raid5: set bio bi_vcnt 0 for discard request

SCSI layer will add new payload for discard request. If two bios are merged
to one, the second bio has bi_vcnt 1 which is set in raid5. This will confuse
SCSI and cause oops.

Suitable for backport to 3.7+

Cc: stable@vger.kernel.org (v3.7+)
Reported-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 7ff4f252ca1a..302d7cd2076c 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -778,6 +778,12 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
                         bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
                         bi->bi_io_vec[0].bv_offset = 0;
                         bi->bi_size = STRIPE_SIZE;
+                        /*
+                         * If this is discard request, set bi_vcnt 0. We don't
+                         * want to confuse SCSI because SCSI will replace payload
+                         */
+                        if (rw & REQ_DISCARD)
+                                bi->bi_vcnt = 0;
                         if (rrdev)
                                 set_bit(R5_DOUBLE_LOCKED, &sh->dev[i].flags);
 
@@ -816,6 +822,12 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
                         rbi->bi_io_vec[0].bv_len = STRIPE_SIZE;
                         rbi->bi_io_vec[0].bv_offset = 0;
                         rbi->bi_size = STRIPE_SIZE;
+                        /*
+                         * If this is discard request, set bi_vcnt 0. We don't
+                         * want to confuse SCSI because SCSI will replace payload
+                         */
+                        if (rw & REQ_DISCARD)
+                                rbi->bi_vcnt = 0;
                         if (conf->mddev->gendisk)
                                 trace_block_bio_remap(bdev_get_queue(rbi->bi_bdev),
                                                       rbi, disk_devt(conf->mddev->gendisk),