Merge tag 'drm-intel-next-fixes-2017-04-27' of git://anongit.freedesktop.org/git...

[sfrench/cifs-2.6.git] / include / linux / blkdev.h

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 7548f332121ab733e908474e5e626bb9aecb59e3..01a696b0a4d3ae0118a2742c96d68775ef9f637a 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1672,12 +1672,36 @@ 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);
 
@@ -1690,12 +1714,12 @@ 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);