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Subject[25/36] compound pages: Allow use of get_page_unless_zero with compound pages
This is needed by slab defragmentation. The refcount of a page head
may be incremented to ensure that a compound page will not go away under us.

It also may be needed for defragmentation of higher order pages. The
moving of compound pages may require the establishment of a reference
before the use of page migration functions.

Signed-off-by: Christoph Lameter <>
include/linux/mm.h | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
Index: linux-2.6/include/linux/mm.h
--- linux-2.6.orig/include/linux/mm.h 2007-08-27 20:59:40.000000000 -0700
+++ linux-2.6/include/linux/mm.h 2007-08-27 21:03:20.000000000 -0700
@@ -290,7 +290,7 @@ static inline int put_page_testzero(stru
static inline int get_page_unless_zero(struct page *page)
- VM_BUG_ON(PageCompound(page));
+ VM_BUG_ON(PageTail(page));
return atomic_inc_not_zero(&page->_count);

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