[PATCH v6 02/35] scsi: Allow passthrough to override what errors to retry

[Mike Christie <michael.christie@oracle.com>]

For passthrough, we don't retry any error we get a check condition for.
This results in a lot of callers driving their own retries for those types
of errors and retrying all errors, and there has been a request to retry
specific host byte errors.

This adds the core code to allow passthrough users to specify what errors
they want scsi-ml to retry for them. We can then convert users to drop
their sense parsing and retry handling.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
---
 drivers/scsi/scsi_error.c | 82 +++++++++++++++++++++++++++++++++++++++
 drivers/scsi/scsi_lib.c   |  1 +
 include/scsi/scsi_cmnd.h  | 26 ++++++++++++-
 3 files changed, 108 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 994b7472fc56..77d7ad07645a 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1829,6 +1829,82 @@ bool scsi_noretry_cmd(struct scsi_cmnd *scmd)
 	return false;
 }
 
+/**
+ * scsi_check_passthrough - Determine if passthrough scsi_cmnd needs a retry.
+ * @scmd: scsi_cmnd to check.
+ *
+ * Return value:
+ *	SCSI_RETURN_NOT_HANDLED - if the caller should process the command
+ *	because there is no error or the passthrough user wanted the default
+ *	error processing.
+ *	SUCCESS, FAILED or NEEDS_RETRY - if this function has determined the
+ *	command should be completed, go through the error handler due to
+ *	missing sense or should be retried.
+ */
+static enum scsi_disposition scsi_check_passthrough(struct scsi_cmnd *scmd)
+{
+	struct scsi_failure *failure;
+	struct scsi_sense_hdr sshdr;
+	enum scsi_disposition ret;
+	enum sam_status status;
+
+	if (!scmd->result || !scmd->failures)
+		return SCSI_RETURN_NOT_HANDLED;
+
+	for (failure = scmd->failures; failure->result; failure++) {
+		if (failure->result == SCMD_FAILURE_RESULT_ANY)
+			goto maybe_retry;
+
+		if (host_byte(scmd->result) &&
+		    host_byte(scmd->result) == host_byte(failure->result))
+			goto maybe_retry;
+
+		status = get_status_byte(scmd);
+		if (!status)
+			continue;
+
+		if (failure->result == SCMD_FAILURE_STAT_ANY &&
+		    !scsi_status_is_good(scmd->result))
+			goto maybe_retry;
+
+		if (status != __get_status_byte(failure->result))
+			continue;
+
+		if (__get_status_byte(failure->result) !=
+		    SAM_STAT_CHECK_CONDITION ||
+		    failure->sense == SCMD_FAILURE_SENSE_ANY)
+			goto maybe_retry;
+
+		ret = scsi_start_sense_processing(scmd, &sshdr);
+		if (ret == NEEDS_RETRY)
+			goto maybe_retry;
+		else if (ret != SUCCESS)
+			return ret;
+
+		if (failure->sense != sshdr.sense_key)
+			continue;
+
+		if (failure->asc == SCMD_FAILURE_ASC_ANY)
+			goto maybe_retry;
+
+		if (failure->asc != sshdr.asc)
+			continue;
+
+		if (failure->ascq == SCMD_FAILURE_ASCQ_ANY ||
+		    failure->ascq == sshdr.ascq)
+			goto maybe_retry;
+	}
+
+	return SCSI_RETURN_NOT_HANDLED;
+
+maybe_retry:
+	if (failure->allowed == SCMD_FAILURE_NO_LIMIT ||
+	    ++failure->retries <= failure->allowed)
+		return NEEDS_RETRY;
+
+	return SUCCESS;
+}
+
 /**
  * scsi_decide_disposition - Disposition a cmd on return from LLD.
  * @scmd:	SCSI cmd to examine.
@@ -1857,6 +1933,12 @@ enum scsi_disposition scsi_decide_disposition(struct scsi_cmnd *scmd)
 		return SUCCESS;
 	}
 
+	if (blk_rq_is_passthrough(scsi_cmd_to_rq(scmd))) {
+		rtn = scsi_check_passthrough(scmd);
+		if (rtn != SCSI_RETURN_NOT_HANDLED)
+			return rtn;
+	}
+
 	/*
 	 * first check the host byte, to see if there is anything in there
 	 * that would indicate what we need to do.
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index ec890865abae..fc1560981a03 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1128,6 +1128,7 @@ static void scsi_initialize_rq(struct request *rq)
 	init_rcu_head(&cmd->rcu);
 	cmd->jiffies_at_alloc = jiffies;
 	cmd->retries = 0;
+	cmd->failures = NULL;
 }
 
 struct request *scsi_alloc_request(struct request_queue *q, blk_opf_t opf,
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index c2cb5f69635c..016a371715b7 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -66,6 +66,23 @@ enum scsi_cmnd_submitter {
 	SUBMITTED_BY_SCSI_RESET_IOCTL = 2,
 } __packed;
 
+#define SCMD_FAILURE_RESULT_ANY	0x7fffffff
+#define SCMD_FAILURE_STAT_ANY	0xff
+#define SCMD_FAILURE_SENSE_ANY	0xff
+#define SCMD_FAILURE_ASC_ANY	0xff
+#define SCMD_FAILURE_ASCQ_ANY	0xff
+#define SCMD_FAILURE_NO_LIMIT	-1
+
+struct scsi_failure {
+	int result;
+	u8 sense;
+	u8 asc;
+	u8 ascq;
+
+	s8 allowed;
+	s8 retries;
+};
+
 struct scsi_cmnd {
 	struct scsi_device *device;
 	struct list_head eh_entry; /* entry for the host eh_abort_list/eh_cmd_q */
@@ -86,6 +103,8 @@ struct scsi_cmnd {
 
 	int retries;
 	int allowed;
+	/* optional array of failures that passthrough users want retried */
+	struct scsi_failure *failures;
 
 	unsigned char prot_op;
 	unsigned char prot_type;
@@ -331,9 +350,14 @@ static inline void set_status_byte(struct scsi_cmnd *cmd, char status)
 	cmd->result = (cmd->result & 0xffffff00) | status;
 }
 
+static inline u8 __get_status_byte(int result)
+{
+	return result & 0xff;
+}
+
 static inline u8 get_status_byte(struct scsi_cmnd *cmd)
 {
-	return cmd->result & 0xff;
+	return __get_status_byte(cmd->result);
 }
 
 static inline void set_host_byte(struct scsi_cmnd *cmd, char status)
-- 
2.25.1