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dm io: use bvec iterator helpers to implement .get_page and .next_page 

Firstly we have mature bvec/bio iterator helper for iterate each
page in one bio, not necessary to reinvent a wheel to do that.

Secondly the coming multipage bvecs requires this patch.

Also add comments about the direct access to bvec table.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Ming Lei 2016-11-11 20:05:35 +08:00 committed by Mike Snitzer
parent 4f9c74c604
commit cacc7b0556
1 changed files with 24 additions and 10 deletions
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32
drivers/md/dm-io.c
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@ -162,7 +162,10 @@ struct dpages {
struct page **p, unsigned long *len, unsigned *offset);
void (*next_page)(struct dpages *dp);
union {
unsigned context_u;
struct bvec_iter context_bi;
};
void *context_ptr;
void *vma_invalidate_address;
@ -204,25 +207,36 @@ static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offse
static void bio_get_page(struct dpages *dp, struct page **p,
unsigned long *len, unsigned *offset)
{
struct bio_vec *bvec = dp->context_ptr;
*p = bvec->bv_page;
*len = bvec->bv_len - dp->context_u;
*offset = bvec->bv_offset + dp->context_u;
struct bio_vec bvec = bvec_iter_bvec((struct bio_vec *)dp->context_ptr,
dp->context_bi);
*p = bvec.bv_page;
*len = bvec.bv_len;
*offset = bvec.bv_offset;
/* avoid figuring it out again in bio_next_page() */
dp->context_bi.bi_sector = (sector_t)bvec.bv_len;
}
static void bio_next_page(struct dpages *dp)
{
struct bio_vec *bvec = dp->context_ptr;
dp->context_ptr = bvec + 1;
dp->context_u = 0;
unsigned int len = (unsigned int)dp->context_bi.bi_sector;
bvec_iter_advance((struct bio_vec *)dp->context_ptr,
&dp->context_bi, len);
}
static void bio_dp_init(struct dpages *dp, struct bio *bio)
{
dp->get_page = bio_get_page;
dp->next_page = bio_next_page;
dp->context_ptr = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
dp->context_u = bio->bi_iter.bi_bvec_done;
/*
* We just use bvec iterator to retrieve pages, so it is ok to
* access the bvec table directly here
*/
dp->context_ptr = bio->bi_io_vec;
dp->context_bi = bio->bi_iter;
}
/*