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Subject[PATCH] block: move sanity checking ahead of bi_front/back_seg_size updating
Date
If the bio_integrity_merge_rq() return false or nr_phys_segments exceeds
the max_segments, the merging fails, but the bi_front/back_seg_size may
have been modified. To avoid it, move the sanity checking ahead.

Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
---
block/blk-merge.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 99038830..14b6e37 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -553,6 +553,7 @@ static bool req_no_special_merge(struct request *req)
static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
struct request *next)
{
+ bool contig;
int total_phys_segments;
unsigned int seg_size =
req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
@@ -575,13 +576,9 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
return 0;

total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
- if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
- if (req->nr_phys_segments == 1)
- req->bio->bi_seg_front_size = seg_size;
- if (next->nr_phys_segments == 1)
- next->biotail->bi_seg_back_size = seg_size;
+ contig = blk_phys_contig_segment(q, req->biotail, next->bio);
+ if (contig)
total_phys_segments--;
- }

if (total_phys_segments > queue_max_segments(q))
return 0;
@@ -589,6 +586,13 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
if (blk_integrity_merge_rq(q, req, next) == false)
return 0;

+ if (contig) {
+ if (req->nr_phys_segments == 1)
+ req->bio->bi_seg_front_size = seg_size;
+ if (next->nr_phys_segments == 1)
+ next->biotail->bi_seg_back_size = seg_size;
+ }
+
/* Merge is OK... */
req->nr_phys_segments = total_phys_segments;
return 1;
--
2.7.4
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