[PATCH 7/8] dm thin: use generic helper to set max_discard_sectors

[Namjae Jeon]

From: Namjae Jeon <namjae.jeon at samsung.com>

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 at samsung.com>
Signed-off-by: Vivek Trivedi <t.vivek at samsung.com>
---
 drivers/md/dm-thin.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 905b75f..237295a 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2513,7 +2513,8 @@ static void set_discard_limits(struct pool_c *pt, struct queue_limits *limits)
 	struct pool *pool = pt->pool;
 	struct queue_limits *data_limits;
 
-	limits->max_discard_sectors = pool->sectors_per_block;
+	blk_queue_max_discard_sectors(bdev_get_queue(pt->data_dev->bdev),
+					pool->sectors_per_block);
 
 	/*
 	 * discard_granularity is just a hint, and not enforced.
-- 
1.7.9.5