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Date: Tue, 8 Jan 2013 19:30:58 +0200
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Hillf Danton <dhillf@gmail.com>, Hugh Dickins <hughd@google.com>,
        Dave Jones <davej@redhat.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@suse.de>, Linux-MM <linux-mm@kvack.org>,
        Rik van Riel <riel@redhat.com>
Subject: Re: oops in copy_page_rep()
Message-ID: <20130108173058.GA27727@shutemov.name>
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On Tue, Jan 08, 2013 at 08:52:14AM -0800, Linus Torvalds wrote:
> On Tue, Jan 8, 2013 at 8:31 AM, Kirill A. Shutemov <kirill@shutemov.name> wrote:
> >>
> >> Heh. I was more thinking about why do_huge_pmd_wp_page() needs it, but
> >> do_huge_pmd_numa_page() does not.
> >
> > It does. The check should be moved up.
> >
> >> Also, do we actually need it for huge_pmd_set_accessed()? The
> >> *placement* of that thing confuses me. And because it confuses me, I'd
> >> like to understand it.
> >
> > We need it for huge_pmd_set_accessed() too.
> >
> > Looks like a mis-merge. The original patch for huge_pmd_set_accessed() was
> > correct: http://lkml.org/lkml/2012/10/25/402
> 
> Not a merge error: the pmd_trans_splitting() check was removed by
> commit d10e63f29488 ("mm: numa: Create basic numa page hinting
> infrastructure").

Check difference between patch above and merged one -- a1dd450.
Merged patch is obviously broken: huge_pmd_set_accessed() can be called
only if the pmd is under splitting.

-- 
 Kirill A. Shutemov