[PATCH V2] scsi: add a new flag 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
support, and only WRITE_SAME_16 is supported, not WRITE_SAME_10.
Therefore, we need to provide a new flag for these storage devices. When
initializing these devices, we will no longer query for support for
WRITE_SAME_16 in the sd_read_write_same(), but set these SCSI disks to
support WRITE_SAME_16 by default. In that way, we can add
'vendor:product:flag' to the module parameter 'dev_flags' for these
storage devices.

Signed-off-by: AlexChen <alex.chen@huawei.com>
---
 drivers/scsi/sd.c           | 4 +++-
 include/scsi/scsi_devinfo.h | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 4f7e7b607..a208ba5b5 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -68,6 +68,7 @@
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_ioctl.h>
 #include <scsi/scsicam.h>
+#include <scsi/scsi_devinfo.h>

 #include "sd.h"
 #include "scsi_priv.h"
@@ -3014,7 +3015,8 @@ 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 ||
+			sdev->sdev_bflags & BLIST_SUPPORT_WS16)
 		sdkp->ws16 = 1;

 	if (scsi_report_opcode(sdev, buffer, SD_BUF_SIZE, WRITE_SAME) == 1)
diff --git a/include/scsi/scsi_devinfo.h b/include/scsi/scsi_devinfo.h
index 3fdb322d4..da70d4795 100644
--- a/include/scsi/scsi_devinfo.h
+++ b/include/scsi/scsi_devinfo.h
@@ -67,8 +67,10 @@
 #define BLIST_RETRY_ITF		((__force blist_flags_t)(1ULL << 32))
 /* Always retry ABORTED_COMMAND with ASC 0xc1 */
 #define BLIST_RETRY_ASC_C1	((__force blist_flags_t)(1ULL << 33))
+/* support for write_same_16, no need to query */
+#define BLIST_SUPPORT_WS16      ((__force blist_flags_t)(1ULL << 34))

-#define __BLIST_LAST_USED BLIST_RETRY_ASC_C1
+#define __BLIST_LAST_USED BLIST_SUPPORT_WS16

 #define __BLIST_HIGH_UNUSED (~(__BLIST_LAST_USED | \
 			       (__force blist_flags_t) \
-- 
2.19.1