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

From: Johannes Weiner
Date: Fri Oct 18 2019 - 12:49:52 EST

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@xxxxxxxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Song Liu <songliubraving@xxxxxx>

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>