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, 16 insertions, 0 deletions

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 61339bc44400..59378939a8cd 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -17,6 +17,22 @@ struct io_context;
 struct cgroup_subsys_state;
 typedef void (bio_end_io_t) (struct bio *);
 
+/*
+ * Block error status values.  See block/blk-core:blk_errors for the details.
+ */
+typedef u8 __bitwise blk_status_t;
+#define	BLK_STS_OK 0
+#define BLK_STS_NOTSUPP		((__force blk_status_t)1)
+#define BLK_STS_TIMEOUT		((__force blk_status_t)2)
+#define BLK_STS_NOSPC		((__force blk_status_t)3)
+#define BLK_STS_TRANSPORT	((__force blk_status_t)4)
+#define BLK_STS_TARGET		((__force blk_status_t)5)
+#define BLK_STS_NEXUS		((__force blk_status_t)6)
+#define BLK_STS_MEDIUM		((__force blk_status_t)7)
+#define BLK_STS_PROTECTION	((__force blk_status_t)8)
+#define BLK_STS_RESOURCE	((__force blk_status_t)9)
+#define BLK_STS_IOERR		((__force blk_status_t)10)
+
 struct blk_issue_stat {
 	u64 stat;
 };