Btrfs: Support reading/writing on disk free ino cache

This is similar to block group caching.

We dedicate a special inode in fs tree to save free ino cache.

At the very first time we create/delete a file after mount, the free ino
cache will be loaded from disk into memory. When the fs tree is commited,
the cache will be written back to disk.

To keep compatibility, we check the root generation against the generation
of the special inode when loading the cache, so the loading will fail
if the btrfs filesystem was mounted in an older kernel before.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index af06e6b6ceaa..8f2613f779ed 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -65,6 +65,17 @@ int btrfs_write_out_cache(struct btrfs_root *root,
 			  struct btrfs_block_group_cache *block_group,
 			  struct btrfs_path *path);
 
+struct inode *lookup_free_ino_inode(struct btrfs_root *root,
+				    struct btrfs_path *path);
+int create_free_ino_inode(struct btrfs_root *root,
+			  struct btrfs_trans_handle *trans,
+			  struct btrfs_path *path);
+int load_free_ino_cache(struct btrfs_fs_info *fs_info,
+			struct btrfs_root *root);
+int btrfs_write_out_ino_cache(struct btrfs_root *root,
+			      struct btrfs_trans_handle *trans,
+			      struct btrfs_path *path);
+
 void btrfs_init_free_space_ctl(struct btrfs_block_group_cache *block_group);
 int __btrfs_add_free_space(struct btrfs_free_space_ctl *ctl,
 			   u64 bytenr, u64 size);