From: Hugh Dickins <hughd@google.com>
Date: Wed, 16 Oct 2013 20:47:08 +0000 (-0700)
Subject: mm: fix BUG in __split_huge_page_pmd
X-Git-Tag: v3.12-rc6~11^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=750e8165f5e87b6a142be953640eabb13a9d350a;p=pandora-kernel.git

mm: fix BUG in __split_huge_page_pmd

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>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: David Rientjes <rientjes@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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