On 2016/12/27 下午11:55, Ming Lei wrote:
> This patch adds comment on usage of bio_alloc_pages(),
> also comments on one special case of bch_data_verify().
>
> Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
> ---
> block/bio.c | 4 +++-
> drivers/md/bcache/debug.c | 6 ++++++
> 2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 2b375020fc49..d4a1e0b63ea0 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -961,7 +961,9 @@ EXPORT_SYMBOL(bio_advance);
> * @bio: bio to allocate pages for
> * @gfp_mask: flags for allocation
> *
> - * Allocates pages up to @bio->bi_vcnt.
> + * Allocates pages up to @bio->bi_vcnt, and this function should only
> + * be called on a new initialized bio, which means all pages aren't added
> + * to the bio via bio_add_page() yet.
> *
> * Returns 0 on success, -ENOMEM on failure. On failure, any allocated pages are
> * freed.
> diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c
> index 06f55056aaae..48d03e8b3385 100644
> --- a/drivers/md/bcache/debug.c
> +++ b/drivers/md/bcache/debug.c
> @@ -110,6 +110,12 @@ void bch_data_verify(struct cached_dev *dc, struct bio *bio)
> struct bio_vec bv, cbv;
> struct bvec_iter iter, citer = { 0 };
>
> + /*
> + * Once multipage bvec is supported, the bio_clone()
> + * has to make sure page count in this bio can be held
> + * in the new cloned bio because each single page need
> + * to assign to each bvec of the new bio.
> + */
> check = bio_clone(bio, GFP_NOIO);
> if (!check)
> return;
>
Acked-by: Coly Li <colyli@xxxxxxx>
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