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, 10 insertions, 17 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)