[v6,3/7] scsi_io_completion_nz_result: function added

Commit Message

Douglas Gilbert June 23, 2018, 10:22 a.m. UTC

Break out several intertwined paths when cmd->result is non zero and
place them in the scsi_io_completion_nz_result helper function. The
logic is not changed.

Signed-off-by: Douglas Gilbert <[e-mail]>
Reviewed-by: Johannes Thumshirn <[e-mail]>
Reviewed-by: Bart Van Assche <[e-mail]>
---
A reviewer requested the original helper function's two return values
be reduced to one: the blk_stat variable. This required a hack to
differentiate the default setting of blk_stat (BLK_STS_OK) from the case
when the helper assigns BLK_STS_OK as the return value. The hack was to
return the otherwise unused BLK_STS_NOTSUPP value as an indication that
the helper didn't change anything. That hack was judged by another
reviewer to be worse that the "two return values" ugliness it was
trying to address. So back to the original "two return values" solution.

 drivers/scsi/scsi_lib.c | 132 +++++++++++++++++++++++-----------------
 1 file changed, 75 insertions(+), 57 deletions(-)

Comments

Hannes Reinecke June 26, 2018, 5:17 a.m. UTC | #1

On 06/23/2018 12:22 PM, Douglas Gilbert wrote:
> Break out several intertwined paths when cmd->result is non zero and
> place them in the scsi_io_completion_nz_result helper function. The
> logic is not changed.
> 
> Signed-off-by: Douglas Gilbert <[e-mail]>
> Reviewed-by: Johannes Thumshirn <[e-mail]>
> Reviewed-by: Bart Van Assche <[e-mail]>
> ---
> A reviewer requested the original helper function's two return values
> be reduced to one: the blk_stat variable. This required a hack to
> differentiate the default setting of blk_stat (BLK_STS_OK) from the case
> when the helper assigns BLK_STS_OK as the return value. The hack was to
> return the otherwise unused BLK_STS_NOTSUPP value as an indication that
> the helper didn't change anything. That hack was judged by another
> reviewer to be worse that the "two return values" ugliness it was
> trying to address. So back to the original "two return values" solution.
> 
>   drivers/scsi/scsi_lib.c | 132 +++++++++++++++++++++++-----------------
>   1 file changed, 75 insertions(+), 57 deletions(-)
> 
Still looks ugly, but then it's only a helper function.

Reviewed-by: Hannes Reinecke <[e-mail]>

Cheers,

Hannes

Patch

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 1da1ff46c496..02892408962b 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -761,6 +761,79 @@  static blk_status_t scsi_result_to_blk_status(struct scsi_cmnd *cmd, int result)
 	}
 }
 
+/*
+ * Helper for scsi_io_completion() when cmd->result is non-zero. Returns a
+ * new result that may suppress further error checking. Also modifies
+ * *blk_statp in some cases.
+ */
+static int scsi_io_completion_nz_result(struct scsi_cmnd *cmd, int result,
+					blk_status_t *blk_statp)
+{
+	bool sense_valid;
+	bool sense_current = true;	/* false implies "deferred sense" */
+	struct request *req = cmd->request;
+	struct scsi_sense_hdr sshdr;
+
+	sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
+	if (sense_valid)
+		sense_current = !scsi_sense_is_deferred(&sshdr);
+
+	if (blk_rq_is_passthrough(req)) {
+		if (sense_valid) {
+			/*
+			 * SG_IO wants current and deferred errors
+			 */
+			scsi_req(req)->sense_len =
+				min(8 + cmd->sense_buffer[7],
+				    SCSI_SENSE_BUFFERSIZE);
+		}
+		if (sense_current)
+			*blk_statp = scsi_result_to_blk_status(cmd, result);
+	} else if (blk_rq_bytes(req) == 0 && sense_current) {
+		/*
+		 * Flush commands do not transfers any data, and thus cannot use
+		 * good_bytes != blk_rq_bytes(req) as the signal for an error.
+		 * This sets *blk_statp explicitly for the problem case.
+		 */
+		*blk_statp = scsi_result_to_blk_status(cmd, result);
+	}
+	/*
+	 * Recovered errors need reporting, but they're always treated as
+	 * success, so fiddle the result code here.  For passthrough requests
+	 * we already took a copy of the original into sreq->result which
+	 * is what gets returned to the user
+	 */
+	if (sense_valid && (sshdr.sense_key == RECOVERED_ERROR)) {
+		bool do_print = true;
+		/*
+		 * if ATA PASS-THROUGH INFORMATION AVAILABLE [0x0, 0x1d]
+		 * skip print since caller wants ATA registers. Only occurs
+		 * on SCSI ATA PASS_THROUGH commands when CK_COND=1
+		 */
+		if ((sshdr.asc == 0x0) && (sshdr.ascq == 0x1d))
+			do_print = false;
+		else if (req->rq_flags & RQF_QUIET)
+			do_print = false;
+		if (do_print)
+			scsi_print_sense(cmd);
+		result = 0;
+		/* for passthrough, *blk_statp may be set */
+		*blk_statp = BLK_STS_OK;
+	}
+	/*
+	 * Another corner case: the SCSI status byte is non-zero but 'good'.
+	 * Example: PRE-FETCH command returns SAM_STAT_CONDITION_MET when
+	 * it is able to fit nominated LBs in its cache (and SAM_STAT_GOOD
+	 * if it can't fit). Treat SAM_STAT_CONDITION_MET and the related
+	 * intermediate statuses (both obsolete in SAM-4) as good.
+	 */
+	if (status_byte(result) && scsi_status_is_good(result)) {
+		result = 0;
+		*blk_statp = BLK_STS_OK;
+	}
+	return result;
+}
+
 /*
  * Function:    scsi_io_completion()
  *
@@ -804,26 +877,14 @@  void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	      ACTION_DELAYED_RETRY} action;
 	unsigned long wait_for = (cmd->allowed + 1) * req->timeout;
 
-	if (result) {
+	if (result) {	/* does not necessarily mean there is an error */
 		sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
 		if (sense_valid)
 			sense_current = !scsi_sense_is_deferred(&sshdr);
+		result = scsi_io_completion_nz_result(cmd, result, &blk_stat);
 	}
 
 	if (blk_rq_is_passthrough(req)) {
-		if (result) {
-			if (sense_valid) {
-				/*
-				 * SG_IO wants current and deferred errors
-				 */
-				scsi_req(req)->sense_len =
-					min(8 + cmd->sense_buffer[7],
-					    SCSI_SENSE_BUFFERSIZE);
-			}
-			if (sense_current)
-				blk_stat = scsi_result_to_blk_status(cmd,
-								       result);
-		}
 		/*
 		 * scsi_result_to_blk_status may have reset the host_byte
 		 */
@@ -841,13 +902,6 @@  void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 				BUG();
 			return;
 		}
-	} else if (blk_rq_bytes(req) == 0 && result && sense_current) {
-		/*
-		 * Flush commands do not transfers any data, and thus cannot use
-		 * good_bytes != blk_rq_bytes(req) as the signal for an error.
-		 * This sets blk_stat explicitly for the problem case.
-		 */
-		blk_stat = scsi_result_to_blk_status(cmd, result);
 	}
 
 	/* no bidi support for !blk_rq_is_passthrough yet */
@@ -861,42 +915,6 @@  void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		"%u sectors total, %d bytes done.\n",
 		blk_rq_sectors(req), good_bytes));
 
-	/*
-	 * Recovered errors need reporting, but they're always treated as
-	 * success, so fiddle the result code here.  For passthrough requests
-	 * we already took a copy of the original into sreq->result which
-	 * is what gets returned to the user
-	 */
-	if (sense_valid && (sshdr.sense_key == RECOVERED_ERROR)) {
-		bool do_print = true;
-
-		/*
-		 * If ATA PASS-THROUGH INFORMATION AVAILABLE skip
-		 * print since caller wants ATA registers. Only occurs on
-		 * SCSI ATA PASS_THROUGH commands when CK_COND=1
-		 */
-		if ((sshdr.asc == 0x0) && (sshdr.ascq == 0x1d))
-			do_print = false;
-		else if (req->rq_flags & RQF_QUIET)
-			do_print = false;
-		if (do_print)
-			scsi_print_sense(cmd);
-		result = 0;
-		/* for passthrough, blk_stat may be set */
-		blk_stat = BLK_STS_OK;
-	}
-	/*
-	 * Another corner case: the SCSI status byte is non-zero but 'good'.
-	 * Example: PRE-FETCH command returns SAM_STAT_CONDITION_MET when
-	 * it is able to fit nominated LBs in its cache (and SAM_STAT_GOOD
-	 * if it can't fit). Treat SAM_STAT_CONDITION_MET and the related
-	 * intermediate statuses (both obsolete in SAM-4) as good.
-	 */
-	if (status_byte(result) && scsi_status_is_good(result)) {
-		result = 0;
-		blk_stat = BLK_STS_OK;
-	}
-
 	/*
 	 * Next deal with any sectors which we were able to correctly
 	 * handle. Failed, zero length commands always need to drop down