btrfs: add comment to struct btrfs_fs_info::dirty_cowonly_roots

Add a comment to struct btrfs_fs_info::dirty_cowonly_roots to mention
that struct btrfs_fs_info::trans_lock is the lock that protects that
list.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
index 396e2a4..203d2a2 100644 (file)
--- a/fs/btrfs/fs.h
+++ b/fs/btrfs/fs.h
@@ -576,6 +576,7 @@ struct btrfs_fs_info {
        s32 dirty_metadata_batch;
        s32 delalloc_batch;
 
+       /* Protected by 'trans_lock'. */
        struct list_head dirty_cowonly_roots;
 
        struct btrfs_fs_devices *fs_devices;