[05/18] Page flags: Add PageVcompound()

Christoph Lameter
2007-10-04T04:01:43Z

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Add a another page flag that can be used to figure out if a compound
page is virtually mapped. The mark is necessary since we have to know
when freeing pages if we have to destroy a virtual mapping. No additional
flag is consumed through the use of PG_swapcache together with PG_compound
(similar to PageHead() and PageTail()).

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
include/linux/page-flags.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

Index: linux-2.6/include/linux/page-flags.h
===================================================================
--- linux-2.6.orig/include/linux/page-flags.h 2007-10-03 19:31:51.000000000 -0700
+++ linux-2.6/include/linux/page-flags.h 2007-10-03 19:34:37.000000000 -0700
@@ -248,6 +248,24 @@ static inline void __ClearPageTail(struc
#define __SetPageHead(page) __SetPageCompound(page)
#define __ClearPageHead(page) __ClearPageCompound(page)

+/*
+ * PG_swapcache is used in combination with PG_compound to indicate
+ * that a compound page was allocated via vmalloc.
+ */
+#define PG_vcompound_mask ((1L << PG_compound) | (1L << PG_swapcache))
+#define PageVcompound(page) ((page->flags & PG_vcompound_mask) \
+ == PG_vcompound_mask)
+
+static inline void __SetPageVcompound(struct page *page)
+{
+ page->flags |= PG_vcompound_mask;
+}
+
+static inline void __ClearPageVcompound(struct page *page)
+{
+ page->flags &= ~PG_vcompound_mask;
+}
+
#ifdef CONFIG_SWAP
#define PageSwapCache(page) test_bit(PG_swapcache, &(page)->flags)
#define SetPageSwapCache(page) set_bit(PG_swapcache, &(page)->flags)

--