block: add a bi_error field to struct bio

Currently we have two different ways to signal an I/O error on a BIO:

 (1) by clearing the BIO_UPTODATE flag
 (2) by returning a Linux errno value to the bi_end_io callback

The first one has the drawback of only communicating a single possible
error (-EIO), and the second one has the drawback of not beeing persistent
when bios are queued up, and are not passed along from child to parent
bio in the ever more popular chaining scenario.  Having both mechanisms
available has the additional drawback of utterly confusing driver authors
and introducing bugs where various I/O submitters only deal with one of
them, and the others have to add boilerplate code to deal with both kinds
of error returns.

So add a new bi_error field to store an errno value directly in struct
bio and remove the existing mechanisms to clean all this up.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

3 files changed, 13 insertions, 8 deletions

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 5e963a6d7c14..6b918177002d 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -195,8 +195,6 @@ static inline bool bvec_gap_to_prev(struct bio_vec *bprv, unsigned int offset)
 	return offset || ((bprv->bv_offset + bprv->bv_len) & (PAGE_SIZE - 1));
 }
 
-#define bio_io_error(bio) bio_endio((bio), -EIO)
-
 /*
  * drivers should _never_ use the all version - the bio may have been split
  * before it got to the driver and the driver won't own all of it
@@ -426,7 +424,14 @@ static inline struct bio *bio_clone_kmalloc(struct bio *bio, gfp_t gfp_mask)
 
 }
 
-extern void bio_endio(struct bio *, int);
+extern void bio_endio(struct bio *);
+
+static inline void bio_io_error(struct bio *bio)
+{
+	bio->bi_error = -EIO;
+	bio_endio(bio);
+}
+
 struct request_queue;
 extern int bio_phys_segments(struct request_queue *, struct bio *);
 
@@ -717,7 +722,7 @@ extern void bio_integrity_free(struct bio *);
 extern int bio_integrity_add_page(struct bio *, struct page *, unsigned int, unsigned int);
 extern bool bio_integrity_enabled(struct bio *bio);
 extern int bio_integrity_prep(struct bio *);
-extern void bio_integrity_endio(struct bio *, int);
+extern void bio_integrity_endio(struct bio *);
 extern void bio_integrity_advance(struct bio *, unsigned int);
 extern void bio_integrity_trim(struct bio *, unsigned int, unsigned int);
 extern int bio_integrity_clone(struct bio *, struct bio *, gfp_t);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 7303b3405520..6164fb8a817b 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -14,7 +14,7 @@ struct page;
 struct block_device;
 struct io_context;
 struct cgroup_subsys_state;
-typedef void (bio_end_io_t) (struct bio *, int);
+typedef void (bio_end_io_t) (struct bio *);
 typedef void (bio_destructor_t) (struct bio *);
 
 /*
@@ -53,6 +53,7 @@ struct bio {
 
 	struct bvec_iter	bi_iter;
 
+	int			bi_error;
 	/* Number of segments in this BIO after
 	 * physical address coalescing is performed.
 	 */
@@ -111,7 +112,6 @@ struct bio {
 /*
  * bio flags
  */
-#define BIO_UPTODATE	0	/* ok after I/O completion */
 #define BIO_SEG_VALID	1	/* bi_phys_segments valid */
 #define BIO_CLONED	2	/* doesn't own data */
 #define BIO_BOUNCED	3	/* bio is a bounce bio */
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 38874729dc5f..31496d201fdc 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -373,9 +373,9 @@ static inline void mem_cgroup_uncharge_swap(swp_entry_t entry)
 /* linux/mm/page_io.c */
 extern int swap_readpage(struct page *);
 extern int swap_writepage(struct page *page, struct writeback_control *wbc);
-extern void end_swap_bio_write(struct bio *bio, int err);
+extern void end_swap_bio_write(struct bio *bio);
 extern int __swap_writepage(struct page *page, struct writeback_control *wbc,
-	void (*end_write_func)(struct bio *, int));
+	bio_end_io_t end_write_func);
 extern int swap_set_page_dirty(struct page *page);
 
 int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,