From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
David Rientjes <rientjes@google.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: RE: mm: fix BUG in __split_huge_page_pmd
Date: Tue, 15 Oct 2013 14:32:54 +0300 (EEST) [thread overview]
Message-ID: <20131015113254.14E88E0090@blue.fi.intel.com> (raw)
In-Reply-To: <alpine.LNX.2.00.1310150358170.11905@eggly.anvils>
Hugh Dickins wrote:
> Occasionally we hit the BUG_ON(pmd_trans_huge(*pmd)) at the end of
> __split_huge_page_pmd(): seen when doing madvise(,,MADV_DONTNEED).
>
> It's invalid: we don't always have down_write of mmap_sem there:
> a racing do_huge_pmd_wp_page() might have copied-on-write to another
> huge page before our split_huge_page() got the anon_vma lock.
>
> Forget the BUG_ON, just go back and try again if this happens.
>
> Signed-off-by: Hugh Dickins <hughd@google.com>
> Cc: stable@vger.kernel.org
Looks reasonable to me.
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
madvise(MADV_DONTNEED) was aproblematic with THP before. Is a big win having
mmap_sem taken on read rather than on write for it?
--
Kirill A. Shutemov
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next prev parent reply other threads:[~2013-10-15 11:33 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-15 11:08 mm: fix BUG in __split_huge_page_pmd Hugh Dickins
2013-10-15 11:32 ` Kirill A. Shutemov [this message]
2013-10-15 14:41 ` Andrea Arcangeli
2013-10-15 14:34 ` Andrea Arcangeli
2013-10-15 14:48 ` Kirill A. Shutemov
2013-10-15 15:58 ` Andrea Arcangeli
2013-10-15 17:53 ` Hugh Dickins
2013-10-15 18:55 ` Andrea Arcangeli
2013-10-15 19:28 ` Naoya Horiguchi
2013-10-15 19:44 ` Andrea Arcangeli
2013-10-15 20:16 ` Naoya Horiguchi
2013-10-15 20:30 ` Andrea Arcangeli
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