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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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27
include/linux/bvec.h
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@@ -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 && \