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block: remove bio_rewind_iter()

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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 5151842b9d (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.

Cc: Dmitry Monakhov <dmonakhov@openvz.org>
Cc: Hannes Reinecke <hare@suse.com>
Suggested-by: Kent Overstreet <kent.overstreet@gmail.com>
Acked-by: Kent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2018-09-05 15:45:54 -06:00 • committed by Jens Axboe
parent 3d0e63754f
commit 7759eb23fd
4 changed files with 8 additions and 30 deletions
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22
include/linux/bio.h
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@ -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;