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 needed. We use PG_swapcache together with PG_compound
(similar to PageHead() and PageTail()) to signal that a compound
page is virtually mapped. PG_swapcache is not used at this point since
compound pages cannot be put onto the LRU (yet).
Signed-off-by: Christoph Lameter <[email protected]>
---
include/linux/page-flags.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
Index: linux-2.6.25-rc5-mm1/include/linux/page-flags.h
===================================================================
--- linux-2.6.25-rc5-mm1.orig/include/linux/page-flags.h 2008-03-20 17:40:16.141487362 -0700
+++ linux-2.6.25-rc5-mm1/include/linux/page-flags.h 2008-03-20 17:41:58.768233703 -0700
@@ -196,6 +196,24 @@ static inline int PageHighMem(struct pag
}
#endif
+/*
+ * 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
PAGEFLAG(SwapCache, swapcache)
#else
--