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mm: hwpoison: drop lru_add_drain_all() in __soft_offline_page()

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A race condition starts to be visible in recent mmotm, where a PG_hwpoison
flag is set on a migration source page *before* it's back in buddy page
poo= l.

This is problematic because no page flag is supposed to be set when
freeing (see __free_one_page().) So the user-visible effect of this race
is that it could trigger the BUG_ON() when soft-offlining is called.

The root cause is that we call lru_add_drain_all() to make sure that the
page is in buddy, but that doesn't work because this function just
schedule= s a work item and doesn't wait its completion.
drain_all_pages() does drainin= g directly, so simply dropping
lru_add_drain_all() solves this problem.

Fixes: f15bdfa802bf ("mm/memory-failure.c: fix memory leak in successful soft offlining")
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Chen Gong <gong.chen@linux.intel.com>
Cc: <stable@vger.kernel.org>	[3.11+]
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 2015-02-12 15:00:25 -08:00 committed by Linus Torvalds
parent 84109e15dd
commit 9ab3b598d2
1 changed files with 0 additions and 2 deletions
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mm/memory-failure.c
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@ -1646,8 +1646,6 @@ static int __soft_offline_page(struct page *page, int flags)
* source page should be freed back to buddy before
* setting PG_hwpoison.
*/
if (!is_free_buddy_page(page))
lru_add_drain_all();
if (!is_free_buddy_page(page))
drain_all_pages(page_zone(page));
SetPageHWPoison(page);