From 0b76defb03d5afb12fe6b778daab0eeca695f48e Mon Sep 17 00:00:00 2001
From: David Disseldorp <ddiss@suse.de>
Date: Thu, 2 Nov 2017 01:05:11 +0100
Subject: [PATCH 2/3] rbd: set discard_alignment to zero
Git-commit: 7c084289795bc0f3b9ab315ac3c8d269dd4d0215
Patch-mainline: v4.15-rc1
References: bsc#1064320

RBD devices are currently incorrectly initialised with the block queue
discard_alignment set to the underlying RADOS object size.

As per Documentation/ABI/testing/sysfs-block:
  The discard_alignment parameter indicates how many bytes the beginning
  of the device is offset from the internal allocation unit's natural
  alignment.

Correcting the discard_alignment parameter from the RADOS object size to
zero (the blk_set_default_limits() default) has no effect on how discard
requests are propagated through the block layer - @alignment in
__blkdev_issue_discard() remains zero. However, it does fix the UNMAP
granularity alignment value advertised to SCSI initiators via the Block
Limits VPD.

Signed-off-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Luis Henriques <lhenriques@suse.com>

---
 drivers/block/rbd.c |    1 -
 1 file changed, 1 deletion(-)

--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -4419,7 +4419,6 @@ static int rbd_init_disk(struct rbd_devi
 	/* enable the discard support */
 	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
 	q->limits.discard_granularity = segment_size;
-	q->limits.discard_alignment = segment_size;
 	blk_queue_max_discard_sectors(q, segment_size / SECTOR_SIZE);
 	blk_queue_max_write_zeroes_sectors(q, segment_size / SECTOR_SIZE);