X-Git-Url: https://git.karo-electronics.de/?a=blobdiff_plain;f=include%2Flinux%2Fblkdev.h;h=83d28623645f33f0b54596116905012bcc800826;hb=694752922b12bd318aa80191bd9d8c3dcfb39055;hp=d098c66b3ab01b73e6b48380b5dc06f81388914f;hpb=9438b3e080beccf6022138ea62192d55cc7dc4ed;p=karo-tx-linux.git

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d098c66b3ab0..83d28623645f 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1655,12 +1655,36 @@ static inline bool bios_segs_mergeable(struct request_queue *q,
 	return true;
 }
 
-static inline bool bio_will_gap(struct request_queue *q, struct bio *prev,
-			 struct bio *next)
+static inline bool bio_will_gap(struct request_queue *q,
+				struct request *prev_rq,
+				struct bio *prev,
+				struct bio *next)
 {
 	if (bio_has_data(prev) && queue_virt_boundary(q)) {
 		struct bio_vec pb, nb;
 
+		/*
+		 * don't merge if the 1st bio starts with non-zero
+		 * offset, otherwise it is quite difficult to respect
+		 * sg gap limit. We work hard to merge a huge number of small
+		 * single bios in case of mkfs.
+		 */
+		if (prev_rq)
+			bio_get_first_bvec(prev_rq->bio, &pb);
+		else
+			bio_get_first_bvec(prev, &pb);
+		if (pb.bv_offset)
+			return true;
+
+		/*
+		 * We don't need to worry about the situation that the
+		 * merged segment ends in unaligned virt boundary:
+		 *
+		 * - if 'pb' ends aligned, the merged segment ends aligned
+		 * - if 'pb' ends unaligned, the next bio must include
+		 *   one single bvec of 'nb', otherwise the 'nb' can't
+		 *   merge with 'pb'
+		 */
 		bio_get_last_bvec(prev, &pb);
 		bio_get_first_bvec(next, &nb);
 
@@ -1673,12 +1697,12 @@ static inline bool bio_will_gap(struct request_queue *q, struct bio *prev,
 
 static inline bool req_gap_back_merge(struct request *req, struct bio *bio)
 {
-	return bio_will_gap(req->q, req->biotail, bio);
+	return bio_will_gap(req->q, req, req->biotail, bio);
 }
 
 static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
 {
-	return bio_will_gap(req->q, bio, req->bio);
+	return bio_will_gap(req->q, NULL, bio, req->bio);
 }
 
 int kblockd_schedule_work(struct work_struct *work);