[PATCH v4 06/29] scsi: core: Extend the scsi_execute_cmd() functionality

[Bart Van Assche <bvanassche@acm.org>]

Make the @cmd argument optional. Add .init_cmd() and .copy_result()
callbacks in struct scsi_exec_args. Support allocating from a specific
hardware queue. This patch prepares for submitting reserved commands
with scsi_execute_cmd().

Cc: John Garry <john.g.garry@oracle.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi_lib.c    | 28 +++++++++++++++++++++++++---
 include/scsi/scsi_cmnd.h   |  2 ++
 include/scsi/scsi_device.h | 37 +++++++++++++++++++++++++++++--------
 3 files changed, 56 insertions(+), 11 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 5e636e015352..022cd454d658 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -308,7 +308,10 @@ int scsi_execute_cmd(struct scsi_device *sdev, const unsigned char *cmd,
 		return -EINVAL;
 
 retry:
-	req = scsi_alloc_request(sdev->request_queue, opf, args->req_flags);
+	req = args->specify_hctx ?
+		scsi_alloc_request_hctx(sdev->request_queue, opf,
+					args->req_flags, args->hctx_idx) :
+		scsi_alloc_request(sdev->request_queue, opf, args->req_flags);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
@@ -318,8 +321,12 @@ int scsi_execute_cmd(struct scsi_device *sdev, const unsigned char *cmd,
 			goto out;
 	}
 	scmd = blk_mq_rq_to_pdu(req);
-	scmd->cmd_len = COMMAND_SIZE(cmd[0]);
-	memcpy(scmd->cmnd, cmd, scmd->cmd_len);
+	if (cmd) {
+		scmd->cmd_len = COMMAND_SIZE(cmd[0]);
+		memcpy(scmd->cmnd, cmd, scmd->cmd_len);
+	}
+	if (args->init_cmd)
+		args->init_cmd(scmd, args);
 	scmd->allowed = ml_retries;
 	scmd->flags |= args->scmd_flags;
 	req->timeout = timeout;
@@ -353,6 +360,9 @@ int scsi_execute_cmd(struct scsi_device *sdev, const unsigned char *cmd,
 				     args->sshdr);
 
 	ret = scmd->result;
+	if (ret == 0 && args->copy_result)
+		args->copy_result(scmd, args);
+
  out:
 	blk_mq_free_request(req);
 
@@ -1247,6 +1257,18 @@ struct request *scsi_alloc_request(struct request_queue *q, blk_opf_t opf,
 }
 EXPORT_SYMBOL_GPL(scsi_alloc_request);
 
+struct request *scsi_alloc_request_hctx(struct request_queue *q, blk_opf_t opf,
+			blk_mq_req_flags_t flags, unsigned int hctx_idx)
+{
+	struct request *rq;
+
+	rq = blk_mq_alloc_request_hctx(q, opf, flags, hctx_idx);
+	if (!IS_ERR(rq))
+		scsi_initialize_rq(rq);
+	return rq;
+}
+EXPORT_SYMBOL_GPL(scsi_alloc_request_hctx);
+
 /*
  * Only called when the request isn't completed by SCSI, and not freed by
  * SCSI
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 8ecfb94049db..a4cb836809df 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -396,5 +396,7 @@ extern void scsi_build_sense(struct scsi_cmnd *scmd, int desc,
 
 struct request *scsi_alloc_request(struct request_queue *q, blk_opf_t opf,
 				   blk_mq_req_flags_t flags);
+struct request *scsi_alloc_request_hctx(struct request_queue *q, blk_opf_t opf,
+			blk_mq_req_flags_t flags, unsigned int hctx_idx);
 
 #endif /* _SCSI_SCSI_CMND_H */
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 3846f5dfc51c..2b2dc08962a2 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -541,15 +541,36 @@ struct scsi_failures {
 	struct scsi_failure *failure_definitions;
 };
 
-/* Optional arguments to scsi_execute_cmd */
+/**
+ * struct scsi_exec_args - Optional arguments to scsi_execute_cmd()
+ * @init_cmd: called before the command is executed.
+ * @copy_result: called after the command has been executed.
+ * @sense: sense buffer.
+ * @sense_len: sense buffer len
+ * @sshdr: decoded sense header
+ * @req_flags: BLK_MQ_REQ flags
+ * @scmd_flags: SCMD flags.
+ * @resid: residual length.
+ * @failures: which failures to retry.
+ * @specify_hctx: call scsi_alloc_request_hctx() if %true or
+	scsi_alloc_request() otherwise.
+ * @hctx_idx: Passed as fourth argument for scsi_alloc_request_hctx() if
+	@specify_hctx is %true.
+ */
 struct scsi_exec_args {
-	unsigned char *sense;		/* sense buffer */
-	unsigned int sense_len;		/* sense buffer len */
-	struct scsi_sense_hdr *sshdr;	/* decoded sense header */
-	blk_mq_req_flags_t req_flags;	/* BLK_MQ_REQ flags */
-	int scmd_flags;			/* SCMD flags */
-	int *resid;			/* residual length */
-	struct scsi_failures *failures;	/* failures to retry */
+	int (*init_cmd)(struct scsi_cmnd *cmd,
+			const struct scsi_exec_args *args);
+	void (*copy_result)(struct scsi_cmnd *cmd,
+			    const struct scsi_exec_args *args);
+	unsigned char *sense;
+	unsigned int sense_len;
+	struct scsi_sense_hdr *sshdr;
+	blk_mq_req_flags_t req_flags;
+	int scmd_flags;
+	int *resid;
+	struct scsi_failures *failures;
+	bool specify_hctx;
+	int hctx_idx;
 };
 
 int scsi_execute_cmd(struct scsi_device *sdev, const unsigned char *cmd,