[dm-devel] [PATCH] dm-table: set non-zero q->limits.discard_granularity

[Mikulas Patocka]

Hi Mike

Could you send this to Linus before v5.9 is released?

Mikulas



From: Mikulas Patocka <mpatocka at redhat.com>

If q->limits.discard_granularity is zero, the block core will warn in
__blkdev_issue_discard. This patch sets it to a minimum - 512 bytes.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
Fixes: b35fd7422c2f ("block: check queue's limits.discard_granularity in __blkdev_issue_discard()")
Fixes: 9b15d109a6b2 ("block: improve discard bio alignment in __blkdev_issue_discard()")
Fixes: c52abf563049 ("loop: Better discard support for block devices")

---
 drivers/md/dm-table.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Index: linux-2.6/drivers/md/dm-table.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-table.c	2020-08-31 12:08:27.000000000 +0200
+++ linux-2.6/drivers/md/dm-table.c	2020-09-24 16:23:55.000000000 +0200
@@ -1858,8 +1858,11 @@ void dm_table_set_restrictions(struct dm
 		q->limits.discard_granularity = 0;
 		q->limits.discard_alignment = 0;
 		q->limits.discard_misaligned = 0;
-	} else
+	} else {
 		blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
+		if (q->limits.discard_granularity < 512)
+			q->limits.discard_granularity = 512;
+	}
 
 	if (dm_table_supports_secure_erase(t))
 		blk_queue_flag_set(QUEUE_FLAG_SECERASE, q);