scsi: core: Clear driver private data when retrying request

JIRA: https://issues.redhat.com/browse/RHEL-86156
Upstream Status: From upstream linux mainline
Conflicts: Merge differences due to various commits not present in RHEL 9
	   which only affected the portion of this patch that removed the
	   memset() of the per-cmd private drivate data from the function
	   scsi_init_command() -- RHEL 9 still avoids zeroing the scsi_req
	   but this does not affect the memset() added to scsi_queue_rq().

After commit 1bad6c4 ("scsi: zero per-cmd private driver data for each
MQ I/O"), the xen-scsifront/virtio_scsi/snic drivers all removed code that
explicitly zeroed driver-private command data.

In combination with commit 464a00c ("scsi: core: Kill DRIVER_SENSE"),
after virtio_scsi performs a capacity expansion, the first request will
return a unit attention to indicate that the capacity has changed. And then
the original command is retried. As driver-private command data was not
cleared, the request would return UA again and eventually time out and fail.

Zero driver-private command data when a request is retried.

Fixes: f7de50d ("scsi: xen-scsifront: Remove code that zeroes driver-private command data")
Fixes: c2bb873 ("scsi: virtio_scsi: Remove code that zeroes driver-private command data")
Fixes: c3006a9 ("scsi: snic: Remove code that zeroes driver-private command data")
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20250217021628.2929248-1-yebin@huaweicloud.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
(cherry picked from commit dce5c4a)
Signed-off-by: Ewan D. Milne <emilne@redhat.com>

Author: Ewan D. Milne

drivers/scsi/scsi_lib.c

@@ -1295,13 +1295,9 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
 	retries = cmd->retries;
 	in_flight = test_bit(SCMD_STATE_INFLIGHT, &cmd->state);
 	/*
-	 * Zero out the cmd, except for the embedded scsi_request. Only clear
-	 * the driver-private command data if the LLD does not supply a
-	 * function to initialize that data.
+	 * Zero out the cmd, except for the embedded scsi_request.
 	 */
 	to_clear = sizeof(*cmd) - sizeof(cmd->req);
-	if (!dev->host->hostt->init_cmd_priv)
-		to_clear += dev->host->hostt->cmd_size;
 	memset((char *)cmd + sizeof(cmd->req), 0, to_clear);
 
 	cmd->device = dev;
@@ -1867,6 +1863,13 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 	if (!scsi_host_queue_ready(q, shost, sdev, cmd))
 		goto out_dec_target_busy;
 
+	/*
+	 * Only clear the driver-private command data if the LLD does not supply
+	 * a function to initialize that data.
+	 */
+	if (shost->hostt->cmd_size && !shost->hostt->init_cmd_priv)
+		memset(cmd + 1, 0, shost->hostt->cmd_size);
+
 	if (!(req->rq_flags & RQF_DONTPREP)) {
 		ret = scsi_prepare_cmd(req);
 		if (ret != BLK_STS_OK)