From: Damien Le Moal <damien.lemoal@wdc.com>
Date: Tue, 5 Sep 2017 20:55:35 +0900
Subject: [PATCH] scsi: sd: Align maximum write same blocks to physical block
 size
References: bsc#1077989
Git-commit: b7af62a945706e32b987f1dd0cc86bb41a8210c3
Patch-mainline: v4.15-rc1

Reporting a maximum number of blocks that is not aligned on the device
physical size would cause a large write same request to be split into
physically unaligned chunks by __blkdev_issue_write_zeroes() and
__blkdev_issue_write_same(), even if the caller of these functions took
care to align its request to physical sectors.

Make sure the maximum reported is aligned to the device physical block
size. This is only an optional optimization for regular disks, but this
is mandatory to avoid failure of large write same requests directed at
sequential write required zones of host-managed ZBC disks.

[mkp: tweaked commit message]

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/sd.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 9a131a8d0d7b..b838cd69d7f3 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -898,6 +898,26 @@ static void sd_config_write_same(struct scsi_disk *sdkp)
 	else
 		sdkp->zeroing_mode = SD_ZERO_WRITE;
 
+	if (sdkp->max_ws_blocks &&
+	    sdkp->physical_block_size > logical_block_size) {
+		/*
+		 * Reporting a maximum number of blocks that is not aligned
+		 * on the device physical size would cause a large write same
+		 * request to be split into physically unaligned chunks by
+		 * __blkdev_issue_write_zeroes() and __blkdev_issue_write_same()
+		 * even if the caller of these functions took care to align the
+		 * large request. So make sure the maximum reported is aligned
+		 * to the device physical block size. This is only an optional
+		 * optimization for regular disks, but this is mandatory to
+		 * avoid failure of large write same requests directed at
+		 * sequential write required zones of host-managed ZBC disks.
+		 */
+		sdkp->max_ws_blocks =
+			round_down(sdkp->max_ws_blocks,
+				   bytes_to_logical(sdkp->device,
+						    sdkp->physical_block_size));
+	}
+
 out:
 	blk_queue_max_write_same_sectors(q, sdkp->max_ws_blocks *
 					 (logical_block_size >> 9));
-- 
2.12.3