blk_hw_contig_segment(): bad segment size checks

Two bugs in there:

- The virt oversize check should use the current bio hardware back
  size and the next bio front size, not the same bio. Spotted by
  Neil Brown.

- The segment size check should add hw front sizes, not total bio
  sizes. Spotted by James Bottomley

Acked-by: James Bottomley <James.Bottomley@SteelEye.com>
Acked-by: NeilBrown <neilb@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index c99b46354859..3e7801e49033 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -1304,9 +1304,9 @@ static int blk_hw_contig_segment(request_queue_t *q, struct bio *bio,
         if (unlikely(!bio_flagged(nxt, BIO_SEG_VALID)))
                 blk_recount_segments(q, nxt);
         if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
-            BIOVEC_VIRT_OVERSIZE(bio->bi_hw_front_size + bio->bi_hw_back_size))
+            BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size))
                 return 0;
-        if (bio->bi_size + nxt->bi_size > q->max_segment_size)
+        if (bio->bi_hw_back_size + nxt->bi_hw_front_size > q->max_segment_size)
                 return 0;
 
         return 1;