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, 12 insertions, 9 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 019f18c65098..2a8871638453 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -55,7 +55,7 @@ struct blk_stat_callback;
  */
 #define BLKCG_MAX_POLS          3
 
-typedef void (rq_end_io_fn)(struct request *, int);
+typedef void (rq_end_io_fn)(struct request *, blk_status_t);
 
 #define BLK_RL_SYNCFULL         (1U << 0)
 #define BLK_RL_ASYNCFULL        (1U << 1)
@@ -940,7 +940,7 @@ extern int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
                              int (*bio_ctr)(struct bio *, struct bio *, void *),
                              void *data);
 extern void blk_rq_unprep_clone(struct request *rq);
-extern int blk_insert_cloned_request(struct request_queue *q,
+extern blk_status_t blk_insert_cloned_request(struct request_queue *q,
                                      struct request *rq);
 extern int blk_rq_append_bio(struct request *rq, struct bio *bio);
 extern void blk_delay_queue(struct request_queue *, unsigned long);
@@ -980,6 +980,9 @@ extern void blk_execute_rq(struct request_queue *, struct gendisk *,
 extern void blk_execute_rq_nowait(struct request_queue *, struct gendisk *,
                                   struct request *, int, rq_end_io_fn *);
 
+int blk_status_to_errno(blk_status_t status);
+blk_status_t errno_to_blk_status(int errno);
+
 bool blk_mq_poll(struct request_queue *q, blk_qc_t cookie);
 
 static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
@@ -1112,16 +1115,16 @@ extern struct request *blk_fetch_request(struct request_queue *q);
  * blk_end_request() for parts of the original function.
  * This prevents code duplication in drivers.
  */
-extern bool blk_update_request(struct request *rq, int error,
+extern bool blk_update_request(struct request *rq, blk_status_t error,
                                unsigned int nr_bytes);
-extern void blk_finish_request(struct request *rq, int error);
-extern bool blk_end_request(struct request *rq, int error,
+extern void blk_finish_request(struct request *rq, blk_status_t error);
+extern bool blk_end_request(struct request *rq, blk_status_t error,
                             unsigned int nr_bytes);
-extern void blk_end_request_all(struct request *rq, int error);
-extern bool __blk_end_request(struct request *rq, int error,
+extern void blk_end_request_all(struct request *rq, blk_status_t error);
+extern bool __blk_end_request(struct request *rq, blk_status_t error,
                               unsigned int nr_bytes);
-extern void __blk_end_request_all(struct request *rq, int error);
-extern bool __blk_end_request_cur(struct request *rq, int error);
+extern void __blk_end_request_all(struct request *rq, blk_status_t error);
+extern bool __blk_end_request_cur(struct request *rq, blk_status_t error);
 
 extern void blk_complete_request(struct request *);
 extern void __blk_complete_request(struct request *);