From af1500db46b4700ac61a120e88b8e9e359cc17a9 Mon Sep 17 00:00:00 2001
From: Christoph Lameter <clameter@sgi.com>
Date: Wed, 3 Oct 2007 20:42:43 -0700
Subject: [PATCH] vcompound: Smart up virt_to_head_page()

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-2.6.25-rc3-mm1/include/linux/mm.h
===================================================================
--- linux-2.6.25-rc3-mm1.orig/include/linux/mm.h	2008-03-04 16:29:37.937007432 -0800
+++ linux-2.6.25-rc3-mm1/include/linux/mm.h	2008-03-04 16:29:52.704413067 -0800
@@ -262,11 +262,7 @@ 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-2.6.25-rc3-mm1/mm/page_alloc.c
===================================================================
--- linux-2.6.25-rc3-mm1.orig/mm/page_alloc.c	2008-03-04 14:16:33.350333167 -0800
+++ linux-2.6.25-rc3-mm1/mm/page_alloc.c	2008-03-04 16:29:52.704413067 -0800
@@ -174,6 +174,29 @@ static void set_pageblock_migratetype(st
 					PB_migrate, PB_migrate_end);
 }
 
+/*
+ * 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)
 {