linux-kernel - Re: [PATCHv6 10/22] thp, mm: rewrite delete_from_page

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Date:	Wed, 25 Sep 2013 13:02:36 -0700
From:	Ning Qu <quning@...gle.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Hugh Dickins <hughd@...gle.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Hillf Danton <dhillf@...il.com>, Dave Hansen <dave@...1.net>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv6 10/22] thp, mm: rewrite delete_from_page_cache() to
 support huge pages

Best wishes,
-- 
Ning Qu (曲宁) | Software Engineer | quning@...gle.com | +1-408-418-6066


On Mon, Sep 23, 2013 at 5:05 AM, Kirill A. Shutemov
<kirill.shutemov@...ux.intel.com> wrote:
>
> As with add_to_page_cache_locked() we handle HPAGE_CACHE_NR pages a
> time.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  mm/filemap.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index d2d6c0ebe9..60478ebeda 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -115,6 +115,7 @@
>  void __delete_from_page_cache(struct page *page)
>  {
>         struct address_space *mapping = page->mapping;
> +       int i, nr;
>
>         trace_mm_filemap_delete_from_page_cache(page);
>         /*
> @@ -127,13 +128,20 @@ void __delete_from_page_cache(struct page *page)
>         else
>                 cleancache_invalidate_page(mapping, page);
>
> -       radix_tree_delete(&mapping->page_tree, page->index);
> +       page->mapping = NULL;
Seems with this line added, we clear the page->mapping twice? Once
here and another one after radix_tree_delete. Is this necessary here?

>
> +       nr = hpagecache_nr_pages(page);
> +       for (i = 0; i < nr; i++)
> +               radix_tree_delete(&mapping->page_tree, page->index + i);
> +       /* thp */
> +       if (nr > 1)
> +               __dec_zone_page_state(page, NR_FILE_TRANSPARENT_HUGEPAGES);
> +
>         page->mapping = NULL;
>         /* Leave page->index set: truncation lookup relies upon it */
> -       mapping->nrpages--;
> -       __dec_zone_page_state(page, NR_FILE_PAGES);
> +       mapping->nrpages -= nr;
> +       __mod_zone_page_state(page_zone(page), NR_FILE_PAGES, -nr);
>         if (PageSwapBacked(page))
> -               __dec_zone_page_state(page, NR_SHMEM);
> +               __mod_zone_page_state(page_zone(page), NR_SHMEM, -nr);
>         BUG_ON(page_mapped(page));
>
>         /*
> @@ -144,8 +152,8 @@ void __delete_from_page_cache(struct page *page)
>          * having removed the page entirely.
>          */
>         if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
> -               dec_zone_page_state(page, NR_FILE_DIRTY);
> -               dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
> +               mod_zone_page_state(page_zone(page), NR_FILE_DIRTY, -nr);
> +               add_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE, -nr);
>         }
>  }
>
> --
> 1.8.4.rc3
>
--
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