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authorAndrea Arcangeli <aarcange@redhat.com>2011-01-14 02:47:20 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-14 04:32:48 +0300
commit22e5c47ee238abe636655c3862ed28d6eb084ad4 (patch)
tree4a4e7d330cbef6c99a8914de482eb0e8daba2485 /include/linux/huge_mm.h
parent29ad768cfc08611a4c1070d0f13f82eeea2bac7b (diff)
downloadlinux-22e5c47ee238abe636655c3862ed28d6eb084ad4.tar.xz
thp: add compound_trans_head() helper
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>
Diffstat (limited to 'include/linux/huge_mm.h')
-rw-r--r--include/linux/huge_mm.h18
1 files changed, 18 insertions, 0 deletions
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index bddfba1d7b85..8e6c8c42bc3c 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -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)
{