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Subject[RFC PATCH v2 1/3] scsi: Detailed I/O errors
Date
From: Hannes Reinecke <hare@suse.de>

Instead of just passing 'EIO' for any I/O error we should be
notifying the upper layers with more details about the cause
of this error.

Update the possible I/O errors to:

- ENOLINK: Link failure between host and target
- EIO: Retryable I/O error
- EREMOTEIO: Non-retryable I/O error

'Retryable' in this context means that an I/O error _might_ be
restricted to the I_T_L nexus (vulgo: path), so retrying on another
nexus / path might succeed.

'Non-retryable' means target failure or reservation conflict.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/scsi/scsi_error.c | 24 +++++++++++++++++-------
drivers/scsi/scsi_lib.c | 24 ++++++++++++++++++++++--
include/scsi/scsi.h | 3 +++
3 files changed, 42 insertions(+), 9 deletions(-)
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 824b8fc..48fdd85 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -223,7 +223,7 @@ static inline void scsi_eh_prt_fail_stats(struct Scsi_Host *shost,
* @scmd: Cmd to have sense checked.
*
* Return value:
- * SUCCESS or FAILED or NEEDS_RETRY
+ * SUCCESS or FAILED or NEEDS_RETRY or TARGET_ERROR
*
* Notes:
* When a deferred error is detected the current command has
@@ -326,17 +326,19 @@ static int scsi_check_sense(struct scsi_cmnd *scmd)
*/
return SUCCESS;

- /* these three are not supported */
+ /* these are not supported */
case COPY_ABORTED:
case VOLUME_OVERFLOW:
case MISCOMPARE:
- return SUCCESS;
+ case BLANK_CHECK:
+ case DATA_PROTECT:
+ return TARGET_ERROR;

case MEDIUM_ERROR:
if (sshdr.asc == 0x11 || /* UNRECOVERED READ ERR */
sshdr.asc == 0x13 || /* AMNF DATA FIELD */
sshdr.asc == 0x14) { /* RECORD NOT FOUND */
- return SUCCESS;
+ return TARGET_ERROR;
}
return NEEDS_RETRY;

@@ -344,11 +346,9 @@ static int scsi_check_sense(struct scsi_cmnd *scmd)
if (scmd->device->retry_hwerror)
return ADD_TO_MLQUEUE;
else
- return SUCCESS;
+ return TARGET_ERROR;

case ILLEGAL_REQUEST:
- case BLANK_CHECK:
- case DATA_PROTECT:
default:
return SUCCESS;
}
@@ -809,6 +809,7 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
case SUCCESS:
case NEEDS_RETRY:
case FAILED:
+ case TARGET_ERROR:
break;
case ADD_TO_MLQUEUE:
rtn = NEEDS_RETRY;
@@ -1502,6 +1503,14 @@ int scsi_decide_disposition(struct scsi_cmnd *scmd)
rtn = scsi_check_sense(scmd);
if (rtn == NEEDS_RETRY)
goto maybe_retry;
+ else if (rtn == TARGET_ERROR) {
+ /*
+ * Need to modify host byte to signal a
+ * permanent target failure
+ */
+ scmd->result |= (DID_TARGET_FAILURE << 16);
+ rtn = SUCCESS;
+ }
/* if rtn == FAILED, we have no sense information;
* returning FAILED will wake the error handler thread
* to collect the sense and redo the decide
@@ -1519,6 +1528,7 @@ int scsi_decide_disposition(struct scsi_cmnd *scmd)
case RESERVATION_CONFLICT:
sdev_printk(KERN_INFO, scmd->device,
"reservation conflict\n");
+ scmd->result |= (DID_TARGET_FAILURE << 16);
return SUCCESS; /* causes immediate i/o error */
default:
return FAILED;
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index eafeeda..4da6459 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -667,6 +667,26 @@ void scsi_release_buffers(struct scsi_cmnd *cmd)
}
EXPORT_SYMBOL(scsi_release_buffers);

+static int __scsi_error_from_host_byte(struct scsi_cmnd *cmd, int result)
+{
+ int error = 0;
+
+ switch(host_byte(result)) {
+ case DID_TRANSPORT_FAILFAST:
+ error = -ENOLINK;
+ break;
+ case DID_TARGET_FAILURE:
+ cmd->result |= (DID_OK << 16);
+ error = -EREMOTEIO;
+ break;
+ default:
+ error = -EIO;
+ break;
+ }
+
+ return error;
+}
+
/*
* Function: scsi_io_completion()
*
@@ -737,7 +757,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
req->sense_len = len;
}
if (!sense_deferred)
- error = -EIO;
+ error = __scsi_error_from_host_byte(cmd, result);
}

req->resid_len = scsi_get_resid(cmd);
@@ -796,7 +816,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
return;

- error = -EIO;
+ error = __scsi_error_from_host_byte(cmd, result);

if (host_byte(result) == DID_RESET) {
/* Third party bus reset or reset for error recovery
diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
index 216af85..73d27d9 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -405,6 +405,8 @@ static inline int scsi_is_wlun(unsigned int lun)
* recover the link. Transport class will
* retry or fail IO */
#define DID_TRANSPORT_FAILFAST 0x0f /* Transport class fastfailed the io */
+#define DID_TARGET_FAILURE 0x10 /* Permanent target failure, do not retry on
+ * other paths */
#define DRIVER_OK 0x00 /* Driver status */

/*
@@ -434,6 +436,7 @@ static inline int scsi_is_wlun(unsigned int lun)
#define TIMEOUT_ERROR 0x2007
#define SCSI_RETURN_NOT_HANDLED 0x2008
#define FAST_IO_FAIL 0x2009
+#define TARGET_ERROR 0x200A

/*
* Midlevel queue return values.
--
1.7.2.3


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