On Mon, Nov 26, 2018 at 03:21:58PM -0800, Hugh Dickins wrote:
> Huge tmpfs testing, on 32-bit kernel with lockdep enabled, showed that
> __split_huge_page() was using i_size_read() while holding the irq-safe
> lru_lock and page tree lock, but the 32-bit i_size_read() uses an
> irq-unsafe seqlock which should not be nested inside them.
>
> Instead, read the i_size earlier in split_huge_page_to_list(), and pass
> the end offset down to __split_huge_page(): all while holding head page
> lock, which is enough to prevent truncation of that extent before the
> page tree lock has been taken.
>
> Fixes: baa355fd33142 ("thp: file pages support for split_huge_page()")
> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # 4.8+
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
--
Kirill A. Shutemov
