block: remove bio_rewind_iter()

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 <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Suggested-by: Kent Overstreet <[email protected]>
Acked-by: Kent Overstreet <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Ming Lei <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Ming Lei 2018-09-05 15:45:54 -06:00 • committed by Jens Axboe
commit 7759eb23fd
4 changed files with 8 additions and 30 deletions

View file

@ -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;
@ -331,20 +333,14 @@ 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);
}