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-rw-r--r--include/linux/blkdev.h32
1 files changed, 28 insertions, 4 deletions
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 7548f332121a..01a696b0a4d3 100644
--- 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);