text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Copyright (C) 2007 Oracle.  All rights reserved.
   */
  
  #include <linux/err.h>
  #include <linux/uuid.h>
  #include "ctree.h"
  #include "transaction.h"
  #include "disk-io.h"
  #include "print-tree.h"
  #include "qgroup.h"
  #include "space-info.h"
  
  /*
   * Read a root item from the tree. In case we detect a root item smaller then
   * sizeof(root_item), we know it's an old version of the root structure and
   * initialize all new fields to zero. The same happens if we detect mismatching
   * generation numbers as then we know the root was once mounted with an older
   * kernel that was not aware of the root item structure change.
   */
  static void btrfs_read_root_item(struct extent_buffer *eb, int slot,
  				struct btrfs_root_item *item)
  {
  	u32 len;
  	int need_reset = 0;
  
  	len = btrfs_item_size_nr(eb, slot);
  	read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
  			   min_t(u32, len, sizeof(*item)));
  	if (len < sizeof(*item))
  		need_reset = 1;
  	if (!need_reset && btrfs_root_generation(item)
  		!= btrfs_root_generation_v2(item)) {
  		if (btrfs_root_generation_v2(item) != 0) {
  			btrfs_warn(eb->fs_info,
  					"mismatching generation and generation_v2 found in root item. This root was probably mounted with an older kernel. Resetting all new fields.");
  		}
  		need_reset = 1;
  	}
  	if (need_reset) {
  		memset(&item->generation_v2, 0,
  			sizeof(*item) - offsetof(struct btrfs_root_item,
  					generation_v2));
  
  		generate_random_guid(item->uuid);
  	}
  }
  
  /*
   * btrfs_find_root - lookup the root by the key.
   * root: the root of the root tree
   * search_key: the key to search
   * path: the path we search
   * root_item: the root item of the tree we look for
   * root_key: the root key of the tree we look for
   *
   * If ->offset of 'search_key' is -1ULL, it means we are not sure the offset
   * of the search key, just lookup the root with the highest offset for a
   * given objectid.
   *
   * If we find something return 0, otherwise > 0, < 0 on error.
   */
  int btrfs_find_root(struct btrfs_root *root, const struct btrfs_key *search_key,
  		    struct btrfs_path *path, struct btrfs_root_item *root_item,
  		    struct btrfs_key *root_key)
  {
  	struct btrfs_key found_key;
  	struct extent_buffer *l;
  	int ret;
  	int slot;
  
  	ret = btrfs_search_slot(NULL, root, search_key, path, 0, 0);
  	if (ret < 0)
  		return ret;
  
  	if (search_key->offset != -1ULL) {	/* the search key is exact */
  		if (ret > 0)
  			goto out;
  	} else {
  		BUG_ON(ret == 0);		/* Logical error */
  		if (path->slots[0] == 0)
  			goto out;
  		path->slots[0]--;
  		ret = 0;
  	}
  
  	l = path->nodes[0];
  	slot = path->slots[0];
  
  	btrfs_item_key_to_cpu(l, &found_key, slot);
  	if (found_key.objectid != search_key->objectid ||
  	    found_key.type != BTRFS_ROOT_ITEM_KEY) {
  		ret = 1;
  		goto out;
  	}
  
  	if (root_item)
  		btrfs_read_root_item(l, slot, root_item);
  	if (root_key)
  		memcpy(root_key, &found_key, sizeof(found_key));
  out:
  	btrfs_release_path(path);
  	return ret;
  }
  
  void btrfs_set_root_node(struct btrfs_root_item *item,
  			 struct extent_buffer *node)
  {
  	btrfs_set_root_bytenr(item, node->start);
  	btrfs_set_root_level(item, btrfs_header_level(node));
  	btrfs_set_root_generation(item, btrfs_header_generation(node));
  }
  
  /*
   * copy the data in 'item' into the btree
   */
  int btrfs_update_root(struct btrfs_trans_handle *trans, struct btrfs_root
  		      *root, struct btrfs_key *key, struct btrfs_root_item
  		      *item)
  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	struct btrfs_path *path;
  	struct extent_buffer *l;
  	int ret;
  	int slot;
  	unsigned long ptr;
  	u32 old_len;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	ret = btrfs_search_slot(trans, root, key, path, 0, 1);
  	if (ret < 0)
  		goto out;
  
  	if (ret > 0) {
  		btrfs_crit(fs_info,
  			"unable to find root key (%llu %u %llu) in tree %llu",
  			key->objectid, key->type, key->offset,
  			root->root_key.objectid);
  		ret = -EUCLEAN;
  		btrfs_abort_transaction(trans, ret);
  		goto out;
  	}
  
  	l = path->nodes[0];
  	slot = path->slots[0];
  	ptr = btrfs_item_ptr_offset(l, slot);
  	old_len = btrfs_item_size_nr(l, slot);
  
  	/*
  	 * If this is the first time we update the root item which originated
  	 * from an older kernel, we need to enlarge the item size to make room
  	 * for the added fields.
  	 */
  	if (old_len < sizeof(*item)) {
  		btrfs_release_path(path);
  		ret = btrfs_search_slot(trans, root, key, path,
  				-1, 1);
  		if (ret < 0) {
  			btrfs_abort_transaction(trans, ret);
  			goto out;
  		}
  
  		ret = btrfs_del_item(trans, root, path);
  		if (ret < 0) {
  			btrfs_abort_transaction(trans, ret);
  			goto out;
  		}
  		btrfs_release_path(path);
  		ret = btrfs_insert_empty_item(trans, root, path,
  				key, sizeof(*item));
  		if (ret < 0) {
  			btrfs_abort_transaction(trans, ret);
  			goto out;
  		}
  		l = path->nodes[0];
  		slot = path->slots[0];
  		ptr = btrfs_item_ptr_offset(l, slot);
  	}
  
  	/*
  	 * Update generation_v2 so at the next mount we know the new root
  	 * fields are valid.
  	 */
  	btrfs_set_root_generation_v2(item, btrfs_root_generation(item));
  
  	write_extent_buffer(l, item, ptr, sizeof(*item));
  	btrfs_mark_buffer_dirty(path->nodes[0]);
  out:
  	btrfs_free_path(path);
  	return ret;
  }
  
  int btrfs_insert_root(struct btrfs_trans_handle *trans, struct btrfs_root *root,
  		      const struct btrfs_key *key, struct btrfs_root_item *item)
  {
  	/*
  	 * Make sure generation v1 and v2 match. See update_root for details.
  	 */
  	btrfs_set_root_generation_v2(item, btrfs_root_generation(item));
  	return btrfs_insert_item(trans, root, key, item, sizeof(*item));
  }
  
  int btrfs_find_orphan_roots(struct btrfs_fs_info *fs_info)
  {
  	struct btrfs_root *tree_root = fs_info->tree_root;
  	struct extent_buffer *leaf;
  	struct btrfs_path *path;
  	struct btrfs_key key;
  	struct btrfs_key root_key;
  	struct btrfs_root *root;
  	int err = 0;
  	int ret;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	key.objectid = BTRFS_ORPHAN_OBJECTID;
  	key.type = BTRFS_ORPHAN_ITEM_KEY;
  	key.offset = 0;
  
  	root_key.type = BTRFS_ROOT_ITEM_KEY;
  	root_key.offset = (u64)-1;
  
  	while (1) {
  		ret = btrfs_search_slot(NULL, tree_root, &key, path, 0, 0);
  		if (ret < 0) {
  			err = ret;
  			break;
  		}
  
  		leaf = path->nodes[0];
  		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
  			ret = btrfs_next_leaf(tree_root, path);
  			if (ret < 0)
  				err = ret;
  			if (ret != 0)
  				break;
  			leaf = path->nodes[0];
  		}
  
  		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
  		btrfs_release_path(path);
  
  		if (key.objectid != BTRFS_ORPHAN_OBJECTID ||
  		    key.type != BTRFS_ORPHAN_ITEM_KEY)
  			break;
  
  		root_key.objectid = key.offset;
  		key.offset++;
  
  		root = btrfs_get_fs_root(fs_info, &root_key, false);
  		err = PTR_ERR_OR_ZERO(root);
  		if (err && err != -ENOENT) {
  			break;
  		} else if (err == -ENOENT) {
  			struct btrfs_trans_handle *trans;
  
  			btrfs_release_path(path);
  
  			trans = btrfs_join_transaction(tree_root);
  			if (IS_ERR(trans)) {
  				err = PTR_ERR(trans);
  				btrfs_handle_fs_error(fs_info, err,
  					    "Failed to start trans to delete orphan item");
  				break;
  			}
  			err = btrfs_del_orphan_item(trans, tree_root,
  						    root_key.objectid);
  			btrfs_end_transaction(trans);
  			if (err) {
  				btrfs_handle_fs_error(fs_info, err,
  					    "Failed to delete root orphan item");
  				break;
  			}
  			continue;
  		}
  
  		WARN_ON(!test_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state));
  		if (btrfs_root_refs(&root->root_item) == 0) {
  			set_bit(BTRFS_ROOT_DEAD_TREE, &root->state);
  			btrfs_add_dead_root(root);
  		}
  		btrfs_put_root(root);
  	}
  
  	btrfs_free_path(path);
  	return err;
  }
  
  /* drop the root item for 'key' from the tree root */
  int btrfs_del_root(struct btrfs_trans_handle *trans,
  		   const struct btrfs_key *key)
  {
  	struct btrfs_root *root = trans->fs_info->tree_root;
  	struct btrfs_path *path;
  	int ret;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  	ret = btrfs_search_slot(trans, root, key, path, -1, 1);
  	if (ret < 0)
  		goto out;
  
  	BUG_ON(ret != 0);
  
  	ret = btrfs_del_item(trans, root, path);
  out:
  	btrfs_free_path(path);
  	return ret;
  }
  
  int btrfs_del_root_ref(struct btrfs_trans_handle *trans, u64 root_id,
  		       u64 ref_id, u64 dirid, u64 *sequence, const char *name,
  		       int name_len)
  
  {
  	struct btrfs_root *tree_root = trans->fs_info->tree_root;
  	struct btrfs_path *path;
  	struct btrfs_root_ref *ref;
  	struct extent_buffer *leaf;
  	struct btrfs_key key;
  	unsigned long ptr;
  	int err = 0;
  	int ret;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	key.objectid = root_id;
  	key.type = BTRFS_ROOT_BACKREF_KEY;
  	key.offset = ref_id;
  again:
  	ret = btrfs_search_slot(trans, tree_root, &key, path, -1, 1);
  	BUG_ON(ret < 0);
  	if (ret == 0) {
  		leaf = path->nodes[0];
  		ref = btrfs_item_ptr(leaf, path->slots[0],
  				     struct btrfs_root_ref);
  		ptr = (unsigned long)(ref + 1);
  		if ((btrfs_root_ref_dirid(leaf, ref) != dirid) ||
  		    (btrfs_root_ref_name_len(leaf, ref) != name_len) ||
  		    memcmp_extent_buffer(leaf, name, ptr, name_len)) {
  			err = -ENOENT;
  			goto out;
  		}
  		*sequence = btrfs_root_ref_sequence(leaf, ref);
  
  		ret = btrfs_del_item(trans, tree_root, path);
  		if (ret) {
  			err = ret;
  			goto out;
  		}
  	} else
  		err = -ENOENT;
  
  	if (key.type == BTRFS_ROOT_BACKREF_KEY) {
  		btrfs_release_path(path);
  		key.objectid = ref_id;
  		key.type = BTRFS_ROOT_REF_KEY;
  		key.offset = root_id;
  		goto again;
  	}
  
  out:
  	btrfs_free_path(path);
  	return err;
  }
  
  /*
   * add a btrfs_root_ref item.  type is either BTRFS_ROOT_REF_KEY
   * or BTRFS_ROOT_BACKREF_KEY.
   *
   * The dirid, sequence, name and name_len refer to the directory entry
   * that is referencing the root.
   *
   * For a forward ref, the root_id is the id of the tree referencing
   * the root and ref_id is the id of the subvol  or snapshot.
   *
   * For a back ref the root_id is the id of the subvol or snapshot and
   * ref_id is the id of the tree referencing it.
   *
   * Will return 0, -ENOMEM, or anything from the CoW path
   */
  int btrfs_add_root_ref(struct btrfs_trans_handle *trans, u64 root_id,
  		       u64 ref_id, u64 dirid, u64 sequence, const char *name,
  		       int name_len)
  {
  	struct btrfs_root *tree_root = trans->fs_info->tree_root;
  	struct btrfs_key key;
  	int ret;
  	struct btrfs_path *path;
  	struct btrfs_root_ref *ref;
  	struct extent_buffer *leaf;
  	unsigned long ptr;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	key.objectid = root_id;
  	key.type = BTRFS_ROOT_BACKREF_KEY;
  	key.offset = ref_id;
  again:
  	ret = btrfs_insert_empty_item(trans, tree_root, path, &key,
  				      sizeof(*ref) + name_len);
  	if (ret) {
  		btrfs_abort_transaction(trans, ret);
  		btrfs_free_path(path);
  		return ret;
  	}
  
  	leaf = path->nodes[0];
  	ref = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_root_ref);
  	btrfs_set_root_ref_dirid(leaf, ref, dirid);
  	btrfs_set_root_ref_sequence(leaf, ref, sequence);
  	btrfs_set_root_ref_name_len(leaf, ref, name_len);
  	ptr = (unsigned long)(ref + 1);
  	write_extent_buffer(leaf, name, ptr, name_len);
  	btrfs_mark_buffer_dirty(leaf);
  
  	if (key.type == BTRFS_ROOT_BACKREF_KEY) {
  		btrfs_release_path(path);
  		key.objectid = ref_id;
  		key.type = BTRFS_ROOT_REF_KEY;
  		key.offset = root_id;
  		goto again;
  	}
  
  	btrfs_free_path(path);
  	return 0;
  }
  
  /*
   * Old btrfs forgets to init root_item->flags and root_item->byte_limit
   * for subvolumes. To work around this problem, we steal a bit from
   * root_item->inode_item->flags, and use it to indicate if those fields
   * have been properly initialized.
   */
  void btrfs_check_and_init_root_item(struct btrfs_root_item *root_item)
  {
  	u64 inode_flags = btrfs_stack_inode_flags(&root_item->inode);
  
  	if (!(inode_flags & BTRFS_INODE_ROOT_ITEM_INIT)) {
  		inode_flags |= BTRFS_INODE_ROOT_ITEM_INIT;
  		btrfs_set_stack_inode_flags(&root_item->inode, inode_flags);
  		btrfs_set_root_flags(root_item, 0);
  		btrfs_set_root_limit(root_item, 0);
  	}
  }
  
  void btrfs_update_root_times(struct btrfs_trans_handle *trans,
  			     struct btrfs_root *root)
  {
  	struct btrfs_root_item *item = &root->root_item;
  	struct timespec64 ct;
  
  	ktime_get_real_ts64(&ct);
  	spin_lock(&root->root_item_lock);
  	btrfs_set_root_ctransid(item, trans->transid);
  	btrfs_set_stack_timespec_sec(&item->ctime, ct.tv_sec);
  	btrfs_set_stack_timespec_nsec(&item->ctime, ct.tv_nsec);
  	spin_unlock(&root->root_item_lock);
  }
  
  /*
   * btrfs_subvolume_reserve_metadata() - reserve space for subvolume operation
   * root: the root of the parent directory
   * rsv: block reservation
   * items: the number of items that we need do reservation
   * use_global_rsv: allow fallback to the global block reservation
   *
   * This function is used to reserve the space for snapshot/subvolume
   * creation and deletion. Those operations are different with the
   * common file/directory operations, they change two fs/file trees
   * and root tree, the number of items that the qgroup reserves is
   * different with the free space reservation. So we can not use
   * the space reservation mechanism in start_transaction().
   */
  int btrfs_subvolume_reserve_metadata(struct btrfs_root *root,
  				     struct btrfs_block_rsv *rsv, int items,
  				     bool use_global_rsv)
  {
  	u64 qgroup_num_bytes = 0;
  	u64 num_bytes;
  	int ret;
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
  
  	if (test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) {
  		/* One for parent inode, two for dir entries */
  		qgroup_num_bytes = 3 * fs_info->nodesize;
  		ret = btrfs_qgroup_reserve_meta_prealloc(root,
  				qgroup_num_bytes, true);
  		if (ret)
  			return ret;
  	}
  
  	num_bytes = btrfs_calc_insert_metadata_size(fs_info, items);
  	rsv->space_info = btrfs_find_space_info(fs_info,
  					    BTRFS_BLOCK_GROUP_METADATA);
  	ret = btrfs_block_rsv_add(root, rsv, num_bytes,
  				  BTRFS_RESERVE_FLUSH_ALL);
  
  	if (ret == -ENOSPC && use_global_rsv)
  		ret = btrfs_block_rsv_migrate(global_rsv, rsv, num_bytes, true);
  
  	if (ret && qgroup_num_bytes)
  		btrfs_qgroup_free_meta_prealloc(root, qgroup_num_bytes);
  
  	return ret;
  }
  
  void btrfs_subvolume_release_metadata(struct btrfs_fs_info *fs_info,
  				      struct btrfs_block_rsv *rsv)
  {
  	btrfs_block_rsv_release(fs_info, rsv, (u64)-1, NULL);
  }
  