[PATCH] mm: Fix a regression where MS_SNAP_STABLE (stable pages snapshotting) was ignored

["Darrick J. Wong" <darrick.wong@oracle.com>]

The "force" parameter in __blk_queue_bounce was being ignored, which means that
stable page snapshots are not always happening (on ext3).  This of course
leads to DIF disks reporting checksum errors, so fix this regression.

The regression was introduced in commit 6bc454d1 (bounce: Refactor
__blk_queue_bounce to not use bi_io_vec)

Reported-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 mm/bounce.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/bounce.c b/mm/bounce.c
index c9f0a43..5a7d58f 100644
--- a/mm/bounce.c
+++ b/mm/bounce.c
@@ -204,6 +204,8 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 	struct bio_vec *to, *from;
 	unsigned i;
 
+	if (force)
+		goto bounce;
 	bio_for_each_segment(from, *bio_orig, i)
 		if (page_to_pfn(from->bv_page) > queue_bounce_pfn(q))
 			goto bounce;