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thp: put_page: recheck PageHead after releasing the compound_lock 

After releasing the compound_lock split_huge_page can still run and release the
page before put_page_testzero runs.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrea Arcangeli 2011-01-13 15:46:33 -08:00 committed by Linus Torvalds
parent 9180706344
commit a95a82e96c
1 changed files with 6 additions and 2 deletions
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8
mm/swap.c
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@ -131,8 +131,12 @@ static void put_compound_page(struct page *page)
atomic_dec(&page->_count);
VM_BUG_ON(atomic_read(&page_head->_count) <= 0);
compound_unlock_irqrestore(page_head, flags);
if (put_page_testzero(page_head))
__put_compound_page(page_head);
if (put_page_testzero(page_head)) {
if (PageHead(page_head))
__put_compound_page(page_head);
else
__put_single_page(page_head);
}
} else {
/* page_head is a dangling pointer */
VM_BUG_ON(PageTail(page));