linux-kernel - Re: [PATCH v2 2/7] btrfs: Convert __process_pages_contig() to use filemap_get_folios

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Date:   Mon, 22 Aug 2022 11:32:45 -0700
From:   Vishal Moola <vishal.moola@...il.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-btrfs@...r.kernel.org, linux-nilfs@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/7] btrfs: Convert __process_pages_contig() to use filemap_get_folios_contig()

On Tue, Aug 16, 2022 at 10:53 AM Vishal Moola (Oracle)
<vishal.moola@...il.com> wrote:
>
> Convert to use folios throughout. This is in preparation for the removal of
> find_get_pages_contig(). Now also supports large folios.
>
> Since we may receive more than nr_pages pages, nr_pages may underflow.
> Since nr_pages > 0 is equivalent to index <= end_index, we replaced it
> with this check instead.
>
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>
> ---
>  fs/btrfs/extent_io.c | 33 +++++++++++++++------------------
>  1 file changed, 15 insertions(+), 18 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 8f6b544ae616..f16929bc531b 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -1882,9 +1882,8 @@ static int __process_pages_contig(struct address_space *mapping,
>         pgoff_t start_index = start >> PAGE_SHIFT;
>         pgoff_t end_index = end >> PAGE_SHIFT;
>         pgoff_t index = start_index;
> -       unsigned long nr_pages = end_index - start_index + 1;
>         unsigned long pages_processed = 0;
> -       struct page *pages[16];
> +       struct folio_batch fbatch;
>         int err = 0;
>         int i;
>
> @@ -1893,16 +1892,17 @@ static int __process_pages_contig(struct address_space *mapping,
>                 ASSERT(processed_end && *processed_end == start);
>         }
>
> -       if ((page_ops & PAGE_SET_ERROR) && nr_pages > 0)
> +       if ((page_ops & PAGE_SET_ERROR) && start_index <= end_index)
>                 mapping_set_error(mapping, -EIO);
>
> -       while (nr_pages > 0) {
> -               int found_pages;
> +       folio_batch_init(&fbatch);
> +       while (index <= end_index) {
> +               int found_folios;
> +
> +               found_folios = filemap_get_folios_contig(mapping, &index,
> +                               end_index, &fbatch);
>
> -               found_pages = find_get_pages_contig(mapping, index,
> -                                    min_t(unsigned long,
> -                                    nr_pages, ARRAY_SIZE(pages)), pages);
> -               if (found_pages == 0) {
> +               if (found_folios == 0) {
>                         /*
>                          * Only if we're going to lock these pages, we can find
>                          * nothing at @index.
> @@ -1912,23 +1912,20 @@ static int __process_pages_contig(struct address_space *mapping,
>                         goto out;
>                 }
>
> -               for (i = 0; i < found_pages; i++) {
> +               for (i = 0; i < found_folios; i++) {
>                         int process_ret;
> -
> +                       struct folio *folio = fbatch.folios[i];
>                         process_ret = process_one_page(fs_info, mapping,
> -                                       pages[i], locked_page, page_ops,
> +                                       &folio->page, locked_page, page_ops,
>                                         start, end);
>                         if (process_ret < 0) {
> -                               for (; i < found_pages; i++)
> -                                       put_page(pages[i]);
>                                 err = -EAGAIN;
> +                               folio_batch_release(&fbatch);
>                                 goto out;
>                         }
> -                       put_page(pages[i]);
> -                       pages_processed++;
> +                       pages_processed += folio_nr_pages(folio);
>                 }
> -               nr_pages -= found_pages;
> -               index += found_pages;
> +               folio_batch_release(&fbatch);
>                 cond_resched();
>         }
>  out:
> --
> 2.36.1
>
Just following up on these btrfs patches (2/7, 3/7, 4/7). Does anyone have
time to review them this week? Feedback would be appreciated.