[PATCH] btrfs: update outdated comment at btrfs_orphan_cleanup()

[PATCH] btrfs: update outdated comment at btrfs_orphan_cleanup()

[fdmanana]

From: Filipe Manana <fdmanana@suse.com>

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>
---
 fs/btrfs/inode.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index ddbac78c4abe..31717ef76a90 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3383,15 +3383,19 @@ 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);
-- 
2.28.0

Re: [PATCH] btrfs: update outdated comment at btrfs_orphan_cleanup()

[David Sterba]

On Tue, Mar 16, 2021 at 04:54:13PM +0000, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> 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>

Added to misc-next, thanks.