btrfs: relocation: Remove is_cowonly_root()

This function is only used in read_fs_root(), which is just a wrapper of
btrfs_get_fs_root().

For all the mentioned essential roots except log root tree,
btrfs_get_fs_root() has its own quick path to grab them from fs_info
directly, thus no need for key.offset modification.

For subvolume trees, btrfs_get_fs_root() with key.offset == -1 is
completely fine.

For log trees and log root tree, it's impossible to hit them, as for
relocation all backrefs are fetched from commit root, which never
records log tree blocks.

Log tree blocks either get freed in regular transaction commit, or
replayed at mount time. At runtime we should never hit an backref for
log tree in extent tree.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 034f5f151a74988b39dec0d4c0aa38cdfeec45bc..6130ba69bc49e5f79d1c73f1b9cc0e194eefbcb9 100644 (file)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -640,21 +640,6 @@ static struct btrfs_root *find_reloc_root(struct reloc_control *rc,
        return btrfs_grab_root(root);
 }
 
-static int is_cowonly_root(u64 root_objectid)
-{
-       if (root_objectid == BTRFS_ROOT_TREE_OBJECTID ||
-           root_objectid == BTRFS_EXTENT_TREE_OBJECTID ||
-           root_objectid == BTRFS_CHUNK_TREE_OBJECTID ||
-           root_objectid == BTRFS_DEV_TREE_OBJECTID ||
-           root_objectid == BTRFS_TREE_LOG_OBJECTID ||
-           root_objectid == BTRFS_CSUM_TREE_OBJECTID ||
-           root_objectid == BTRFS_UUID_TREE_OBJECTID ||
-           root_objectid == BTRFS_QUOTA_TREE_OBJECTID ||
-           root_objectid == BTRFS_FREE_SPACE_TREE_OBJECTID)
-               return 1;
-       return 0;
-}
-
 static struct btrfs_root *read_fs_root(struct btrfs_fs_info *fs_info,
                                        u64 root_objectid)
 {
@@ -662,10 +647,7 @@ static struct btrfs_root *read_fs_root(struct btrfs_fs_info *fs_info,
 
        key.objectid = root_objectid;
        key.type = BTRFS_ROOT_ITEM_KEY;
-       if (is_cowonly_root(root_objectid))
-               key.offset = 0;
-       else
-               key.offset = (u64)-1;
+       key.offset = (u64)-1;
 
        return btrfs_get_fs_root(fs_info, &key, false);
 }