Re: [PATCH V10 15/19] block: always define BIO_MAX_PAGES as 256

Omar Sandoval
2018-11-16T01:59:41Z

On Thu, Nov 15, 2018 at 04:53:02PM +0800, Ming Lei wrote:
> Now multi-page bvec can cover CONFIG_THP_SWAP, so we don't need to
> increase BIO_MAX_PAGES for it.

You mentioned to it in the cover letter, but this needs more explanation
in the commit message. Why did CONFIG_THP_SWAP require > 256? Why does
multipage bvecs remove that requirement?

> Cc: Dave Chinner <dchinner@redhat.com>
> Cc: Kent Overstreet <kent.overstreet@gmail.com>
> Cc: Mike Snitzer <snitzer@redhat.com>
> Cc: dm-devel@redhat.com
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Cc: linux-fsdevel@vger.kernel.org
> Cc: Shaohua Li <shli@kernel.org>
> Cc: linux-raid@vger.kernel.org
> Cc: linux-erofs@lists.ozlabs.org
> Cc: David Sterba <dsterba@suse.com>
> Cc: linux-btrfs@vger.kernel.org
> Cc: Darrick J. Wong <darrick.wong@oracle.com>
> Cc: linux-xfs@vger.kernel.org
> Cc: Gao Xiang <gaoxiang25@huawei.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Theodore Ts'o <tytso@mit.edu>
> Cc: linux-ext4@vger.kernel.org
> Cc: Coly Li <colyli@suse.de>
> Cc: linux-bcache@vger.kernel.org
> Cc: Boaz Harrosh <ooo@electrozaur.com>
> Cc: Bob Peterson <rpeterso@redhat.com>
> Cc: cluster-devel@redhat.com
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> include/linux/bio.h | 8 --------
> 1 file changed, 8 deletions(-)
>
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 5040e9a2eb09..277921ad42e7 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -34,15 +34,7 @@
> #define BIO_BUG_ON
> #endif
>
> -#ifdef CONFIG_THP_SWAP
> -#if HPAGE_PMD_NR > 256
> -#define BIO_MAX_PAGES HPAGE_PMD_NR
> -#else
> #define BIO_MAX_PAGES 256
> -#endif
> -#else
> -#define BIO_MAX_PAGES 256
> -#endif
>
> #define bio_prio(bio) (bio)->bi_ioprio
> #define bio_set_prio(bio, prio) ((bio)->bi_ioprio = prio)
> --
> 2.9.5
>