[SCSI] scsi_error: Refactoring scsi_error to facilitate in synchronous REQUEST_SENSE

 - Drivers/transports that want to send a synchronous REQUEST_SENSE command
   as part of their .queuecommand sequence, have 2 new API's that facilitate
   in doing so and abstract them from scsi-ml internals.

   void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd,
	struct scsi_eh_save *sesci, unsigned char *cmnd,
	int cmnd_size, int sense_bytes)

   Will hijack a command and prepare it for request sense if needed.
   And will save any later needed info into a scsi_eh_save structure.

   void scsi_eh_restore_cmnd(struct scsi_cmnd* scmd,
	struct scsi_eh_save *sesci);

   Will undo any changes done to a command by above function. Making
   it ready for completion.

 - Re-factor scsi_send_eh_cmnd() to use above APIs
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/scsi_error.c

@@ -590,42 +590,23 @@ static void scsi_abort_eh_cmnd(struct scsi_cmnd *scmd)
 }
 
 /**
- * scsi_send_eh_cmnd  - submit a scsi command as part of error recory
+ * scsi_eh_prep_cmnd  - Save a scsi command info as part of error recory
  * @scmd:       SCSI command structure to hijack
+ * @ses:        structure to save restore information
  * @cmnd:       CDB to send. Can be NULL if no new cmnd is needed
  * @cmnd_size:  size in bytes of @cmnd
- * @timeout:    timeout for this request
  * @sense_bytes: size of sense data to copy. or 0 (if != 0 @cmnd is ignored)
  *
- * This function is used to send a scsi command down to a target device
+ * This function is used to save a scsi command information before re-execution
  * as part of the error recovery process.  If @sense_bytes is 0 the command
  * sent must be one that does not transfer any data.  If @sense_bytes != 0
  * @cmnd is ignored and this functions sets up a REQUEST_SENSE command
  * and cmnd buffers to read @sense_bytes into @scmd->sense_buffer.
- *
- * Return value:
- *    SUCCESS or FAILED or NEEDS_RETRY
  **/
-static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
-			     int cmnd_size, int timeout, unsigned sense_bytes)
+void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd, struct scsi_eh_save *ses,
+			unsigned char *cmnd, int cmnd_size, unsigned sense_bytes)
 {
 	struct scsi_device *sdev = scmd->device;
-	struct Scsi_Host *shost = sdev->host;
-	DECLARE_COMPLETION_ONSTACK(done);
-	unsigned long timeleft;
-	unsigned long flags;
-
-	unsigned char old_cmd_len;
-	unsigned char old_cmnd[MAX_COMMAND_SIZE];
-	enum dma_data_direction old_data_direction;
-	unsigned old_bufflen;
-	void *old_buffer;
-	unsigned short old_use_sg;
-	int old_resid;
-	int old_result;
-
-	struct scatterlist sgl;
-	int rtn;
 
 	/*
 	 * We need saved copies of a number of fields - this is because
@@ -634,20 +615,21 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
 	 * we will need to restore these values prior to running the actual
 	 * command.
 	 */
-	old_cmd_len = scmd->cmd_len;
-	memcpy(old_cmnd, scmd->cmnd, sizeof(scmd->cmnd));
-	old_data_direction = scmd->sc_data_direction;
-	old_bufflen = scmd->request_bufflen;
-	old_buffer = scmd->request_buffer;
-	old_use_sg = scmd->use_sg;
-	old_resid = scmd->resid;
-	old_result = scmd->result;
+	ses->cmd_len = scmd->cmd_len;
+	memcpy(ses->cmnd, scmd->cmnd, sizeof(scmd->cmnd));
+	ses->data_direction = scmd->sc_data_direction;
+	ses->bufflen = scmd->request_bufflen;
+	ses->buffer = scmd->request_buffer;
+	ses->use_sg = scmd->use_sg;
+	ses->resid = scmd->resid;
+	ses->result = scmd->result;
 
 	if (sense_bytes) {
 		scmd->request_bufflen = min_t(unsigned,
 		                       sizeof(scmd->sense_buffer), sense_bytes);
-		sg_init_one(&sgl, scmd->sense_buffer, scmd->request_bufflen);
-		scmd->request_buffer = &sgl;
+		sg_init_one(&ses->sense_sgl, scmd->sense_buffer,
+		                                       scmd->request_bufflen);
+		scmd->request_buffer = &ses->sense_sgl;
 		scmd->sc_data_direction = DMA_FROM_DEVICE;
 		scmd->use_sg = 1;
 		memset(scmd->cmnd, 0, sizeof(scmd->cmnd));
@@ -677,7 +659,58 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
 	 * untransferred sense data should be interpreted as being zero.
 	 */
 	memset(scmd->sense_buffer, 0, sizeof(scmd->sense_buffer));
+}
+EXPORT_SYMBOL(scsi_eh_prep_cmnd);
+
+/**
+ * scsi_eh_restore_cmnd  - Restore a scsi command info as part of error recory
+ * @scmd:       SCSI command structure to restore
+ * @ses:        saved information from a coresponding call to scsi_prep_eh_cmnd
+ *
+ * Undo any damage done by above scsi_prep_eh_cmnd().
+ **/
+void scsi_eh_restore_cmnd(struct scsi_cmnd* scmd, struct scsi_eh_save *ses)
+{
+	/*
+	 * Restore original data
+	 */
+	scmd->cmd_len = ses->cmd_len;
+	memcpy(scmd->cmnd, ses->cmnd, sizeof(scmd->cmnd));
+	scmd->sc_data_direction = ses->data_direction;
+	scmd->request_bufflen = ses->bufflen;
+	scmd->request_buffer = ses->buffer;
+	scmd->use_sg = ses->use_sg;
+	scmd->resid = ses->resid;
+	scmd->result = ses->result;
+}
+EXPORT_SYMBOL(scsi_eh_restore_cmnd);
 
+/**
+ * scsi_send_eh_cmnd  - submit a scsi command as part of error recory
+ * @scmd:       SCSI command structure to hijack
+ * @cmnd:       CDB to send
+ * @cmnd_size:  size in bytes of @cmnd
+ * @timeout:    timeout for this request
+ * @sense_bytes: size of sense data to copy or 0
+ *
+ * This function is used to send a scsi command down to a target device
+ * as part of the error recovery process. See also scsi_eh_prep_cmnd() above.
+ *
+ * Return value:
+ *    SUCCESS or FAILED or NEEDS_RETRY
+ **/
+static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
+			     int cmnd_size, int timeout, unsigned sense_bytes)
+{
+	struct scsi_device *sdev = scmd->device;
+	struct Scsi_Host *shost = sdev->host;
+	DECLARE_COMPLETION_ONSTACK(done);
+	unsigned long timeleft;
+	unsigned long flags;
+	struct scsi_eh_save ses;
+	int rtn;
+
+	scsi_eh_prep_cmnd(scmd, &ses, cmnd, cmnd_size, sense_bytes);
 	shost->eh_action = &done;
 
 	spin_lock_irqsave(shost->host_lock, flags);
@@ -721,18 +754,7 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
 		rtn = FAILED;
 	}
 
-
-	/*
-	 * Restore original data
-	 */
-	scmd->cmd_len = old_cmd_len;
-	memcpy(scmd->cmnd, old_cmnd, sizeof(scmd->cmnd));
-	scmd->sc_data_direction = old_data_direction;
-	scmd->request_bufflen = old_bufflen;
-	scmd->request_buffer = old_buffer;
-	scmd->use_sg = old_use_sg;
-	scmd->resid = old_resid;
-	scmd->result = old_result;
+	scsi_eh_restore_cmnd(scmd, &ses);
 	return rtn;
 }
 

include/scsi/scsi_eh.h

 #ifndef _SCSI_SCSI_EH_H
 #define _SCSI_SCSI_EH_H
 
-struct scsi_cmnd;
+#include <scsi/scsi_cmnd.h>
 struct scsi_device;
 struct Scsi_Host;
 
@@ -65,4 +65,25 @@ extern int scsi_get_sense_info_fld(const u8 * sense_buffer, int sb_len,
 
 extern int scsi_reset_provider(struct scsi_device *, int);
 
+struct scsi_eh_save {
+	int result;
+	enum dma_data_direction data_direction;
+	unsigned char cmd_len;
+	unsigned char cmnd[MAX_COMMAND_SIZE];
+
+	void *buffer;
+	unsigned bufflen;
+	unsigned short use_sg;
+	int resid;
+
+	struct scatterlist sense_sgl;
+};
+
+extern void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd,
+		struct scsi_eh_save *ses, unsigned char *cmnd,
+		int cmnd_size, unsigned sense_bytes);
+
+extern void scsi_eh_restore_cmnd(struct scsi_cmnd* scmd,
+		struct scsi_eh_save *ses);
+
 #endif /* _SCSI_SCSI_EH_H */