[PATCH 2/6] xfs: don't double-lock when deleting a self-referential directory

From: Darrick J. Wong <[email protected]>

LOLLM notices that the dirtree scrubber can detect a directory that
refers to itself.  In this case, it's not correct for the directory tree
repair code to try to iolock/ilock both sc->ip and dp, because they're
the same inode.  Fix this by detecting that corner case and handling it
appropriately.

Cc: <[email protected]> # v6.10
Fixes: 3f31406aef493b ("xfs: fix corruptions in the directory tree")
Signed-off-by: "Darrick J. Wong" <[email protected]>
Assisted-by: LOLLM # finding obvious bugs
Reviewed-by: Christoph Hellwig <[email protected]>
---
 fs/xfs/scrub/dirtree_repair.c |   22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)


diff --git a/fs/xfs/scrub/dirtree_repair.c b/fs/xfs/scrub/dirtree_repair.c
index 1c0d7ea4a5be6a..bbf6acf6fd400c 100644
--- a/fs/xfs/scrub/dirtree_repair.c
+++ b/fs/xfs/scrub/dirtree_repair.c
@@ -349,6 +349,8 @@ xrep_dirtree_unlink_iolock(
 
 	ASSERT(sc->ilock_flags & XFS_IOLOCK_EXCL);
 
+	if (sc->ip == dp)
+		return 0;
 	if (xfs_ilock_nowait(dp, XFS_IOLOCK_EXCL))
 		return 0;
 
@@ -400,8 +402,18 @@ xrep_dirtree_unlink(
 	 * directory code can handle a reservationless update.
 	 */
 	resblks = xfs_remove_space_res(mp, step->name_len);
-	error = xfs_trans_alloc_dir(dp, &M_RES(mp)->tr_remove, sc->ip,
-			&resblks, &sc->tp, &dontcare);
+	if (sc->ip == dp) {
+again:
+		error = xfs_trans_alloc_inode(dp, &M_RES(mp)->tr_remove,
+				resblks, 0, false, &sc->tp);
+		if ((error == -ENOSPC || error == -EDQUOT) && resblks > 0) {
+			resblks = 0;
+			goto again;
+		}
+	} else {
+		error = xfs_trans_alloc_dir(dp, &M_RES(mp)->tr_remove, sc->ip,
+				&resblks, &sc->tp, &dontcare);
+	}
 	if (error)
 		goto out_iolock;
 
@@ -489,9 +501,11 @@ xrep_dirtree_unlink(
 	xchk_trans_cancel(sc);
 out_ilock:
 	xfs_iunlock(sc->ip, XFS_ILOCK_EXCL);
-	xfs_iunlock(dp, XFS_ILOCK_EXCL);
+	if (dp != sc->ip)
+		xfs_iunlock(dp, XFS_ILOCK_EXCL);
 out_iolock:
-	xfs_iunlock(dp, XFS_IOLOCK_EXCL);
+	if (dp != sc->ip)
+		xfs_iunlock(dp, XFS_IOLOCK_EXCL);
 	return error;
 }