[Nbd] [PATCH 3/8] mtd: use generic helper to set max_discard_sectors

[Namjae Jeon <linkinjeon@...17...>]

From: Namjae Jeon <namjae.jeon@...1329...>

It is better to use blk_queue_max_discard_sectors helper
function to set max_discard_sectors as it checks
max_discard_sectors upper limit UINT_MAX >> 9

similar issue was reported for mmc in below link
https://lkml.org/lkml/2013/4/1/292

If multiple discard requests get merged, merged discard request's
size exceeds 4GB, there is possibility that merged discard request's
__data_len field may overflow.

This patch fixes this issue.

Signed-off-by: Namjae Jeon <namjae.jeon@...1329...>
Signed-off-by: Vivek Trivedi <t.vivek@...1329...>
---
 drivers/mtd/mtd_blkdevs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
index 5ad39bb..cf35f99 100644
--- a/drivers/mtd/mtd_blkdevs.c
+++ b/drivers/mtd/mtd_blkdevs.c
@@ -417,7 +417,7 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
 
 	if (tr->discard) {
 		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, new->rq);
-		new->rq->limits.max_discard_sectors = UINT_MAX;
+		blk_queue_max_discard_sectors(new->rq, UINT_MAX >> 9);
 	}
 
 	gd->queue = new->rq;
-- 
1.7.9.5