linux-kernel - Re: [PATCH v2] mm,thp: recheck each page before collapsing file THP

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Message-ID: <20191018164943.GA179426@cmpxchg.org>
Date:   Fri, 18 Oct 2019 12:49:43 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Song Liu <songliubraving@...com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, matthew.wilcox@...cle.com,
        kernel-team@...com, william.kucharski@...cle.com,
        kirill.shutemov@...ux.intel.com, Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH v2] mm,thp: recheck each page before collapsing file THP

On Fri, Oct 18, 2019 at 09:37:54AM -0700, Song Liu wrote:
> In collapse_file(), after locking the page, it is necessary to recheck
> that the page is up-to-date. Add PageUptodate() check for both shmem THP
> and file THP.
> 
> Current khugepaged should not try to collapse dirty file THP, because it
> is limited to read only text. Add a PageDirty check and warning for file
> THP. This is added after page_mapping() check, because if the page is
> truncated, it might be dirty.
> 
> Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: William Kucharski <william.kucharski@...cle.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Song Liu <songliubraving@...com>

Acked-by: Johannes Weiner <hannes@...xchg.org>