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>

3 files changed, 28 insertions, 20 deletions

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 6fb3fd5efc11..b7cbd5d2cdea 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -2672,7 +2672,7 @@ static void __dasd_process_request_queue(struct dasd_block *block)
 	 */
 	if (basedev->state < DASD_STATE_READY) {
 		while ((req = blk_fetch_request(block->request_queue)))
-			__blk_end_request_all(req, -EIO);
+			__blk_end_request_all(req, BLK_STS_IOERR);
 		return;
 	}
 
@@ -2692,7 +2692,7 @@ static void __dasd_process_request_queue(struct dasd_block *block)
 				      "Rejecting write request %p",
 				      req);
 			blk_start_request(req);
-			__blk_end_request_all(req, -EIO);
+			__blk_end_request_all(req, BLK_STS_IOERR);
 			continue;
 		}
 		if (test_bit(DASD_FLAG_ABORTALL, &basedev->flags) &&
@@ -2702,7 +2702,7 @@ static void __dasd_process_request_queue(struct dasd_block *block)
 				      "Rejecting failfast request %p",
 				      req);
 			blk_start_request(req);
-			__blk_end_request_all(req, -ETIMEDOUT);
+			__blk_end_request_all(req, BLK_STS_TIMEOUT);
 			continue;
 		}
 		cqr = basedev->discipline->build_cp(basedev, block, req);
@@ -2734,7 +2734,7 @@ static void __dasd_process_request_queue(struct dasd_block *block)
 				      "on request %p",
 				      PTR_ERR(cqr), req);
 			blk_start_request(req);
-			__blk_end_request_all(req, -EIO);
+			__blk_end_request_all(req, BLK_STS_IOERR);
 			continue;
 		}
 		/*
@@ -2755,21 +2755,29 @@ static void __dasd_cleanup_cqr(struct dasd_ccw_req *cqr)
 {
 	struct request *req;
 	int status;
-	int error = 0;
+	blk_status_t error = BLK_STS_OK;
 
 	req = (struct request *) cqr->callback_data;
 	dasd_profile_end(cqr->block, cqr, req);
+
 	status = cqr->block->base->discipline->free_cp(cqr, req);
 	if (status < 0)
-		error = status;
+		error = errno_to_blk_status(status);
 	else if (status == 0) {
-		if (cqr->intrc == -EPERM)
-			error = -EBADE;
-		else if (cqr->intrc == -ENOLINK ||
-			 cqr->intrc == -ETIMEDOUT)
-			error = cqr->intrc;
-		else
-			error = -EIO;
+		switch (cqr->intrc) {
+		case -EPERM:
+			error = BLK_STS_NEXUS;
+			break;
+		case -ENOLINK:
+			error = BLK_STS_TRANSPORT;
+			break;
+		case -ETIMEDOUT:
+			error = BLK_STS_TIMEOUT;
+			break;
+		default:
+			error = BLK_STS_IOERR;
+			break;
+		}
 	}
 	__blk_end_request_all(req, error);
 }
@@ -3190,7 +3198,7 @@ static void dasd_flush_request_queue(struct dasd_block *block)
 
 	spin_lock_irq(&block->request_queue_lock);
 	while ((req = blk_fetch_request(block->request_queue)))
-		__blk_end_request_all(req, -EIO);
+		__blk_end_request_all(req, BLK_STS_IOERR);
 	spin_unlock_irq(&block->request_queue_lock);
 }
 
diff --git a/drivers/s390/block/scm_blk.c b/drivers/s390/block/scm_blk.c
index 152de6817875..3c2c84b72877 100644
--- a/drivers/s390/block/scm_blk.c
+++ b/drivers/s390/block/scm_blk.c
@@ -231,7 +231,7 @@ static inline void scm_request_init(struct scm_blk_dev *bdev,
 	aob->request.data = (u64) aobrq;
 	scmrq->bdev = bdev;
 	scmrq->retries = 4;
-	scmrq->error = 0;
+	scmrq->error = BLK_STS_OK;
 	/* We don't use all msbs - place aidaws at the end of the aob page. */
 	scmrq->next_aidaw = (void *) &aob->msb[nr_requests_per_io];
 	scm_request_cluster_init(scmrq);
@@ -364,7 +364,7 @@ static void __scmrq_log_error(struct scm_request *scmrq)
 {
 	struct aob *aob = scmrq->aob;
 
-	if (scmrq->error == -ETIMEDOUT)
+	if (scmrq->error == BLK_STS_TIMEOUT)
 		SCM_LOG(1, "Request timeout");
 	else {
 		SCM_LOG(1, "Request error");
@@ -377,7 +377,7 @@ static void __scmrq_log_error(struct scm_request *scmrq)
 		       scmrq->error);
 }
 
-void scm_blk_irq(struct scm_device *scmdev, void *data, int error)
+void scm_blk_irq(struct scm_device *scmdev, void *data, blk_status_t error)
 {
 	struct scm_request *scmrq = data;
 	struct scm_blk_dev *bdev = scmrq->bdev;
@@ -397,7 +397,7 @@ static void scm_blk_handle_error(struct scm_request *scmrq)
 	struct scm_blk_dev *bdev = scmrq->bdev;
 	unsigned long flags;
 
-	if (scmrq->error != -EIO)
+	if (scmrq->error != BLK_STS_IOERR)
 		goto restart;
 
 	/* For -EIO the response block is valid. */
diff --git a/drivers/s390/block/scm_blk.h b/drivers/s390/block/scm_blk.h
index 09218cdc5129..cd598d1a4eae 100644
--- a/drivers/s390/block/scm_blk.h
+++ b/drivers/s390/block/scm_blk.h
@@ -35,7 +35,7 @@ struct scm_request {
 	struct aob *aob;
 	struct list_head list;
 	u8 retries;
-	int error;
+	blk_status_t error;
 #ifdef CONFIG_SCM_BLOCK_CLUSTER_WRITE
 	struct {
 		enum {CLUSTER_NONE, CLUSTER_READ, CLUSTER_WRITE} state;
@@ -50,7 +50,7 @@ struct scm_request {
 int scm_blk_dev_setup(struct scm_blk_dev *, struct scm_device *);
 void scm_blk_dev_cleanup(struct scm_blk_dev *);
 void scm_blk_set_available(struct scm_blk_dev *);
-void scm_blk_irq(struct scm_device *, void *, int);
+void scm_blk_irq(struct scm_device *, void *, blk_status_t);
 
 void scm_request_finish(struct scm_request *);
 void scm_request_requeue(struct scm_request *);