linux-kernel - Re: [PATCH 15/21] iomap: Convert iomap_write_begin and iomap_write

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Date:   Wed, 3 Nov 2021 12:47:58 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     "Darrick J. Wong" <djwong@...nel.org>
Cc:     linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        Jens Axboe <axboe@...nel.dk>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 15/21] iomap: Convert iomap_write_begin and
 iomap_write_end to folios

On Wed, Nov 03, 2021 at 03:15:13AM +0000, Matthew Wilcox wrote:
> On Tue, Nov 02, 2021 at 04:22:15PM -0700, Darrick J. Wong wrote:
> > > +	page = folio_file_page(folio, pos >> PAGE_SHIFT);
> > 
> > Isn't this only needed in the BUFFER_HEAD case?
> 
> Good catch.  Want me to fold this in?
> 
> @@ -632,12 +631,12 @@ static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
>                 goto out_no_page;
>         }
>  
> -       page = folio_file_page(folio, pos >> PAGE_SHIFT);
>         if (srcmap->type == IOMAP_INLINE)
>                 status = iomap_write_begin_inline(iter, folio);
> -       else if (srcmap->flags & IOMAP_F_BUFFER_HEAD)
> +       else if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
> +               struct page *page = folio_file_page(folio, pos >> PAGE_SHIFT);
>                 status = __block_write_begin_int(page, pos, len, NULL, srcmap);

On second thoughts, this is silly.  __block_write_begin_int() doesn't
want the precise page (because it constructs buffer_heads and attaches
them to the passed-in page).  I should just pass &folio->page here.
And __block_write_begin_int() should be converted to take a folio
at some point.