[PATCH 2/4] xfs_scrub: detect infinite loops when scanning inodes

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

During an inode scan (aka phase 3) when we're scanning the inode btree
to find files to check, make sure that each invocation of inumbers
actually gives us an inobt record with a startino that's at least as
large as what we asked for so that we always make forward progress.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 scrub/inodes.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)


diff --git a/scrub/inodes.c b/scrub/inodes.c
index 63865113..cc73da7f 100644
--- a/scrub/inodes.c
+++ b/scrub/inodes.c
@@ -119,6 +119,7 @@ scan_ag_inodes(
 	struct scrub_ctx	*ctx = (struct scrub_ctx *)wq->wq_ctx;
 	struct xfs_bulkstat	*bs;
 	struct xfs_inumbers	*inumbers;
+	uint64_t		nextino = cvt_agino_to_ino(&ctx->mnt, agno, 0);
 	int			i;
 	int			error;
 	int			stale_count = 0;
@@ -153,6 +154,21 @@ scan_ag_inodes(
 	/* Find the inode chunk & alloc mask */
 	error = -xfrog_inumbers(&ctx->mnt, ireq);
 	while (!error && !si->aborted && ireq->hdr.ocount > 0) {
+		/*
+		 * Make sure that we always make forward progress while we
+		 * scan the inode btree.
+		 */
+		if (nextino > inumbers->xi_startino) {
+			str_corrupt(ctx, descr,
+	_("AG %u inode btree is corrupt near agino %lu, got %lu"), agno,
+				cvt_ino_to_agino(&ctx->mnt, nextino),
+				cvt_ino_to_agino(&ctx->mnt,
+						ireq->inumbers[0].xi_startino));
+			si->aborted = true;
+			break;
+		}
+		nextino = ireq->hdr.ino;
+
 		/*
 		 * We can have totally empty inode chunks on filesystems where
 		 * there are more than 64 inodes per block.  Skip these.