[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>

1 files changed, 26 insertions, 2 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 9045c52..8d4ef8e 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