It is pointed that bio_rewind_iter() is one very bad API[1]: 1) bio size may not be restored after rewinding
2) it causes some bogus change, such as 5151842b9d8732 (block: reset bi_iter.bi_done after splitting bio) 3) rewinding really makes things complicated wrt. bio splitting 4) unnecessary updating of .bi_done in fast path [1] https://marc.info/?t=153549924200005&r=1&w=2 So this patch takes Kent's suggestion to restore one bio into its original state via saving bio iterator(struct bvec_iter) in bio_integrity_prep(), given now bio_rewind_iter() is only used by bio integrity code. Suggested-by: Kent Overstreet <[email protected]> Cc: Kent Overstreet <[email protected]> Cc: Dmitry Monakhov <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Hannes Reinecke <[email protected]> Signed-off-by: Ming Lei <[email protected]> --- block/bio-integrity.c | 10 +++------- block/bio.c | 1 - include/linux/bio.h | 22 ++++------------------ include/linux/bvec.h | 3 --- 4 files changed, 7 insertions(+), 29 deletions(-) diff --git a/block/bio-integrity.c b/block/bio-integrity.c index 67b5fb861a51..839c332069a9 100644 --- a/block/bio-integrity.c +++ b/block/bio-integrity.c @@ -306,6 +306,8 @@ bool bio_integrity_prep(struct bio *bio) if (bio_data_dir(bio) == WRITE) { bio_integrity_process(bio, &bio->bi_iter, bi->profile->generate_fn); + } else { + bip->bio_iter = bio->bi_iter; } return true; @@ -331,19 +333,13 @@ static void bio_integrity_verify_fn(struct work_struct *work) container_of(work, struct bio_integrity_payload, bip_work); struct bio *bio = bip->bip_bio; struct blk_integrity *bi = blk_get_integrity(bio->bi_disk); - struct bvec_iter iter = bio->bi_iter; /* * At the moment verify is called bio's iterator was advanced * during split and completion, we need to rewind iterator to * it's original position. */ - if (bio_rewind_iter(bio, &iter, iter.bi_done)) { - bio->bi_status = bio_integrity_process(bio, &iter, - bi->profile->verify_fn); - } else { - bio->bi_status = BLK_STS_IOERR; - } + bio->bi_status = bio_integrity_process(bio, &bip->bio_iter, bi->profile->verify_fn); bio_integrity_free(bio); bio_endio(bio); diff --git a/block/bio.c b/block/bio.c index b12966e415d3..cc57cbbebbfd 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1807,7 +1807,6 @@ struct bio *bio_split(struct bio *bio, int sectors, bio_integrity_trim(split); bio_advance(bio, split->bi_iter.bi_size); - bio->bi_iter.bi_done = 0; if (bio_flagged(bio, BIO_TRACE_COMPLETION)) bio_set_flag(split, BIO_TRACE_COMPLETION); diff --git a/include/linux/bio.h b/include/linux/bio.h index 51371740d2a8..14b4fa266357 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -170,27 +170,11 @@ static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter, { iter->bi_sector += bytes >> 9; - if (bio_no_advance_iter(bio)) { + if (bio_no_advance_iter(bio)) iter->bi_size -= bytes; - iter->bi_done += bytes; - } else { + else bvec_iter_advance(bio->bi_io_vec, iter, bytes); /* TODO: It is reasonable to complete bio with error here. */ - } -} - -static inline bool bio_rewind_iter(struct bio *bio, struct bvec_iter *iter, - unsigned int bytes) -{ - iter->bi_sector -= bytes >> 9; - - if (bio_no_advance_iter(bio)) { - iter->bi_size += bytes; - iter->bi_done -= bytes; - return true; - } - - return bvec_iter_rewind(bio->bi_io_vec, iter, bytes); } #define __bio_for_each_segment(bvl, bio, iter, start) \ @@ -353,6 +337,8 @@ struct bio_integrity_payload { unsigned short bip_max_vcnt; /* integrity bio_vec slots */ unsigned short bip_flags; /* control flags */ + struct bvec_iter bio_iter; /* for rewinding parent bio */ + struct work_struct bip_work; /* I/O completion */ struct bio_vec *bip_vec; diff --git a/include/linux/bvec.h b/include/linux/bvec.h index fe7a22dd133b..02c73c6aa805 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -40,8 +40,6 @@ struct bvec_iter { unsigned int bi_idx; /* current index into bvl_vec */ - unsigned int bi_done; /* number of bytes completed */ - unsigned int bi_bvec_done; /* number of bytes completed in current bvec */ }; @@ -85,7 +83,6 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv, bytes -= len; iter->bi_size -= len; iter->bi_bvec_done += len; - iter->bi_done += len; if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) { iter->bi_bvec_done = 0; -- 2.9.5
