dirty_block_groups(trans, root);
  		BUG_ON(ret);
  	}
  
  	if (root != root->fs_info->extent_root)
  		switch_commit_root(root);
  
  	return 0;
  }
  
  /*
   * update all the cowonly tree roots on disk
   */
  static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
  					 struct btrfs_root *root)
  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	struct list_head *next;
  	struct extent_buffer *eb;
  	int ret;
  
  	ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
  	BUG_ON(ret);
  
  	eb = btrfs_lock_root_node(fs_info->tree_root);
  	btrfs_cow_block(trans, fs_info->tree_root, eb, NULL, 0, &eb);
  	btrfs_tree_unlock(eb);
  	free_extent_buffer(eb);
  
  	ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
  	BUG_ON(ret);
  
  	while (!list_empty(&fs_info->dirty_cowonly_roots)) {
  		next = fs_info->dirty_cowonly_roots.next;
  		list_del_init(next);
  		root = list_entry(next, struct btrfs_root, dirty_list);
  
  		update_cowonly_root(trans, root);
  	}
  
  	down_write(&fs_info->extent_commit_sem);
  	switch_commit_root(fs_info->extent_root);
  	up_write(&fs_info->extent_commit_sem);
  
  	return 0;
  }
  
  /*
   * dead roots are old snapshots that need to be deleted.  This allocates
   * a dirty root struct and adds it into the list of dead roots that need to
   * be deleted
   */
  int btrfs_add_dead_root(struct btrfs_root *root)
  {
  	mutex_lock(&root->fs_info->trans_mutex);
  	list_add(&root->root_list, &root->fs_info->dead_roots);
  	mutex_unlock(&root->fs_info->trans_mutex);
  	return 0;
  }
  
  /*
   * update all the cowonly tree roots on disk
   */
  static noinline int commit_fs_roots(struct btrfs_trans_handle *trans,
  				    struct btrfs_root *root)
  {
  	struct btrfs_root *gang[8];
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	int i;
  	int ret;
  	int err = 0;
  
  	while (1) {
  		ret = radix_tree_gang_lookup_tag(&fs_info->fs_roots_radix,
  						 (void **)gang, 0,
  						 ARRAY_SIZE(gang),
  						 BTRFS_ROOT_TRANS_TAG);
  		if (ret == 0)
  			break;
  		for (i = 0; i < ret; i++) {
  			root = gang[i];
  			radix_tree_tag_clear(&fs_info->fs_roots_radix,
  					(unsigned long)root->root_key.objectid,
  					BTRFS_ROOT_TRANS_TAG);
  
  			btrfs_free_log(trans, root);
  			btrfs_update_reloc_root(trans, root);
  			btrfs_orphan_commit_root(trans, root);
  
  			if (root->commit_root != root->node) {
  				switch_commit_root(root);
  				btrfs_set_root_node(&root->root_item,
  						    root->node);
  			}
  
  			err = btrfs_update_root(trans, fs_info->tree_root,
  						&root->root_key,
  						&root->root_item);
  			if (err)
  				break;
  		}
  	}
  	return err;
  }
  
  /*
   * defrag a given btree.  If cacheonly == 1, this won't read from the disk,
   * otherwise every leaf in the btree is read and defragged.
   */
  int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
  {
  	struct btrfs_fs_info *info = root->fs_info;
  	struct btrfs_trans_handle *trans;
  	int ret;
  	unsigned long nr;
  
  	if (xchg(&root->defrag_running, 1))
  		return 0;
  
  	while (1) {
  		trans = btrfs_start_transaction(root, 0);
  		if (IS_ERR(trans))
  			return PTR_ERR(trans);
  
  		ret = btrfs_defrag_leaves(trans, root, cacheonly);
  
  		nr = trans->blocks_used;
  		btrfs_end_transaction(trans, root);
  		btrfs_btree_balance_dirty(info->tree_root, nr);
  		cond_resched();
  
  		if (root->fs_info->closing || ret != -EAGAIN)
  			break;
  	}
  	root->defrag_running = 0;
  	return ret;
  }
  
  #if 0
  /*
   * when dropping snapshots, we generate a ton of delayed refs, and it makes
   * sense not to join the transaction while it is trying to flush the current
   * queue of delayed refs out.
   *
   * This is used by the drop snapshot code only
   */
  static noinline int wait_transaction_pre_flush(struct btrfs_fs_info *info)
  {
  	DEFINE_WAIT(wait);
  
  	mutex_lock(&info->trans_mutex);
  	while (info->running_transaction &&
  	       info->running_transaction->delayed_refs.flushing) {
  		prepare_to_wait(&info->transaction_wait, &wait,
  				TASK_UNINTERRUPTIBLE);
  		mutex_unlock(&info->trans_mutex);
  
  		schedule();
  
  		mutex_lock(&info->trans_mutex);
  		finish_wait(&info->transaction_wait, &wait);
  	}
  	mutex_unlock(&info->trans_mutex);
  	return 0;
  }
  
  /*
   * Given a list of roots that need to be deleted, call btrfs_drop_snapshot on
   * all of them
   */
  int btrfs_drop_dead_root(struct btrfs_root *root)
  {
  	struct btrfs_trans_handle *trans;
  	struct btrfs_root *tree_root = root->fs_info->tree_root;
  	unsigned long nr;
  	int ret;
  
  	while (1) {
  		/*
  		 * we don't want to jump in and create a bunch of
  		 * delayed refs if the transaction is starting to close
  		 */
  		wait_transaction_pre_flush(tree_root->fs_info);
  		trans = btrfs_start_transaction(tree_root, 1);
  
  		/*
  		 * we've joined a transaction, make sure it isn't
  		 * closing right now
  		 */
  		if (trans->transaction->delayed_refs.flushing) {
  			btrfs_end_transaction(trans, tree_root);
  			continue;
  		}
  
  		ret = btrfs_drop_snapshot(trans, root);
  		if (ret != -EAGAIN)
  			break;
  
  		ret = btrfs_update_root(trans, tree_root,
  					&root->root_key,
  					&root->root_item);
  		if (ret)
  			break;
  
  		nr = trans->blocks_used;
  		ret = btrfs_end_transaction(trans, tree_root);
  		BUG_ON(ret);
  
  		btrfs_btree_balance_dirty(tree_root, nr);
  		cond_resched();
  	}
  	BUG_ON(ret);
  
  	ret = btrfs_del_root(trans, tree_root, &root->root_key);
  	BUG_ON(ret);
  
  	nr = trans->blocks_used;
  	ret = btrfs_end_transaction(trans, tree_root);
  	BUG_ON(ret);
  
  	free_extent_buffer(root->node);
  	free_extent_buffer(root->commit_root);
  	kfree(root);
  
  	btrfs_btree_balance_dirty(tree_root, nr);
  	return ret;
  }
  #endif
  
  /*
   * new snapshots need to be created at a very specific time in the
   * transaction commit.  This does the actual creation
   */
  static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
  				   struct btrfs_fs_info *fs_info,
  				   struct btrfs_pending_snapshot *pending)
  {
  	struct btrfs_key key;
  	struct btrfs_root_item *new_root_item;
  	struct btrfs_root *tree_root = fs_info->tree_root;
  	struct btrfs_root *root = pending->root;
  	struct btrfs_root *parent_root;
  	struct inode *parent_inode;
  	struct dentry *dentry;
  	struct extent_buffer *tmp;
  	struct extent_buffer *old;
  	int ret;
  	int retries = 0;
  	u64 to_reserve = 0;
  	u64 index = 0;
  	u64 objectid;
  
  	new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
  	if (!new_root_item) {
  		pending->error = -ENOMEM;
  		goto fail;
  	}
  
  	ret = btrfs_find_free_objectid(trans, tree_root, 0, &objectid);
  	if (ret) {
  		pending->error = ret;
  		goto fail;
  	}
  
  	btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);
  	btrfs_orphan_pre_snapshot(trans, pending, &to_reserve);
  
  	if (to_reserve > 0) {
  		ret = btrfs_block_rsv_add(trans, root, &pending->block_rsv,
  					  to_reserve, &retries);
  		if (ret) {
  			pending->error = ret;
  			goto fail;
  		}
  	}
  
  	key.objectid = objectid;
  	key.offset = (u64)-1;
  	key.type = BTRFS_ROOT_ITEM_KEY;
  
  	trans->block_rsv = &pending->block_rsv;
  
  	dentry = pending->dentry;
  	parent_inode = dentry->d_parent->d_inode;
  	parent_root = BTRFS_I(parent_inode)->root;
  	record_root_in_trans(trans, parent_root);
  
  	/*
  	 * insert the directory item
  	 */
  	ret = btrfs_set_inode_index(parent_inode, &index);
  	BUG_ON(ret);
  	ret = btrfs_insert_dir_item(trans, parent_root,
  				dentry->d_name.name, dentry->d_name.len,
  				parent_inode->i_ino, &key,
  				BTRFS_FT_DIR, index);
  	BUG_ON(ret);
  
  	btrfs_i_size_write(parent_inode, parent_inode->i_size +
  					 dentry->d_name.len * 2);
  	ret = btrfs_update_inode(trans, parent_root, parent_inode);
  	BUG_ON(ret);
  
  	record_root_in_trans(trans, root);
  	btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
  	memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
  
  	old = btrfs_lock_root_node(root);
  	btrfs_cow_block(trans, root, old, NULL, 0, &old);
  	btrfs_set_lock_blocking(old);
  
  	btrfs_copy_root(trans, root, old, &tmp, objectid);
  	btrfs_tree_unlock(old);
  	free_extent_buffer(old);
  
  	btrfs_set_root_node(new_root_item, tmp);
  	/* record when the snapshot was created in key.offset */
  	key.offset = trans->transid;
  	ret = btrfs_insert_root(trans, tree_root, &key, new_root_item);
  	btrfs_tree_unlock(tmp);
  	free_extent_buffer(tmp);
  	BUG_ON(ret);
  
  	/*
  	 * insert root back/forward references
  	 */
  	ret = btrfs_add_root_ref(trans, tree_root, objectid,
  				 parent_root->root_key.objectid,
  				 parent_inode->i_ino, index,
  				 dentry->d_name.name, dentry->d_name.len);
  	BUG_ON(ret);
  
  	key.offset = (u64)-1;
  	pending->snap = btrfs_read_fs_root_no_name(root->fs_info, &key);
  	BUG_ON(IS_ERR(pending->snap));
  
  	btrfs_reloc_post_snapshot(trans, pending);
  	btrfs_orphan_post_snapshot(trans, pending);
  fail:
  	kfree(new_root_item);
  	btrfs_block_rsv_release(root, &pending->block_rsv, (u64)-1);
  	return 0;
  }
  
  /*
   * create all the snapshots we've scheduled for creation
   */
  static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans,
  					     struct btrfs_fs_info *fs_info)
  {
  	struct btrfs_pending_snapshot *pending;
  	struct list_head *head = &trans->transaction->pending_snapshots;
  	int ret;
  
  	list_for_each_entry(pending, head, list) {
  		ret = create_pending_snapshot(trans, fs_info, pending);
  		BUG_ON(ret);
  	}
  	return 0;
  }
  
  static void update_super_roots(struct btrfs_root *root)
  {
  	struct btrfs_root_item *root_item;
  	struct btrfs_super_block *super;
  
  	super = &root->fs_info->super_copy;
  
  	root_item = &root->fs_info->chunk_root->root_item;
  	super->chunk_root = root_item->bytenr;
  	super->chunk_root_generation = root_item->generation;
  	super->chunk_root_level = root_item->level;
  
  	root_item = &root->fs_info->tree_root->root_item;
  	super->root = root_item->bytenr;
  	super->generation = root_item->generation;
  	super->root_level = root_item->level;
  }
  
  int btrfs_transaction_in_commit(struct btrfs_fs_info *info)
  {
  	int ret = 0;
  	spin_lock(&info->new_trans_lock);
  	if (info->running_transaction)
  		ret = info->running_transaction->in_commit;
  	spin_unlock(&info->new_trans_lock);
  	return ret;
  }
  
  int btrfs_transaction_blocked(struct btrfs_fs_info *info)
  {
  	int ret = 0;
  	spin_lock(&info->new_trans_lock);
  	if (info->running_transaction)
  		ret = info->running_transaction->blocked;
  	spin_unlock(&info->new_trans_lock);
  	return ret;
  }
  
  int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
  			     struct btrfs_root *root)
  {
  	unsigned long joined = 0;
  	unsigned long timeout = 1;
  	struct btrfs_transaction *cur_trans;
  	struct btrfs_transaction *prev_trans = NULL;
  	DEFINE_WAIT(wait);
  	int ret;
  	int should_grow = 0;
  	unsigned long now = get_seconds();
  	int flush_on_commit = btrfs_test_opt(root, FLUSHONCOMMIT);
  
  	btrfs_run_ordered_operations(root, 0);
  
  	/* make a pass through all the delayed refs we have so far
  	 * any runnings procs may add more while we are here
  	 */
  	ret = btrfs_run_delayed_refs(trans, root, 0);
  	BUG_ON(ret);
  
  	btrfs_trans_release_metadata(trans, root);
  
  	cur_trans = trans->transaction;
  	/*
  	 * set the flushing flag so procs in this transaction have to
  	 * start sending their work down.
  	 */
  	cur_trans->delayed_refs.flushing = 1;
  
  	ret = btrfs_run_delayed_refs(trans, root, 0);
  	BUG_ON(ret);
  
  	mutex_lock(&root->fs_info->trans_mutex);
  	if (cur_trans->in_commit) {
  		cur_trans->use_count++;
  		mutex_unlock(&root->fs_info->trans_mutex);
  		btrfs_end_transaction(trans, root);
  
  		ret = wait_for_commit(root, cur_trans);
  		BUG_ON(ret);
  
  		mutex_lock(&root->fs_info->trans_mutex);
  		put_transaction(cur_trans);
  		mutex_unlock(&root->fs_info->trans_mutex);
  
  		return 0;
  	}
  
  	trans->transaction->in_commit = 1;
  	trans->transaction->blocked = 1;
  	if (cur_trans->list.prev != &root->fs_info->trans_list) {
  		prev_trans = list_entry(cur_trans->list.prev,
  					struct btrfs_transaction, list);
  		if (!prev_trans->commit_done) {
  			prev_trans->use_count++;
  			mutex_unlock(&root->fs_info->trans_mutex);
  
  			wait_for_commit(root, prev_trans);
  
  			mutex_lock(&root->fs_info->trans_mutex);
  			put_transaction(prev_trans);
  		}
  	}
  
  	if (now < cur_trans->start_time || now - cur_trans->start_time < 1)
  		should_grow = 1;
  
  	do {
  		int snap_pending = 0;
  		joined = cur_trans->num_joined;
  		if (!list_empty(&trans->transaction->pending_snapshots))
  			snap_pending = 1;
  
  		WARN_ON(cur_trans != trans->transaction);
  		if (cur_trans->num_writers > 1)
  			timeout = MAX_SCHEDULE_TIMEOUT;
  		else if (should_grow)
  			timeout = 1;
  
  		mutex_unlock(&root->fs_info->trans_mutex);
  
  		if (flush_on_commit || snap_pending) {
  			btrfs_start_delalloc_inodes(root, 1);
  			ret = btrfs_wait_ordered_extents(root, 0, 1);
  			BUG_ON(ret);
  		}
  
  		/*
  		 * rename don't use btrfs_join_transaction, so, once we
  		 * set the transaction to blocked above, we aren't going
  		 * to get any new ordered operations.  We can safely run
  		 * it here and no for sure that nothing new will be added
  		 * to the list
  		 */
  		btrfs_run_ordered_operations(root, 1);
  
  		prepare_to_wait(&cur_trans->writer_wait, &wait,
  				TASK_UNINTERRUPTIBLE);
  
  		smp_mb();
  		if (cur_trans->num_writers > 1 || should_grow)
  			schedule_timeout(timeout);
  
  		mutex_lock(&root->fs_info->trans_mutex);
  		finish_wait(&cur_trans->writer_wait, &wait);
  	} while (cur_trans->num_writers > 1 ||
  		 (should_grow && cur_trans->num_joined != joined));
  
  	ret = create_pending_snapshots(trans, root->fs_info);
  	BUG_ON(ret);
  
  	ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
  	BUG_ON(ret);
  
  	WARN_ON(cur_trans != trans->transaction);
  
  	/* btrfs_commit_tree_roots is responsible for getting the
  	 * various roots consistent with each other.  Every pointer
  	 * in the tree of tree roots has to point to the most up to date
  	 * root for every subvolume and other tree.  So, we have to keep
  	 * the tree logging code from jumping in and changing any
  	 * of the trees.
  	 *
  	 * At this point in the commit, there can't be any tree-log
  	 * writers, but a little lower down we drop the trans mutex
  	 * and let new people in.  By holding the tree_log_mutex
  	 * from now until after the super is written, we avoid races
  	 * with the tree-log code.
  	 */
  	mutex_lock(&root->fs_info->tree_log_mutex);
  
  	ret = commit_fs_roots(trans, root);
  	BUG_ON(ret);
  
  	/* commit_fs_roots gets rid of all the tree log roots, it is now
  	 * safe to free the root of tree log roots
  	 */
  	btrfs_free_log_root_tree(trans, root->fs_info);
  
  	ret = commit_cowonly_roots(trans, root);
  	BUG_ON(ret);
  
  	btrfs_prepare_extent_commit(trans, root);
  
  	cur_trans = root->fs_info->running_transaction;
  	spin_lock(&root->fs_info->new_trans_lock);
  	root->fs_info->running_transaction = NULL;
  	spin_unlock(&root->fs_info->new_trans_lock);
  
  	btrfs_set_root_node(&root->fs_info->tree_root->root_item,
  			    root->fs_info->tree_root->node);
  	switch_commit_root(root->fs_info->tree_root);
  
  	btrfs_set_root_node(&root->fs_info->chunk_root->root_item,
  			    root->fs_info->chunk_root->node);
  	switch_commit_root(root->fs_info->chunk_root);
  
  	update_super_roots(root);
  
  	if (!root->fs_info->log_root_recovering) {
  		btrfs_set_super_log_root(&root->fs_info->super_copy, 0);
  		btrfs_set_super_log_root_level(&root->fs_info->super_copy, 0);
  	}
  
  	memcpy(&root->fs_info->super_for_commit, &root->fs_info->super_copy,
  	       sizeof(root->fs_info->super_copy));
  
  	trans->transaction->blocked = 0;
  
  	wake_up(&root->fs_info->transaction_wait);
  
  	mutex_unlock(&root->fs_info->trans_mutex);
  	ret = btrfs_write_and_wait_transaction(trans, root);
  	BUG_ON(ret);
  	write_ctree_super(trans, root, 0);
  
  	/*
  	 * the super is written, we can safely allow the tree-loggers
  	 * to go about their business
  	 */
  	mutex_unlock(&root->fs_info->tree_log_mutex);
  
  	btrfs_finish_extent_commit(trans, root);
  
  	mutex_lock(&root->fs_info->trans_mutex);
  
  	cur_trans->commit_done = 1;
  
  	root->fs_info->last_trans_committed = cur_trans->transid;
  
  	wake_up(&cur_trans->commit_wait);
  
  	put_transaction(cur_trans);
  	put_transaction(cur_trans);
  
  	mutex_unlock(&root->fs_info->trans_mutex);
  
  	if (current->journal_info == trans)
  		current->journal_info = NULL;
  
  	kmem_cache_free(btrfs_trans_handle_cachep, trans);
  
  	if (current != root->fs_info->transaction_kthread)
  		btrfs_run_delayed_iputs(root);
  
  	return ret;
  }
  
  /*
   * interface function to delete all the snapshots we have scheduled for deletion
   */
  int btrfs_clean_old_snapshots(struct btrfs_root *root)
  {
  	LIST_HEAD(list);
  	struct btrfs_fs_info *fs_info = root->fs_info;
  
  	mutex_lock(&fs_info->trans_mutex);
  	list_splice_init(&fs_info->dead_roots, &list);
  	mutex_unlock(&fs_info->trans_mutex);
  
  	while (!list_empty(&list)) {
  		root = list_entry(list.next, struct btrfs_root, root_list);
  		list_del(&root->root_list);
  
  		if (btrfs_header_backref_rev(root->node) <
  		    BTRFS_MIXED_BACKREF_REV)
  			btrfs_drop_snapshot(root, NULL, 0);
  		else
  			btrfs_drop_snapshot(root, NULL, 1);
  	}
  	return 0;
  }
  