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thp: add compound_trans_head() helper

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Cleanup some code with common compound_trans_head helper.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Avi Kivity <avi@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 15:47:20 -08:00
committed by Linus Torvalds
parent 29ad768cfc
commit 22e5c47ee2
3 changed files with 35 additions and 36 deletions
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18
include/linux/huge_mm.h
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@@ -126,6 +126,23 @@ static inline int hpage_nr_pages(struct page *page)
return HPAGE_PMD_NR;
return 1;
}
static inline struct page *compound_trans_head(struct page *page)
{
if (PageTail(page)) {
struct page *head;
head = page->first_page;
smp_rmb();
/*
* head may be a dangling pointer.
* __split_huge_page_refcount clears PageTail before
* overwriting first_page, so if PageTail is still
* there it means the head pointer isn't dangling.
*/
if (PageTail(page))
return head;
}
return page;
}
#else /* CONFIG_TRANSPARENT_HUGEPAGE */
#define HPAGE_PMD_SHIFT ({ BUG(); 0; })
#define HPAGE_PMD_MASK ({ BUG(); 0; })
@@ -144,6 +161,7 @@ static inline int split_huge_page(struct page *page)
do { } while (0)
#define wait_split_huge_page(__anon_vma, __pmd) \
do { } while (0)
#define compound_trans_head(page) compound_head(page)
static inline int hugepage_madvise(struct vm_area_struct *vma,
unsigned long *vm_flags, int advice)
{