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bio: add bvec_iter rewind API

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Some ->bi_end_io handlers (for example: pi_verify or decrypt handlers)
need to know original data vector, but after bio traverse io-stack it may
be advanced, splited and relocated many times so it is hard to guess
original iterator. Let's add 'bi_done' conter which accounts number
of bytes iterator was advanced during it's evolution. Later end_io handler
may easily restore original iterator by rewinding iterator to
iter->bi_done.

Note: this change makes sizeof (struct bvec_iter) multiple to 8

Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
[hch: switched to true/false return]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Dmitry Monakhov
2017-06-29 11:31:14 -07:00
committed by Jens Axboe
parent b1fb2c52b2
commit f9df1cd99e
2 changed files with 44 additions and 2 deletions
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19
include/linux/bio.h
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@@ -165,14 +165,29 @@ 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;
else {
iter->bi_done += bytes;
} 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) \
for (iter = (start); \
(iter).bi_size && \