block: introduce new block status code type

Currently we use nornal Linux errno values in the block layer, and while
we accept any error a few have overloaded magic meanings.  This patch
instead introduces a new  blk_status_t value that holds block layer specific
status codes and explicitly explains their meaning.  Helpers to convert from
and to the previous special meanings are provided for now, but I suspect
we want to get rid of them in the long run - those drivers that have a
errno input (e.g. networking) usually get errnos that don't know about
the special block layer overloads, and similarly returning them to userspace
will usually return somethings that strictly speaking isn't correct
for file system operations, but that's left as an exercise for later.

For now the set of errors is a very limited set that closely corresponds
to the previous overloaded errno values, but there is some low hanging
fruite to improve it.

blk_status_t (ab)uses the sparse __bitwise annotations to allow for sparse
typechecking, so that we can easily catch places passing the wrong values.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 17 insertions, 34 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 884aaa84c2dd..67a67191520f 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -635,7 +635,7 @@ static void scsi_release_bidi_buffers(struct scsi_cmnd *cmd)
 	cmd->request->next_rq->special = NULL;
 }
 
-static bool scsi_end_request(struct request *req, int error,
+static bool scsi_end_request(struct request *req, blk_status_t error,
 		unsigned int bytes, unsigned int bidi_bytes)
 {
 	struct scsi_cmnd *cmd = req->special;
@@ -694,45 +694,28 @@ static bool scsi_end_request(struct request *req, int error,
  * @cmd:	SCSI command (unused)
  * @result:	scsi error code
  *
- * Translate SCSI error code into standard UNIX errno.
- * Return values:
- * -ENOLINK	temporary transport failure
- * -EREMOTEIO	permanent target failure, do not retry
- * -EBADE	permanent nexus failure, retry on other path
- * -ENOSPC	No write space available
- * -ENODATA	Medium error
- * -EIO		unspecified I/O error
+ * Translate SCSI error code into block errors.
  */
-static int __scsi_error_from_host_byte(struct scsi_cmnd *cmd, int result)
+static blk_status_t __scsi_error_from_host_byte(struct scsi_cmnd *cmd,
+		int result)
 {
-	int error = 0;
-
-	switch(host_byte(result)) {
+	switch (host_byte(result)) {
 	case DID_TRANSPORT_FAILFAST:
-		error = -ENOLINK;
-		break;
+		return BLK_STS_TRANSPORT;
 	case DID_TARGET_FAILURE:
 		set_host_byte(cmd, DID_OK);
-		error = -EREMOTEIO;
-		break;
+		return BLK_STS_TARGET;
 	case DID_NEXUS_FAILURE:
-		set_host_byte(cmd, DID_OK);
-		error = -EBADE;
-		break;
+		return BLK_STS_NEXUS;
 	case DID_ALLOC_FAILURE:
 		set_host_byte(cmd, DID_OK);
-		error = -ENOSPC;
-		break;
+		return BLK_STS_NOSPC;
 	case DID_MEDIUM_ERROR:
 		set_host_byte(cmd, DID_OK);
-		error = -ENODATA;
-		break;
+		return BLK_STS_MEDIUM;
 	default:
-		error = -EIO;
-		break;
+		return BLK_STS_IOERR;
 	}
-
-	return error;
 }
 
 /*
@@ -769,7 +752,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	int result = cmd->result;
 	struct request_queue *q = cmd->device->request_queue;
 	struct request *req = cmd->request;
-	int error = 0;
+	blk_status_t error = BLK_STS_OK;
 	struct scsi_sense_hdr sshdr;
 	bool sense_valid = false;
 	int sense_deferred = 0, level = 0;
@@ -808,7 +791,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 			 * both sides at once.
 			 */
 			scsi_req(req->next_rq)->resid_len = scsi_in(cmd)->resid;
-			if (scsi_end_request(req, 0, blk_rq_bytes(req),
+			if (scsi_end_request(req, BLK_STS_OK, blk_rq_bytes(req),
 					blk_rq_bytes(req->next_rq)))
 				BUG();
 			return;
@@ -850,7 +833,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 			scsi_print_sense(cmd);
 		result = 0;
 		/* for passthrough error may be set */
-		error = 0;
+		error = BLK_STS_OK;
 	}
 
 	/*
@@ -922,18 +905,18 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 				action = ACTION_REPREP;
 			} else if (sshdr.asc == 0x10) /* DIX */ {
 				action = ACTION_FAIL;
-				error = -EILSEQ;
+				error = BLK_STS_PROTECTION;
 			/* INVALID COMMAND OPCODE or INVALID FIELD IN CDB */
 			} else if (sshdr.asc == 0x20 || sshdr.asc == 0x24) {
 				action = ACTION_FAIL;
-				error = -EREMOTEIO;
+				error = BLK_STS_TARGET;
 			} else
 				action = ACTION_FAIL;
 			break;
 		case ABORTED_COMMAND:
 			action = ACTION_FAIL;
 			if (sshdr.asc == 0x10) /* DIF */
-				error = -EILSEQ;
+				error = BLK_STS_PROTECTION;
 			break;
 		case NOT_READY:
 			/* If the device is in the process of becoming