From: Ming Lei <tom.leiming@gmail.com>
Date: Tue, 11 Nov 2014 16:15:41 +0000 (+0800)
Subject: block: blk-merge: fix blk_recount_segments()
X-Git-Tag: firefly_0821_release~176^2~2868^2
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=7f60dcaaf91e911002007c7ae885ff6ef0f36c0d;p=firefly-linux-kernel-4.4.55.git

block: blk-merge: fix blk_recount_segments()

For cloned bio, bio->bi_vcnt can't be used at all, and we
have resort to bio_segments() to figure out how many
segment there are in the bio.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
---

diff --git a/block/blk-merge.c b/block/blk-merge.c
index b3ac40aef46b..89b97b5e0881 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -97,19 +97,22 @@ void blk_recalc_rq_segments(struct request *rq)
 
 void blk_recount_segments(struct request_queue *q, struct bio *bio)
 {
-	bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
-			&q->queue_flags);
-	bool merge_not_need = bio->bi_vcnt < queue_max_segments(q);
+	unsigned short seg_cnt;
+
+	/* estimate segment number by bi_vcnt for non-cloned bio */
+	if (bio_flagged(bio, BIO_CLONED))
+		seg_cnt = bio_segments(bio);
+	else
+		seg_cnt = bio->bi_vcnt;
 
-	if (no_sg_merge && !bio_flagged(bio, BIO_CLONED) &&
-			merge_not_need)
-		bio->bi_phys_segments = bio->bi_vcnt;
+	if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
+			(seg_cnt < queue_max_segments(q)))
+		bio->bi_phys_segments = seg_cnt;
 	else {
 		struct bio *nxt = bio->bi_next;
 
 		bio->bi_next = NULL;
-		bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio,
-				no_sg_merge && merge_not_need);
+		bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
 		bio->bi_next = nxt;
 	}