[PATCH 32/32] xfs_scrub: don't merge over unused space when data checksums are enabled

[Christoph Hellwig <hch@lst.de>]

Unused space could be lost space at mount time for which no metadata was
recorded, and we thus might not have valid checksums for it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 scrub/read_verify.c | 33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/scrub/read_verify.c b/scrub/read_verify.c
index 311ea1c29008..0c3bec104d16 100644
--- a/scrub/read_verify.c
+++ b/scrub/read_verify.c
@@ -542,20 +542,33 @@ try_read_verify_schedule_io(
 
 	/*
 	 * If we have a stashed IO, we haven't changed pools, the error
-	 * reporting is the same, and the two extents are close,
-	 * we can combine them.
+	 * reporting is the same, and the two extents are close, we can combine
+	 * them.
+	 *
+	 * If the file system has data checksums enabled, only merge fully
+	 * contigous ranges, as unused data might have invalid checksums.
 	 */
-	if (rs->rvp == rvp && rs->io_length > 0 &&
-	    ((start >= rs->io_start && start <= rv_end + locality) ||
-	     (rs->io_start >= start &&
-	      rs->io_start <= req_end + locality))) {
-		rs->io_start = min(rs->io_start, start);
-		rs->io_length = max(req_end, rv_end) - rs->io_start;
-
-		return true;
+	if (rs->rvp != rvp || !rs->io_length)
+		return false;
+
+	if (rvp->ctx->mnt.fsgeom.flags & XFS_FSOP_GEOM_FLAGS_DATA_CSUM) {
+		if (start == rv_end)
+			goto merge;
+		if (rs->io_start == req_end)
+			goto merge;
+	} else {
+		if (start >= rs->io_start && start <= rv_end + locality)
+			goto merge;
+		if (rs->io_start >= start && rs->io_start <= req_end + locality)
+			goto merge;
 	}
 
 	return false;
+
+merge:
+	rs->io_start = min(rs->io_start, start);
+	rs->io_length = max(req_end, rv_end) - rs->io_start;
+	return true;
 }
 
 /* Did read verification succeed? */
-- 
2.53.0