linux-kernel - Re: [PATCH 5/7] block: Rework bio_for_each_folio

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Message-ID: <ZG/+88/G+hX5DyCX@dread.disaster.area>
Date:   Fri, 26 May 2023 10:36:03 +1000
From:   Dave Chinner <david@...morbit.com>
To:     Kent Overstreet <kent.overstreet@...ux.dev>
Cc:     linux-kernel@...r.kernel.org, axboe@...nel.dk,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH 5/7] block: Rework bio_for_each_folio_all()

On Thu, May 25, 2023 at 05:48:20PM -0400, Kent Overstreet wrote:
> This reimplements bio_for_each_folio_all() on top of the newly-reworked
> bvec_iter_all, and since it's now trivial we also provide
> bio_for_each_folio.
> 
> Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: linux-block@...r.kernel.org
> ---
>  fs/crypto/bio.c        |  9 +++--
>  fs/iomap/buffered-io.c | 14 ++++---
>  fs/verity/verify.c     |  9 +++--
>  include/linux/bio.h    | 91 +++++++++++++++++++++---------------------
>  include/linux/bvec.h   | 15 +++++--
>  5 files changed, 75 insertions(+), 63 deletions(-)
....
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index f86c7190c3..7ced281734 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -169,6 +169,42 @@ static inline void bio_advance(struct bio *bio, unsigned int nbytes)
>  #define bio_for_each_segment(bvl, bio, iter)				\
>  	__bio_for_each_segment(bvl, bio, iter, (bio)->bi_iter)
>  
> +struct folio_vec {
> +	struct folio	*fv_folio;
> +	size_t		fv_offset;
> +	size_t		fv_len;
> +};

Can we drop the "fv_" variable prefix here? It's just unnecessary
verbosity when we know we have a folio_vec structure. i.e fv->folio
is easier to read and type than fv->fv_folio...

Hmmm, this is probably not a good name considering "struct pagevec" is
something completely different - the equivalent is "struct
folio_batch" but I can see this being confusing for people who
largely expect some symmetry between page<->folio naming
conventions...

Also, why is this in bio.h and not in a mm/folio related header
file?

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com