xfs_scrub: account only data extent tail after an overlap

Codex points out that the fsmap overlap handling in phase7 isn't quite
right -- if we already saw part of the current fsmapping, we should
*subtract* the overlap, not set the length to it!  Fix that.

Cc: linux-xfs@vger.kernel.org # v4.15.0
Fixes: 698c6c7cb8ba75 ("xfs_scrub: check summary counters")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/scrub/phase7.c b/scrub/phase7.c
index 3b765931a304a9ac3c6942844162abfc6997e82a..4a25c521fa0c76aa1c1abb2000a25268b2bfebd2 100644 (file)
--- a/scrub/phase7.c
+++ b/scrub/phase7.c
@@ -127,7 +127,7 @@ count_block_summary(
                if (counts->next_phys >= fsmap->fmr_physical + len)
                        return 0;
                else if (counts->next_phys > fsmap->fmr_physical)
-                       len = counts->next_phys - fsmap->fmr_physical;
+                       len -= counts->next_phys - fsmap->fmr_physical;
                counts->dbytes += len;
                counts->next_phys = fsmap->fmr_physical + fsmap->fmr_length;
                break;