btrfs: update outdated comment at btrfs_orphan_cleanup()

btrfs_orphan_cleanup() has a comment referring to find_dead_roots, but
function does not exists since commit cb517eabba4f10 ("Btrfs: cleanup the
similar code of the fs root read"). What we use now to find and load dead
roots is btrfs_find_orphan_roots(). So update the comment and make it a
bit more detailed about why we can not delete an orphan item for a root.

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

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 8f21036..1e0e20a 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3386,15 +3386,19 @@ int btrfs_orphan_cleanup(struct btrfs_root *root)
                        int is_dead_root = 0;
 
                        /*
-                        * this is an orphan in the tree root. Currently these
+                        * This is an orphan in the tree root. Currently these
                         * could come from 2 sources:
-                        *  a) a snapshot deletion in progress
+                        *  a) a root (snapshot/subvolume) deletion in progress
                         *  b) a free space cache inode
-                        * We need to distinguish those two, as the snapshot
-                        * orphan must not get deleted.
-                        * find_dead_roots already ran before us, so if this
-                        * is a snapshot deletion, we should find the root
-                        * in the fs_roots radix tree.
+                        * We need to distinguish those two, as the orphan item
+                        * for a root must not get deleted before the deletion
+                        * of the snapshot/subvolume's tree completes.
+                        *
+                        * btrfs_find_orphan_roots() ran before us, which has
+                        * found all deleted roots and loaded them into
+                        * fs_info->fs_roots_radix. So here we can find if an
+                        * orphan item corresponds to a deleted root by looking
+                        * up the root from that radix tree.
                         */
 
                        spin_lock(&fs_info->fs_roots_radix_lock);