Re: [Cluster-devel] [PATCH V12 14/20] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages()

[Omar Sandoval]

On Mon, Nov 26, 2018 at 10:17:14AM +0800, 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.
> 
> Acked-by: Coly Li 
> Reviewed-by: Christoph Hellwig 

Reviewed-by: Omar Sandoval 

> Signed-off-by: Ming Lei 
> ---
>  drivers/md/bcache/util.c | 6 +-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
> index 20eddeac1531..62fb917f7a4f 100644
> --- a/drivers/md/bcache/util.c
> +++ b/drivers/md/bcache/util.c
> @@ -270,7 +270,11 @@ int bch_bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
>   int i;
>   struct bio_vec *bv;
>  
> - bio_for_each_segment_all(bv, bio, i) {
> + /*
> +  * This is called on freshly new bio, so it is safe to access the
> +  * bvec table directly.
> +  */
> + for (i = 0, bv = bio->bi_io_vec; i < bio->bi_vcnt; bv++, i++) {
>   bv->bv_page = alloc_page(gfp_mask);
>   if (!bv->bv_page) {
>   while (--bv >= bio->bi_io_vec)
> -- 
> 2.9.5
> 

[Cluster-devel] [PATCH V12 14/20] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages()

[Ming Lei]

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.

Acked-by: Coly Li 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Ming Lei 
---
 drivers/md/bcache/util.c | 6 +-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
index 20eddeac1531..62fb917f7a4f 100644
--- a/drivers/md/bcache/util.c
+++ b/drivers/md/bcache/util.c
@@ -270,7 +270,11 @@ int bch_bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
int i;
struct bio_vec *bv;
 
-   bio_for_each_segment_all(bv, bio, i) {
+   /*
+* This is called on freshly new bio, so it is safe to access the
+* bvec table directly.
+*/
+   for (i = 0, bv = bio->bi_io_vec; i < bio->bi_vcnt; bv++, i++) {
bv->bv_page = alloc_page(gfp_mask);
if (!bv->bv_page) {
while (--bv >= bio->bi_io_vec)
-- 
2.9.5