linux-kernel - Re: [PATCH] mm,thp: stop leaking unreleased file pages

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Message-ID: <649C7E6B-BD4B-49F6-8CF2-E600AB4B94FF@fb.com>
Date:   Mon, 25 May 2020 00:05:40 +0000
From:   Song Liu <songliubraving@...com>
To:     Hugh Dickins <hughd@...gle.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] mm,thp: stop leaking unreleased file pages



> On May 23, 2020, at 6:50 PM, Hugh Dickins <hughd@...gle.com> wrote:
> 
> When collapse_file() calls try_to_release_page(), it has already
> isolated the page: so if releasing buffers happens to fail (as it
> sometimes does), remember to putback_lru_page(): otherwise that page is
> left unreclaimable and unfreeable, and the file extent uncollapsible.
> 
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
> Cc: stable@...r.kernel.org # v5.4+

Acked-by: Song Liu <songliubraving@...com>

Thanks for the fix!

> ---
> 
> mm/khugepaged.c |    1 +
> 1 file changed, 1 insertion(+)
> 
> --- 5.7-rc6/mm/khugepaged.c	2020-04-12 16:24:37.710999073 -0700
> +++ linux/mm/khugepaged.c	2020-05-10 17:06:21.788398646 -0700
> @@ -1692,6 +1692,7 @@ static void collapse_file(struct mm_stru
> 		if (page_has_private(page) &&
> 		    !try_to_release_page(page, GFP_KERNEL)) {
> 			result = SCAN_PAGE_HAS_PRIVATE;
> +			putback_lru_page(page);
> 			goto out_unlock;
> 		}
>