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, 11 insertions, 9 deletions

diff --git a/drivers/scsi/osd/osd_initiator.c b/drivers/scsi/osd/osd_initiator.c
index 14785177ce7b..1e69a43b279d 100644
--- a/drivers/scsi/osd/osd_initiator.c
+++ b/drivers/scsi/osd/osd_initiator.c
@@ -446,7 +446,7 @@ static void _put_request(struct request *rq)
 	 *       code paths.
 	 */
 	if (unlikely(rq->bio))
-		blk_end_request(rq, -ENOMEM, blk_rq_bytes(rq));
+		blk_end_request(rq, BLK_STS_IOERR, blk_rq_bytes(rq));
 	else
 		blk_put_request(rq);
 }
@@ -474,7 +474,7 @@ void osd_end_request(struct osd_request *or)
 EXPORT_SYMBOL(osd_end_request);
 
 static void _set_error_resid(struct osd_request *or, struct request *req,
-			     int error)
+			     blk_status_t error)
 {
 	or->async_error = error;
 	or->req_errors = scsi_req(req)->result;
@@ -489,17 +489,19 @@ static void _set_error_resid(struct osd_request *or, struct request *req,
 
 int osd_execute_request(struct osd_request *or)
 {
-	int error;
-
 	blk_execute_rq(or->request->q, NULL, or->request, 0);
-	error = scsi_req(or->request)->result ? -EIO : 0;
 
-	_set_error_resid(or, or->request, error);
-	return error;
+	if (scsi_req(or->request)->result) {
+		_set_error_resid(or, or->request, BLK_STS_IOERR);
+		return -EIO;
+	}
+
+	_set_error_resid(or, or->request, BLK_STS_OK);
+	return 0;
 }
 EXPORT_SYMBOL(osd_execute_request);
 
-static void osd_request_async_done(struct request *req, int error)
+static void osd_request_async_done(struct request *req, blk_status_t error)
 {
 	struct osd_request *or = req->end_io_data;
 
@@ -1914,7 +1916,7 @@ analyze:
 		/* scsi sense is Empty, the request was never issued to target
 		 * linux return code might tell us what happened.
 		 */
-		if (or->async_error == -ENOMEM)
+		if (or->async_error == BLK_STS_RESOURCE)
 			osi->osd_err_pri = OSD_ERR_PRI_RESOURCE;
 		else
 			osi->osd_err_pri = OSD_ERR_PRI_UNREACHABLE;