Commit f9df1cd9 authored by Dmitry Monakhov's avatar Dmitry Monakhov Committed by Jens Axboe
Browse files

bio: add bvec_iter rewind API 



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: default avatarHannes Reinecke <hare@suse.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarDmitry Monakhov <dmonakhov@openvz.org>
[hch: switched to true/false return]
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b1fb2c52

include/linux/bio.h

+17 −2
Original line number Diff line number Diff line
@@ -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 &&						\

include/linux/bvec.h

+27 −0
Original line number Diff line number Diff line
@@ -40,6 +40,8 @@ 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 */

};
@@ -83,6 +85,7 @@ 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;
@@ -92,6 +95,30 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv, 
	return true;

}



static inline bool bvec_iter_rewind(const struct bio_vec *bv,

				     struct bvec_iter *iter,

				     unsigned int bytes)

{

	while (bytes) {

		unsigned len = min(bytes, iter->bi_bvec_done);



		if (iter->bi_bvec_done == 0) {

			if (WARN_ONCE(iter->bi_idx == 0,

				      "Attempted to rewind iter beyond "

				      "bvec's boundaries\n")) {

				return false;

			}

			iter->bi_idx--;

			iter->bi_bvec_done = __bvec_iter_bvec(bv, *iter)->bv_len;

			continue;

		}

		bytes -= len;

		iter->bi_size += len;

		iter->bi_bvec_done -= len;

	}

	return true;

}



#define for_each_bvec(bvl, bio_vec, iter, start)			\

	for (iter = (start);						\

	     (iter).bi_size &&						\

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