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mm: hwpoison: fix thp split handling in memory_failure()

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When memory_failure() runs on a thp tail page after pmd is split, we
trigger the following VM_BUG_ON_PAGE():

   page:ffffd7cd819b0040 count:0 mapcount:0 mapping:         (null) index:0x1
   flags: 0x1fffc000400000(hwpoison)
   page dumped because: VM_BUG_ON_PAGE(!page_count(p))
   ------------[ cut here ]------------
   kernel BUG at /src/linux-dev/mm/memory-failure.c:1132!

memory_failure() passed refcount and page lock from tail page to head
page, which is not needed because we can pass any subpage to
split_huge_page().

Fixes: 61f5d698cc ("mm: re-enable THP")
Link: http://lkml.kernel.org/r/1477961577-7183-1-git-send-email-n-horiguchi@ah.jp.nec.com
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: <stable@vger.kernel.org>	[4.5+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Naoya Horiguchi 2016-11-10 10:46:23 -08:00 committed by Linus Torvalds
parent dd111be691
commit c3901e722b
1 changed files with 5 additions and 7 deletions
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12
mm/memory-failure.c
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@ -1112,10 +1112,10 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
}
if (!PageHuge(p) && PageTransHuge(hpage)) {
lock_page(hpage);
if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) {
unlock_page(hpage);
if (!PageAnon(hpage))
lock_page(p);
if (!PageAnon(p) || unlikely(split_huge_page(p))) {
unlock_page(p);
if (!PageAnon(p))
pr_err("Memory failure: %#lx: non anonymous thp\n",
pfn);
else
@ -1126,9 +1126,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
put_hwpoison_page(p);
return -EBUSY;
}
unlock_page(hpage);
get_hwpoison_page(p);
put_hwpoison_page(hpage);
unlock_page(p);
VM_BUG_ON_PAGE(!page_count(p), p);
hpage = compound_head(p);
}