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, 21 insertions, 28 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index ceeeb495d01c..39262e344ae1 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -1449,22 +1449,15 @@ static void activate_path_work(struct work_struct *work)
 	activate_or_offline_path(pgpath);
 }
 
-static int noretry_error(int error)
+static int noretry_error(blk_status_t error)
 {
 	switch (error) {
-	case -EBADE:
-		/*
-		 * EBADE signals an reservation conflict.
-		 * We shouldn't fail the path here as we can communicate with
-		 * the target.  We should failover to the next path, but in
-		 * doing so we might be causing a ping-pong between paths.
-		 * So just return the reservation conflict error.
-		 */
-	case -EOPNOTSUPP:
-	case -EREMOTEIO:
-	case -EILSEQ:
-	case -ENODATA:
-	case -ENOSPC:
+	case BLK_STS_NOTSUPP:
+	case BLK_STS_NOSPC:
+	case BLK_STS_TARGET:
+	case BLK_STS_NEXUS:
+	case BLK_STS_MEDIUM:
+	case BLK_STS_RESOURCE:
 		return 1;
 	}
 
@@ -1473,7 +1466,7 @@ static int noretry_error(int error)
 }
 
 static int multipath_end_io(struct dm_target *ti, struct request *clone,
-			    int error, union map_info *map_context)
+			    blk_status_t error, union map_info *map_context)
 {
 	struct dm_mpath_io *mpio = get_mpio(map_context);
 	struct pgpath *pgpath = mpio->pgpath;
@@ -1500,7 +1493,7 @@ static int multipath_end_io(struct dm_target *ti, struct request *clone,
 
 		if (atomic_read(&m->nr_valid_paths) == 0 &&
 		    !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
-			if (error == -EIO)
+			if (error == BLK_STS_IOERR)
 				dm_report_EIO(m);
 			/* complete with the original error */
 			r = DM_ENDIO_DONE;
@@ -1525,7 +1518,7 @@ static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone, int *er
 	unsigned long flags;
 	int r = DM_ENDIO_DONE;
 
-	if (!*error || noretry_error(*error))
+	if (!*error || noretry_error(errno_to_blk_status(*error)))
 		goto done;
 
 	if (pgpath)
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index b639fa7246ee..bee334389173 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -119,7 +119,7 @@ static void end_clone_bio(struct bio *clone)
 	struct dm_rq_target_io *tio = info->tio;
 	struct bio *bio = info->orig;
 	unsigned int nr_bytes = info->orig->bi_iter.bi_size;
-	int error = clone->bi_error;
+	blk_status_t error = errno_to_blk_status(clone->bi_error);
 
 	bio_put(clone);
 
@@ -158,7 +158,7 @@ static void end_clone_bio(struct bio *clone)
 	 * Do not use blk_end_request() here, because it may complete
 	 * the original request before the clone, and break the ordering.
 	 */
-	blk_update_request(tio->orig, 0, nr_bytes);
+	blk_update_request(tio->orig, BLK_STS_OK, nr_bytes);
 }
 
 static struct dm_rq_target_io *tio_from_request(struct request *rq)
@@ -216,7 +216,7 @@ static void rq_completed(struct mapped_device *md, int rw, bool run_queue)
  * Must be called without clone's queue lock held,
  * see end_clone_request() for more details.
  */
-static void dm_end_request(struct request *clone, int error)
+static void dm_end_request(struct request *clone, blk_status_t error)
 {
 	int rw = rq_data_dir(clone);
 	struct dm_rq_target_io *tio = clone->end_io_data;
@@ -285,7 +285,7 @@ static void dm_requeue_original_request(struct dm_rq_target_io *tio, bool delay_
 	rq_completed(md, rw, false);
 }
 
-static void dm_done(struct request *clone, int error, bool mapped)
+static void dm_done(struct request *clone, blk_status_t error, bool mapped)
 {
 	int r = DM_ENDIO_DONE;
 	struct dm_rq_target_io *tio = clone->end_io_data;
@@ -298,7 +298,7 @@ static void dm_done(struct request *clone, int error, bool mapped)
 			r = rq_end_io(tio->ti, clone, error, &tio->info);
 	}
 
-	if (unlikely(error == -EREMOTEIO)) {
+	if (unlikely(error == BLK_STS_TARGET)) {
 		if (req_op(clone) == REQ_OP_WRITE_SAME &&
 		    !clone->q->limits.max_write_same_sectors)
 			disable_write_same(tio->md);
@@ -358,7 +358,7 @@ static void dm_softirq_done(struct request *rq)
  * Complete the clone and the original request with the error status
  * through softirq context.
  */
-static void dm_complete_request(struct request *rq, int error)
+static void dm_complete_request(struct request *rq, blk_status_t error)
 {
 	struct dm_rq_target_io *tio = tio_from_request(rq);
 
@@ -375,7 +375,7 @@ static void dm_complete_request(struct request *rq, int error)
  * Target's rq_end_io() function isn't called.
  * This may be used when the target's map_rq() or clone_and_map_rq() functions fail.
  */
-static void dm_kill_unmapped_request(struct request *rq, int error)
+static void dm_kill_unmapped_request(struct request *rq, blk_status_t error)
 {
 	rq->rq_flags |= RQF_FAILED;
 	dm_complete_request(rq, error);
@@ -384,7 +384,7 @@ static void dm_kill_unmapped_request(struct request *rq, int error)
 /*
  * Called with the clone's queue lock held (in the case of .request_fn)
  */
-static void end_clone_request(struct request *clone, int error)
+static void end_clone_request(struct request *clone, blk_status_t error)
 {
 	struct dm_rq_target_io *tio = clone->end_io_data;
 
@@ -401,7 +401,7 @@ static void end_clone_request(struct request *clone, int error)
 
 static void dm_dispatch_clone_request(struct request *clone, struct request *rq)
 {
-	int r;
+	blk_status_t r;
 
 	if (blk_queue_io_stat(clone->q))
 		clone->rq_flags |= RQF_IO_STAT;
@@ -506,7 +506,7 @@ static int map_request(struct dm_rq_target_io *tio)
 		break;
 	case DM_MAPIO_KILL:
 		/* The target wants to complete the I/O */
-		dm_kill_unmapped_request(rq, -EIO);
+		dm_kill_unmapped_request(rq, BLK_STS_IOERR);
 		break;
 	default:
 		DMWARN("unimplemented target map return value: %d", r);
diff --git a/drivers/md/dm-rq.h b/drivers/md/dm-rq.h
index f0020d21b95f..9813922e4fe5 100644
--- a/drivers/md/dm-rq.h
+++ b/drivers/md/dm-rq.h
@@ -24,7 +24,7 @@ struct dm_rq_target_io {
 	struct dm_target *ti;
 	struct request *orig, *clone;
 	struct kthread_work work;
-	int error;
+	blk_status_t error;
 	union map_info info;
 	struct dm_stats_aux stats_aux;
 	unsigned long duration_jiffies;