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, 14 insertions, 17 deletions

diff --git a/drivers/block/skd_main.c b/drivers/block/skd_main.c
index 27833e4dae2a..e6c526861703 100644
--- a/drivers/block/skd_main.c
+++ b/drivers/block/skd_main.c
@@ -451,8 +451,8 @@ static void skd_send_special_fitmsg(struct skd_device *skdev,
 				    struct skd_special_context *skspcl);
 static void skd_request_fn(struct request_queue *rq);
 static void skd_end_request(struct skd_device *skdev,
-			    struct skd_request_context *skreq, int error);
-static int skd_preop_sg_list(struct skd_device *skdev,
+		struct skd_request_context *skreq, blk_status_t status);
+static bool skd_preop_sg_list(struct skd_device *skdev,
 			     struct skd_request_context *skreq);
 static void skd_postop_sg_list(struct skd_device *skdev,
 			       struct skd_request_context *skreq);
@@ -491,7 +491,7 @@ static void skd_fail_all_pending(struct skd_device *skdev)
 		if (req == NULL)
 			break;
 		blk_start_request(req);
-		__blk_end_request_all(req, -EIO);
+		__blk_end_request_all(req, BLK_STS_IOERR);
 	}
 }
 
@@ -545,7 +545,6 @@ static void skd_request_fn(struct request_queue *q)
 	struct request *req = NULL;
 	struct skd_scsi_request *scsi_req;
 	unsigned long io_flags;
-	int error;
 	u32 lba;
 	u32 count;
 	int data_dir;
@@ -716,9 +715,7 @@ static void skd_request_fn(struct request_queue *q)
 		if (!req->bio)
 			goto skip_sg;
 
-		error = skd_preop_sg_list(skdev, skreq);
-
-		if (error != 0) {
+		if (!skd_preop_sg_list(skdev, skreq)) {
 			/*
 			 * Complete the native request with error.
 			 * Note that the request context is still at the
@@ -730,7 +727,7 @@ static void skd_request_fn(struct request_queue *q)
 			 */
 			pr_debug("%s:%s:%d error Out\n",
 				 skdev->name, __func__, __LINE__);
-			skd_end_request(skdev, skreq, error);
+			skd_end_request(skdev, skreq, BLK_STS_RESOURCE);
 			continue;
 		}
 
@@ -805,7 +802,7 @@ skip_sg:
 }
 
 static void skd_end_request(struct skd_device *skdev,
-			    struct skd_request_context *skreq, int error)
+		struct skd_request_context *skreq, blk_status_t error)
 {
 	if (unlikely(error)) {
 		struct request *req = skreq->req;
@@ -822,7 +819,7 @@ static void skd_end_request(struct skd_device *skdev,
 	__blk_end_request_all(skreq->req, error);
 }
 
-static int skd_preop_sg_list(struct skd_device *skdev,
+static bool skd_preop_sg_list(struct skd_device *skdev,
 			     struct skd_request_context *skreq)
 {
 	struct request *req = skreq->req;
@@ -839,7 +836,7 @@ static int skd_preop_sg_list(struct skd_device *skdev,
 
 	n_sg = blk_rq_map_sg(skdev->queue, req, sg);
 	if (n_sg <= 0)
-		return -EINVAL;
+		return false;
 
 	/*
 	 * Map scatterlist to PCI bus addresses.
@@ -847,7 +844,7 @@ static int skd_preop_sg_list(struct skd_device *skdev,
 	 */
 	n_sg = pci_map_sg(skdev->pdev, sg, n_sg, pci_dir);
 	if (n_sg <= 0)
-		return -EINVAL;
+		return false;
 
 	SKD_ASSERT(n_sg <= skdev->sgs_per_request);
 
@@ -882,7 +879,7 @@ static int skd_preop_sg_list(struct skd_device *skdev,
 		}
 	}
 
-	return 0;
+	return true;
 }
 
 static void skd_postop_sg_list(struct skd_device *skdev,
@@ -2333,7 +2330,7 @@ static void skd_resolve_req_exception(struct skd_device *skdev,
 	switch (skd_check_status(skdev, cmp_status, &skreq->err_info)) {
 	case SKD_CHECK_STATUS_REPORT_GOOD:
 	case SKD_CHECK_STATUS_REPORT_SMART_ALERT:
-		skd_end_request(skdev, skreq, 0);
+		skd_end_request(skdev, skreq, BLK_STS_OK);
 		break;
 
 	case SKD_CHECK_STATUS_BUSY_IMMINENT:
@@ -2355,7 +2352,7 @@ static void skd_resolve_req_exception(struct skd_device *skdev,
 
 	case SKD_CHECK_STATUS_REPORT_ERROR:
 	default:
-		skd_end_request(skdev, skreq, -EIO);
+		skd_end_request(skdev, skreq, BLK_STS_IOERR);
 		break;
 	}
 }
@@ -2748,7 +2745,7 @@ static int skd_isr_completion_posted(struct skd_device *skdev,
 			 * native request.
 			 */
 			if (likely(cmp_status == SAM_STAT_GOOD))
-				skd_end_request(skdev, skreq, 0);
+				skd_end_request(skdev, skreq, BLK_STS_OK);
 			else
 				skd_resolve_req_exception(skdev, skreq);
 		}
@@ -3190,7 +3187,7 @@ static void skd_recover_requests(struct skd_device *skdev, int requeue)
 			    SKD_MAX_RETRIES)
 				blk_requeue_request(skdev->queue, skreq->req);
 			else
-				skd_end_request(skdev, skreq, -EIO);
+				skd_end_request(skdev, skreq, BLK_STS_IOERR);
 
 			skreq->req = NULL;