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Date: Tue, 8 Jan 2013 20:03:02 +0200
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Hillf Danton <dhillf@gmail.com>, Hugh Dickins <hughd@google.com>,
        Dave Jones <davej@redhat.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        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: <20130108180302.GA27871@shutemov.name>
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On Tue, Jan 08, 2013 at 06:49:51PM +0100, Andrea Arcangeli wrote:
> Hi Kirill,
> 
> On Tue, Jan 08, 2013 at 07:30:58PM +0200, Kirill A. Shutemov wrote:
> > Merged patch is obviously broken: huge_pmd_set_accessed() can be called
> > only if the pmd is under splitting.
> 
> Of course I assume you meant "only if the pmd is not under splitting".

The broken merged patch has this:

+                       if (dirty && !pmd_write(orig_pmd) &&
                            !pmd_trans_splitting(orig_pmd)) {
			[...]
+                       } else {
+                               huge_pmd_set_accessed(mm, vma, address, pmd,
+                                                     orig_pmd, dirty);
                        }

> But no, setting a bitflag like the young bit or clearing or setting
> the numa bit won't screw with split_huge_page and it's safe even if
> the pmd is under splitting.

Okay. Thanks for clarification for me.

-- 
 Kirill A. Shutemov