[04/18] Vcompound: Smart up virt_to_head_page()

Christoph Lameter
2007-10-04T04:01:57Z

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The determination of a page struct for an address in a compound page
will need some more smarts in order to deal with virtual addresses.

We need to use the evil constants VMALLOC_START and VMALLOC_END for this
and they are notoriously for referencing various arch header files or may
even be variables. Uninline the function to avoid trouble.

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

---
include/linux/mm.h | 6 +-----
mm/page_alloc.c | 23 +++++++++++++++++++++++
2 files changed, 24 insertions(+), 5 deletions(-)

Index: linux-2.6/include/linux/mm.h
===================================================================
--- linux-2.6.orig/include/linux/mm.h 2007-10-03 19:21:50.000000000 -0700
+++ linux-2.6/include/linux/mm.h 2007-10-03 19:23:08.000000000 -0700
@@ -315,11 +315,7 @@ static inline void get_page(struct page
atomic_inc(&page->_count);
}

-static inline struct page *virt_to_head_page(const void *x)
-{
- struct page *page = virt_to_page(x);
- return compound_head(page);
-}
+struct page *virt_to_head_page(const void *x);

/*
* Setup the page count before being freed into the page allocator for
Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c 2007-10-03 19:21:50.000000000 -0700
+++ linux-2.6/mm/page_alloc.c 2007-10-03 19:23:08.000000000 -0700
@@ -150,6 +150,29 @@ int nr_node_ids __read_mostly = MAX_NUMN
EXPORT_SYMBOL(nr_node_ids);
#endif

+/*
+ * Determine the appropriate page struct given a virtual address
+ * (including vmalloced areas).
+ *
+ * Return the head page if this is a compound page.
+ *
+ * Cannot be inlined since VMALLOC_START and VMALLOC_END may contain
+ * complex calculations that depend on multiple arch includes or
+ * even variables.
+ */
+struct page *virt_to_head_page(const void *x)
+{
+ unsigned long addr = (unsigned long)x;
+ struct page *page;
+
+ if (unlikely(addr >= VMALLOC_START && addr < VMALLOC_END))
+ page = vmalloc_to_page((void *)addr);
+ else
+ page = virt_to_page(addr);
+
+ return compound_head(page);
+}
+
#ifdef CONFIG_DEBUG_VM
static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
{

--