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SubjectRe: [PATCH V7 20/24] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages()
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On 2018/6/27 8:45 PM, Ming Lei wrote:
> bch_bio_alloc_pages() is always called on one new bio, so it is safe
> to access the bvec table directly. Given it is the only kind of this
> case, open code the bvec table access since bio_for_each_segment_all()
> will be changed to support for iterating over multipage bvec.
>
> Cc: Coly Li <colyli@suse.de>
> Cc: linux-bcache@vger.kernel.org
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> drivers/md/bcache/util.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
> index fc479b026d6d..9f2a6fd5dfc9 100644
> --- a/drivers/md/bcache/util.c
> +++ b/drivers/md/bcache/util.c
> @@ -268,7 +268,7 @@ int bch_bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
> int i;
> struct bio_vec *bv;
>

Hi Ming,

> - bio_for_each_segment_all(bv, bio, i) {
> + for (i = 0, bv = bio->bi_io_vec; i < bio->bi_vcnt; bv++) {


Is it possible to treat this as a special condition of
bio_for_each_segement_all() ? I mean only iterate one time in
bvec_for_each_segment(). I hope the above change is not our last choice
before I reply an Acked-by :-)

Thanks.

Coly Li

> bv->bv_page = alloc_page(gfp_mask);
> if (!bv->bv_page) {
> while (--bv >= bio->bi_io_vec)
>

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