[PATCH v2 08/10] scsi: Add error codes for internal scsi-ml use

[Mike Christie <michael.christie@xxxxxxxxxx>]

If a driver returns:

DID_TARGET_FAILURE
DID_NEXUS_FAILURE
DID_ALLOC_FAILURE
DID_MEDIUM_ERROR

we hit a couple bugs:

1. The SCSI error handler runs because scsi_decide_disposition has no
case statements for them and we return FAILED.

2. For SG IO the userspace app gets a success status instead of failed,
because scsi_result_to_blk_status clears those errors.

This patch adds a new internal error code byte for use by scsi-ml. It
will be used instead of the above error codes, so we don't have to play
that clearing the host code game in scsi_result_to_blk_status and
drivers cannot accidentally use them.

The next patch will then remove the internal users of the above codes and
convert us to use the new ones.

Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 drivers/scsi/scsi_error.c |  5 +++++
 drivers/scsi/scsi_lib.c   | 22 ++++++++++++++++++++++
 drivers/scsi/scsi_priv.h  | 11 +++++++++++
 3 files changed, 38 insertions(+)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 448748e3fba5..d09b9ba1518c 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -514,6 +514,11 @@ static void scsi_report_sense(struct scsi_device *sdev,
 	}
 }
 
+static inline void set_scsi_ml_byte(struct scsi_cmnd *cmd, u8 status)
+{
+	cmd->result = (cmd->result & 0xffff00ff) | (status << 8);
+}
+
 /**
  * scsi_check_sense - Examine scsi cmd sense
  * @scmd:	Cmd to have sense checked.
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 4dbd29ab1dcc..92b8c050697e 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -576,6 +576,11 @@ static bool scsi_end_request(struct request *req, blk_status_t error,
 	return false;
 }
 
+static inline u8 get_scsi_ml_byte(int result)
+{
+	return (result >> 8) & 0xff;
+}
+
 /**
  * scsi_result_to_blk_status - translate a SCSI result code into blk_status_t
  * @cmd:	SCSI command
@@ -586,6 +591,23 @@ static bool scsi_end_request(struct request *req, blk_status_t error,
  */
 static blk_status_t scsi_result_to_blk_status(struct scsi_cmnd *cmd, int result)
 {
+	/*
+	 * Check the scsi-ml byte first in case we converted a host or status
+	 * byte.
+	 */
+	switch (get_scsi_ml_byte(result)) {
+	case SCSIML_STAT_OK:
+		break;
+	case SCSIML_STAT_RESV_CONFLICT:
+		return BLK_STS_NEXUS;
+	case SCSIML_STAT_NOSPC:
+		return BLK_STS_NOSPC;
+	case SCSIML_STAT_MED_ERROR:
+		return BLK_STS_MEDIUM;
+	case SCSIML_STAT_TGT_FAILURE:
+		return BLK_STS_TARGET;
+	}
+
 	switch (host_byte(result)) {
 	case DID_OK:
 		if (scsi_status_is_good(result))
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index 429663bd78ec..2b9e0559ddcb 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -18,6 +18,17 @@ struct scsi_nl_hdr;
 
 #define SCSI_CMD_RETRIES_NO_LIMIT -1
 
+/*
+ * Error codes used by scsi-ml internally. These must not be used by drivers.
+ */
+enum scsi_ml_status {
+	SCSIML_STAT_OK			= 0x00,
+	SCSIML_STAT_RESV_CONFLICT	= 0x01,	/* Reservation conflict */
+	SCSIML_STAT_NOSPC		= 0x02,	/* Space allocation on the dev failed */
+	SCSIML_STAT_MED_ERROR		= 0x03,	/* Medium error */
+	SCSIML_STAT_TGT_FAILURE		= 0x04,	/* Permanent target failure */
+};
+
 /*
  * Scsi Error Handler Flags
  */
-- 
2.18.2