btrfs: use simple_dir_inode_operations for placeholder subvolume directory

When you snapshot a subvolume containing a subvolume, you get a
placeholder directory where the subvolume would be. These directories
have their own btrfs_dir_ro_inode_operations.

Al pointed out [1] that these directories can use simple_lookup()
instead of btrfs_lookup(), as they are always empty. Furthermore, they
can use the default generic_permission() instead of btrfs_permission();
the additional checks in the latter don't matter because we can't write
to the directory anyways. Finally, they can use the default
generic_update_time() instead of btrfs_update_time(), as the inode
doesn't exist on disk and doesn't need any special handling.

All together, this means that we can get rid of
btrfs_dir_ro_inode_operations and use simple_dir_inode_operations
instead.

1: https://lore.kernel.org/linux-btrfs/[email protected]/

Cc: Al Viro <[email protected]>
Reviewed-by: Josef Bacik <[email protected]>
Signed-off-by: Omar Sandoval <[email protected]>
Reviewed-by: David Sterba <[email protected]>
[ add comment ]
Signed-off-by: David Sterba <[email protected]>

0 files changed, 0 insertions, 0 deletions