[Nbd] [PATCH 6/8] brd: 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/block/brd.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index f1a29f8..108646d 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -479,7 +479,7 @@ static struct brd_device *brd_alloc(int i)
 	blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);
 
 	brd->brd_queue->limits.discard_granularity = PAGE_SIZE;
-	brd->brd_queue->limits.max_discard_sectors = UINT_MAX;
+	blk_queue_max_discard_sectors(brd->brd_queue, UINT_MAX >> 9);
 	brd->brd_queue->limits.discard_zeroes_data = 1;
 	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, brd->brd_queue);
 
-- 
1.7.9.5