[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>

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 45c7564..991de3c 100644 (file)
--- 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 9045c52..8d4ef8e 100644 (file)
--- 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 648d233..ead8dd0 100644 (file)
--- 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.