[PATCH 5/8] nbd: use generic helper to set max_discard_sectors

From: Namjae Jeon
Date: Sat Apr 13 2013 - 09:39:35 EST

From: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>

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

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@xxxxxxxxxxx>
Signed-off-by: Vivek Trivedi <t.vivek@xxxxxxxxxxx>
drivers/block/nbd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 7fecc78..0a081bc 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -854,7 +854,7 @@ static int __init nbd_init(void)
queue_flag_set_unlocked(QUEUE_FLAG_NONROT, disk->queue);
disk->queue->limits.discard_granularity = 512;
- disk->queue->limits.max_discard_sectors = UINT_MAX;
+ blk_queue_max_discard_sectors(disk->queue, UINT_MAX >> 9);
disk->queue->limits.discard_zeroes_data = 0;


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