Re: [PATCH v5 10/23] ext4: Convert mpage_prepare_extent_to_map() to use filemap_get_folios_tag()

[Vishal Moola <vishal.moola@gmail.com>]

On Wed, Jan 4, 2023 at 1:15 PM Vishal Moola (Oracle)
<vishal.moola@gmail.com> wrote:
>
> Converted the function to use folios throughout. This is in preparation
> for the removal of find_get_pages_range_tag(). Now supports large
> folios. This change removes 11 calls to compound_head().
>
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
> ---
>  fs/ext4/inode.c | 65 ++++++++++++++++++++++++-------------------------
>  1 file changed, 32 insertions(+), 33 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 9d9f414f99fe..fb6cd994e59a 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2595,8 +2595,8 @@ static bool ext4_page_nomap_can_writeout(struct page *page)
>  static int mpage_prepare_extent_to_map(struct mpage_da_data *mpd)
>  {
>         struct address_space *mapping = mpd->inode->i_mapping;
> -       struct pagevec pvec;
> -       unsigned int nr_pages;
> +       struct folio_batch fbatch;
> +       unsigned int nr_folios;
>         long left = mpd->wbc->nr_to_write;
>         pgoff_t index = mpd->first_page;
>         pgoff_t end = mpd->last_page;
> @@ -2610,18 +2610,17 @@ static int mpage_prepare_extent_to_map(struct mpage_da_data *mpd)
>                 tag = PAGECACHE_TAG_TOWRITE;
>         else
>                 tag = PAGECACHE_TAG_DIRTY;
> -
> -       pagevec_init(&pvec);
> +       folio_batch_init(&fbatch);
>         mpd->map.m_len = 0;
>         mpd->next_page = index;
>         while (index <= end) {
> -               nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, end,
> -                               tag);
> -               if (nr_pages == 0)
> +               nr_folios = filemap_get_folios_tag(mapping, &index, end,
> +                               tag, &fbatch);
> +               if (nr_folios == 0)
>                         break;
>
> -               for (i = 0; i < nr_pages; i++) {
> -                       struct page *page = pvec.pages[i];
> +               for (i = 0; i < nr_folios; i++) {
> +                       struct folio *folio = fbatch.folios[i];
>
>                         /*
>                          * Accumulated enough dirty pages? This doesn't apply
> @@ -2635,10 +2634,10 @@ static int mpage_prepare_extent_to_map(struct mpage_da_data *mpd)
>                                 goto out;
>
>                         /* If we can't merge this page, we are done. */
> -                       if (mpd->map.m_len > 0 && mpd->next_page != page->index)
> +                       if (mpd->map.m_len > 0 && mpd->next_page != folio->index)
>                                 goto out;
>
> -                       lock_page(page);
> +                       folio_lock(folio);
>                         /*
>                          * If the page is no longer dirty, or its mapping no
>                          * longer corresponds to inode we are writing (which
> @@ -2646,16 +2645,16 @@ static int mpage_prepare_extent_to_map(struct mpage_da_data *mpd)
>                          * page is already under writeback and we are not doing
>                          * a data integrity writeback, skip the page
>                          */
> -                       if (!PageDirty(page) ||
> -                           (PageWriteback(page) &&
> +                       if (!folio_test_dirty(folio) ||
> +                           (folio_test_writeback(folio) &&
>                              (mpd->wbc->sync_mode == WB_SYNC_NONE)) ||
> -                           unlikely(page->mapping != mapping)) {
> -                               unlock_page(page);
> +                           unlikely(folio->mapping != mapping)) {
> +                               folio_unlock(folio);
>                                 continue;
>                         }
>
> -                       wait_on_page_writeback(page);
> -                       BUG_ON(PageWriteback(page));
> +                       folio_wait_writeback(folio);
> +                       BUG_ON(folio_test_writeback(folio));
>
>                         /*
>                          * Should never happen but for buggy code in
> @@ -2666,49 +2665,49 @@ static int mpage_prepare_extent_to_map(struct mpage_da_data *mpd)
>                          *
>                          * [1] https://lore.kernel.org/linux-mm/20180103100430.GE4911@quack2.suse.cz
>                          */
> -                       if (!page_has_buffers(page)) {
> -                               ext4_warning_inode(mpd->inode, "page %lu does not have buffers attached", page->index);
> -                               ClearPageDirty(page);
> -                               unlock_page(page);
> +                       if (!folio_buffers(folio)) {
> +                               ext4_warning_inode(mpd->inode, "page %lu does not have buffers attached", folio->index);
> +                               folio_clear_dirty(folio);
> +                               folio_unlock(folio);
>                                 continue;
>                         }
>
>                         if (mpd->map.m_len == 0)
> -                               mpd->first_page = page->index;
> -                       mpd->next_page = page->index + 1;
> +                               mpd->first_page = folio->index;
> +                       mpd->next_page = folio->index + folio_nr_pages(folio);
>                         /*
>                          * Writeout for transaction commit where we cannot
>                          * modify metadata is simple. Just submit the page.
>                          */
>                         if (!mpd->can_map) {
> -                               if (ext4_page_nomap_can_writeout(page)) {
> -                                       err = mpage_submit_page(mpd, page);
> +                               if (ext4_page_nomap_can_writeout(&folio->page)) {
> +                                       err = mpage_submit_page(mpd, &folio->page);
>                                         if (err < 0)
>                                                 goto out;
>                                 } else {
> -                                       unlock_page(page);
> -                                       mpd->first_page++;
> +                                       folio_unlock(folio);
> +                                       mpd->first_page += folio_nr_pages(folio);
>                                 }
>                         } else {
>                                 /* Add all dirty buffers to mpd */
> -                               lblk = ((ext4_lblk_t)page->index) <<
> +                               lblk = ((ext4_lblk_t)folio->index) <<
>                                         (PAGE_SHIFT - blkbits);
> -                               head = page_buffers(page);
> +                               head = folio_buffers(folio);
>                                 err = mpage_process_page_bufs(mpd, head, head,
> -                                                             lblk);
> +                                               lblk);
>                                 if (err <= 0)
>                                         goto out;
>                                 err = 0;
>                         }
> -                       left--;
> +                       left -= folio_nr_pages(folio);
>                 }
> -               pagevec_release(&pvec);
> +               folio_batch_release(&fbatch);
>                 cond_resched();
>         }
>         mpd->scanned_until_end = 1;
>         return 0;
>  out:
> -       pagevec_release(&pvec);
> +       folio_batch_release(&fbatch);
>         return err;
>  }
>
> --
> 2.38.1
>

Could someone review this ext4 patch, please? This is one of the
2 remaining patches that need to be looked at in the series.