fs/btrfs/root-tree.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2
   3 #include "ctree.h"
   4
   5 int btrfs_find_last_root(struct btrfs_root *root, u64 objectid,
   6                         struct btrfs_root_item *item, struct btrfs_key *key)
   7 {
   8         struct btrfs_path *path;
   9         struct btrfs_key search_key;
  10         struct btrfs_key found_key;
  11         struct extent_buffer *l;
  12         int ret;
  13         int slot;
  14
  15         path = btrfs_alloc_path();
  16         if (!path)
  17                 return -ENOMEM;
  18
  19         search_key.objectid = objectid;
  20         search_key.type = BTRFS_ROOT_ITEM_KEY;
  21         search_key.offset = (u64)-1;
  22
  23         ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
  24         if (ret < 0)
  25                 goto out;
  26         if (path->slots[0] == 0) {
  27                 ret = -ENOENT;
  28                 goto out;
  29         }
  30
  31         BUG_ON(ret == 0);
  32         l = path->nodes[0];
  33         slot = path->slots[0] - 1;
  34         btrfs_item_key_to_cpu(l, &found_key, slot);
  35         if (found_key.type != BTRFS_ROOT_ITEM_KEY ||
  36             found_key.objectid != objectid) {
  37                 ret = -ENOENT;
  38                 goto out;
  39         }
  40         read_extent_buffer(l, item, btrfs_item_ptr_offset(l, slot),
  41                            sizeof(*item));
  42         memcpy(key, &found_key, sizeof(found_key));
  43         ret = 0;
  44 out:
  45         btrfs_free_path(path);
  46         return ret;
  47 }