xfs: don't allocate scrub contexts on the stack

Convert the on-stack scrub context, btree scrub context, and da btree
scrub context into a heap allocation so that we reduce stack usage and
gain the ability to handle tall btrees without issue.

Specifically, this saves us ~208 bytes for the dabtree scrub, ~464 bytes
for the btree scrub, and ~200 bytes for the main scrub context.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 35 insertions, 29 deletions

diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c
index 51e4c61916d2..8d528d35b725 100644
--- a/fs/xfs/scrub/scrub.c
+++ b/fs/xfs/scrub/scrub.c
@@ -461,15 +461,10 @@ xfs_scrub_metadata(
 	struct file			*file,
 	struct xfs_scrub_metadata	*sm)
 {
-	struct xfs_scrub		sc = {
-		.file			= file,
-		.sm			= sm,
-	};
+	struct xfs_scrub		*sc;
 	struct xfs_mount		*mp = XFS_I(file_inode(file))->i_mount;
 	int				error = 0;
 
-	sc.mp = mp;
-
 	BUILD_BUG_ON(sizeof(meta_scrub_ops) !=
 		(sizeof(struct xchk_meta_ops) * XFS_SCRUB_TYPE_NR));
 
@@ -489,59 +484,68 @@ xfs_scrub_metadata(
 
 	xchk_experimental_warning(mp);
 
-	sc.ops = &meta_scrub_ops[sm->sm_type];
-	sc.sick_mask = xchk_health_mask_for_scrub_type(sm->sm_type);
+	sc = kmem_zalloc(sizeof(struct xfs_scrub), KM_NOFS | KM_MAYFAIL);
+	if (!sc) {
+		error = -ENOMEM;
+		goto out;
+	}
+
+	sc->mp = mp;
+	sc->file = file;
+	sc->sm = sm;
+	sc->ops = &meta_scrub_ops[sm->sm_type];
+	sc->sick_mask = xchk_health_mask_for_scrub_type(sm->sm_type);
 retry_op:
 	/*
 	 * When repairs are allowed, prevent freezing or readonly remount while
 	 * scrub is running with a real transaction.
 	 */
 	if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) {
-		error = mnt_want_write_file(sc.file);
+		error = mnt_want_write_file(sc->file);
 		if (error)
-			goto out;
+			goto out_sc;
 	}
 
 	/* Set up for the operation. */
-	error = sc.ops->setup(&sc);
+	error = sc->ops->setup(sc);
 	if (error)
 		goto out_teardown;
 
 	/* Scrub for errors. */
-	error = sc.ops->scrub(&sc);
-	if (!(sc.flags & XCHK_TRY_HARDER) && error == -EDEADLOCK) {
+	error = sc->ops->scrub(sc);
+	if (!(sc->flags & XCHK_TRY_HARDER) && error == -EDEADLOCK) {
 		/*
 		 * Scrubbers return -EDEADLOCK to mean 'try harder'.
 		 * Tear down everything we hold, then set up again with
 		 * preparation for worst-case scenarios.
 		 */
-		error = xchk_teardown(&sc, 0);
+		error = xchk_teardown(sc, 0);
 		if (error)
-			goto out;
-		sc.flags |= XCHK_TRY_HARDER;
+			goto out_sc;
+		sc->flags |= XCHK_TRY_HARDER;
 		goto retry_op;
 	} else if (error || (sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE))
 		goto out_teardown;
 
-	xchk_update_health(&sc);
+	xchk_update_health(sc);
 
-	if ((sc.sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) &&
-	    !(sc.flags & XREP_ALREADY_FIXED)) {
+	if ((sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) &&
+	    !(sc->flags & XREP_ALREADY_FIXED)) {
 		bool needs_fix;
 
 		/* Let debug users force us into the repair routines. */
 		if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_FORCE_SCRUB_REPAIR))
-			sc.sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
+			sc->sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
 
-		needs_fix = (sc.sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
-						XFS_SCRUB_OFLAG_XCORRUPT |
-						XFS_SCRUB_OFLAG_PREEN));
+		needs_fix = (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
+						 XFS_SCRUB_OFLAG_XCORRUPT |
+						 XFS_SCRUB_OFLAG_PREEN));
 		/*
 		 * If userspace asked for a repair but it wasn't necessary,
 		 * report that back to userspace.
 		 */
 		if (!needs_fix) {
-			sc.sm->sm_flags |= XFS_SCRUB_OFLAG_NO_REPAIR_NEEDED;
+			sc->sm->sm_flags |= XFS_SCRUB_OFLAG_NO_REPAIR_NEEDED;
 			goto out_nofix;
 		}
 
@@ -549,26 +553,28 @@ retry_op:
 		 * If it's broken, userspace wants us to fix it, and we haven't
 		 * already tried to fix it, then attempt a repair.
 		 */
-		error = xrep_attempt(&sc);
+		error = xrep_attempt(sc);
 		if (error == -EAGAIN) {
 			/*
 			 * Either the repair function succeeded or it couldn't
 			 * get all the resources it needs; either way, we go
 			 * back to the beginning and call the scrub function.
 			 */
-			error = xchk_teardown(&sc, 0);
+			error = xchk_teardown(sc, 0);
 			if (error) {
 				xrep_failure(mp);
-				goto out;
+				goto out_sc;
 			}
 			goto retry_op;
 		}
 	}
 
 out_nofix:
-	xchk_postmortem(&sc);
+	xchk_postmortem(sc);
 out_teardown:
-	error = xchk_teardown(&sc, error);
+	error = xchk_teardown(sc, error);
+out_sc:
+	kmem_free(sc);
 out:
 	trace_xchk_done(XFS_I(file_inode(file)), sm, error);
 	if (error == -EFSCORRUPTED || error == -EFSBADCRC) {