[SCSI] Add detailed SCSI I/O errors

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
- EBADE: I/O error restricted to the I_T_L nexus

'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' in general refers to a target failure, so this
error will always be generated regardless of the I_T_L nexus
it was send on.

I/O errors restricted to the I_T_L nexus might be retried
on another nexus / path, but they should _not_ be queued
if no paths are available.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

3 files changed, 48 insertions, 9 deletions

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 45c75649b9e0..991de3c15cfc 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;
         }
@@ -787,6 +787,7 @@ 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;
@@ -1469,6 +1470,14 @@ 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
@@ -1486,6 +1495,7 @@ int scsi_decide_disposition(struct scsi_cmnd *scmd)
         case RESERVATION_CONFLICT:
                 sdev_printk(KERN_INFO, scmd->device,
                             "reservation conflict\n");
+                scmd->result |= (DID_NEXUS_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 9045c52abd25..8d4ef8efa3cd 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -667,6 +667,30 @@ 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;
+        case DID_NEXUS_FAILURE:
+                cmd->result |= (DID_OK << 16);
+                error = -EBADE;
+                break;
+        default:
+                error = -EIO;
+                break;
+        }
+
+        return error;
+}
+
 /*
  * Function:    scsi_io_completion()
  *
@@ -737,7 +761,7 @@ 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 +820,7 @@ 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 648d23358038..ead8dd054480 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -434,6 +434,10 @@ 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 DID_NEXUS_FAILURE 0x11  /* Permanent nexus failure, retry on other
+                                 * paths might yield different results */
 #define DRIVER_OK       0x00    /* Driver status                           */
 
 /*
@@ -463,6 +467,7 @@ 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.