[PATCH] scsi: sd: provide a new module parameter to set whether SCSI disks support WRITE_SAME_16 by default

[AlexChen <alex.chen@huawei.com>]

When the SCSI device is initialized, check whether it supports
WRITE_SAME_16 or WRITE_SAME_10 in the sd_read_write_same(). If
the back-end storage device does not support queries, it will not set
sdkp->ws16 as 1.

When the WRITE_SAME io is issued through the blkdev_issue_write_same(),
the WRITE_SAME type is set to WRITE_SAME_10 by default in the
sd_setup_write_same_cmnd() since of "sdkp->ws16=0". If the storage device
does not support WRITE_SAME_10, then the SCSI device is set to not support
WRITE_SAME.

Currently, some storage devices do not provide queries for
WRITE_SAME_16/WRITE_SAME_10 support, but they do support WRITE_SAME_16 and
do not support WRITE_SAME_10. So in order for these devices to use
WRITE_SAME, we need a new module parameter to set whether SCSI disks
support WRITE_SAME_16 by default.

Signed-off-by: AlexChen <alex.chen@huawei.com>
---
 drivers/scsi/sd.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 4f7e7b607..ff368701d 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -104,6 +104,9 @@ MODULE_ALIAS_SCSI_DEVICE(TYPE_ZBC);
 #define SD_MINORS	0
 #endif

+static int sd_default_support_ws16;
+module_param(sd_default_support_ws16, int, 0644);
+
 static void sd_config_discard(struct scsi_disk *, unsigned int);
 static void sd_config_write_same(struct scsi_disk *);
 static int  sd_revalidate_disk(struct gendisk *);
@@ -3014,7 +3017,8 @@ static void sd_read_write_same(struct scsi_disk *sdkp, unsigned char *buffer)
 			sdev->no_write_same = 1;
 	}

-	if (scsi_report_opcode(sdev, buffer, SD_BUF_SIZE, WRITE_SAME_16) == 1)
+	if (scsi_report_opcode(sdev, buffer, SD_BUF_SIZE, WRITE_SAME_16) == 1 ||
+			sd_default_support_ws16)
 		sdkp->ws16 = 1;

 	if (scsi_report_opcode(sdev, buffer, SD_BUF_SIZE, WRITE_SAME) == 1)
-- 2.19.1