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Date: Thu, 21 Apr 2016 09:50:21 +1000
From: Stephen Rothwell <sfr@canb.auug.org.au>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andres Lagar-Cavilla <andreslc@google.com>,
        Yang Shi <yang.shi@linaro.org>, Ning Qu <quning@gmail.com>,
        Mika Penttila <mika.penttila@nextfour.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH mmotm 3/5] huge tmpfs recovery: tweak shmem_getpage_gfp
 to fill team fix
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Hi Hugh,

On Sat, 16 Apr 2016 16:33:07 -0700 (PDT) Hugh Dickins <hughd@google.com> wrote:
>
> Please add this fix after my 27/31, your
> huge-tmpfs-recovery-tweak-shmem_getpage_gfp-to-fill-team.patch
> for later merging into it.  Great catch by Mika Penttila, a bug which
> prevented some unusual cases from being recovered into huge pages as
> intended: an initially sparse head would be set PageTeam only after
> this check.  But the check is guarding against a racing disband, which
> cannot happen before the head is published as PageTeam, plus we have
> an additional reference on the head which keeps it safe throughout:
> so very easily fixed.
> 
> Reported-by: Mika Penttila <mika.penttila@nextfour.com>
> Signed-off-by: Hugh Dickins <hughd@google.com>
> ---
>  mm/shmem.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2938,7 +2938,7 @@ repeat:
>  			page = *pagep;
>  			lock_page(page);
>  			head = page - (index & (HPAGE_PMD_NR-1));
> -			if (!PageTeam(head)) {
> +			if (!PageTeam(head) && page != head) {
>  				error = -ENOENT;
>  				goto decused;
>  			}

Added to linux-next today.

-- 
Cheers,
Stephen Rothwell