From 02e707424c2eadbcda68cd38876c9f4434ca8e1a Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Tue, 24 Nov 2015 10:35:30 +0800 Subject: [PATCH] blk-merge: fix blk_bio_segment_split Commit bdced438acd83a(block: setup bi_phys_segments after splitting) introduces function of computing bio->bi_phys_segments during bio splitting. Unfortunately both bio->bi_seg_front_size and bio->bi_seg_back_size arn't computed, so too many physical segments may be obtained for one request since both the two are used to check if one segment across two bios can be possible. This patch fixes the issue by computing the two variables in blk_bio_segment_split(). Fixes: bdced438acd83a(block: setup bi_phys_segments after splitting) Reported-by: Michael Ellerman Reported-by: Mark Salter Tested-by: Laurent Dufour Tested-by: Mark Salter Signed-off-by: Ming Lei Signed-off-by: Jens Axboe --- block/blk-merge.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index f2efe8ae75bb..50793cdc5331 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -76,6 +76,9 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, struct bio_vec bv, bvprv, *bvprvp = NULL; struct bvec_iter iter; unsigned seg_size = 0, nsegs = 0, sectors = 0; + unsigned front_seg_size = bio->bi_seg_front_size; + bool do_split = true; + struct bio *new = NULL; bio_for_each_segment(bv, bio, iter) { if (sectors + (bv.bv_len >> 9) > queue_max_sectors(q)) @@ -111,13 +114,26 @@ new_segment: bvprvp = &bvprv; seg_size = bv.bv_len; sectors += bv.bv_len >> 9; + + if (nsegs == 1 && seg_size > front_seg_size) + front_seg_size = seg_size; } - *segs = nsegs; - return NULL; + do_split = false; split: *segs = nsegs; - return bio_split(bio, sectors, GFP_NOIO, bs); + + if (do_split) { + new = bio_split(bio, sectors, GFP_NOIO, bs); + if (new) + bio = new; + } + + bio->bi_seg_front_size = front_seg_size; + if (seg_size > bio->bi_seg_back_size) + bio->bi_seg_back_size = seg_size; + + return do_split ? new : NULL; } void blk_queue_split(struct request_queue *q, struct bio **bio,