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

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Message-ID: <20200526160140.GC850116@cmpxchg.org>
Date:   Tue, 26 May 2020 12:01:40 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Song Liu <songliubraving@...com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm,thp: stop leaking unreleased file pages

On Sat, May 23, 2020 at 06:50:15PM -0700, Hugh Dickins 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.

Oof, I could imagine that was painful to debug (unless you already
suspected file THP due to a targeted test or similar). Kudos.

> 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: Johannes Weiner <hannes@...xchg.org>