[patch 08/49] hugetlb: pull gigantic page initialisation out of the default path

[Greg KH <gregkh@suse.de>]

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2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Andy Whitcroft <apw@shadowen.org>

commit 18229df5b613ed0732a766fc37850de2e7988e43 upstream

As we can determine exactly when a gigantic page is in use we can optimise
the common regular page cases by pulling out gigantic page initialisation
into its own function.  As gigantic pages are never released to buddy we
do not need a destructor.  This effectivly reverts the previous change to
the main buddy allocator.  It also adds a paranoid check to ensure we
never release gigantic pages from hugetlbfs to the main buddy.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Cc: Jon Tollefson <kniht@linux.vnet.ibm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 mm/hugetlb.c    |   12 +++++++++++-
 mm/internal.h   |    1 +
 mm/page_alloc.c |   28 +++++++++++++++++++++-------
 3 files changed, 33 insertions(+), 8 deletions(-)

--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -455,6 +455,8 @@ static void update_and_free_page(struct 
 {
 	int i;
 
+	VM_BUG_ON(h->order >= MAX_ORDER);
+
 	h->nr_huge_pages--;
 	h->nr_huge_pages_node[page_to_nid(page)]--;
 	for (i = 0; i < pages_per_huge_page(h); i++) {
@@ -969,6 +971,14 @@ found:
 	return 1;
 }
 
+static void prep_compound_huge_page(struct page *page, int order)
+{
+	if (unlikely(order > (MAX_ORDER - 1)))
+		prep_compound_gigantic_page(page, order);
+	else
+		prep_compound_page(page, order);
+}
+
 /* Put bootmem huge pages into the standard lists after mem_map is up */
 static void __init gather_bootmem_prealloc(void)
 {
@@ -979,7 +989,7 @@ static void __init gather_bootmem_preall
 		struct hstate *h = m->hstate;
 		__ClearPageReserved(page);
 		WARN_ON(page_count(page) != 1);
-		prep_compound_page(page, h->order);
+		prep_compound_huge_page(page, h->order);
 		prep_new_huge_page(h, page, page_to_nid(page));
 	}
 }
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -17,6 +17,7 @@ void free_pgtables(struct mmu_gather *tl
 		unsigned long floor, unsigned long ceiling);
 
 extern void prep_compound_page(struct page *page, unsigned long order);
+extern void prep_compound_gigantic_page(struct page *page, unsigned long order);
 
 static inline void set_page_count(struct page *page, int v)
 {
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -268,24 +268,39 @@ void prep_compound_page(struct page *pag
 {
 	int i;
 	int nr_pages = 1 << order;
+
+	set_compound_page_dtor(page, free_compound_page);
+	set_compound_order(page, order);
+	__SetPageHead(page);
+	for (i = 1; i < nr_pages; i++) {
+		struct page *p = page + i;
+
+		__SetPageTail(p);
+		p->first_page = page;
+	}
+}
+
+#ifdef CONFIG_HUGETLBFS
+void prep_compound_gigantic_page(struct page *page, unsigned long order)
+{
+	int i;
+	int nr_pages = 1 << order;
 	struct page *p = page + 1;
 
 	set_compound_page_dtor(page, free_compound_page);
 	set_compound_order(page, order);
 	__SetPageHead(page);
-	for (i = 1; i < nr_pages; i++, p++) {
-		if (unlikely((i & (MAX_ORDER_NR_PAGES - 1)) == 0))
-			p = pfn_to_page(page_to_pfn(page) + i);
+	for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
 		__SetPageTail(p);
 		p->first_page = page;
 	}
 }
+#endif
 
 static void destroy_compound_page(struct page *page, unsigned long order)
 {
 	int i;
 	int nr_pages = 1 << order;
-	struct page *p = page + 1;
 
 	if (unlikely(compound_order(page) != order))
 		bad_page(page);
@@ -293,9 +308,8 @@ static void destroy_compound_page(struct
 	if (unlikely(!PageHead(page)))
 			bad_page(page);
 	__ClearPageHead(page);
-	for (i = 1; i < nr_pages; i++, p++) {
-		if (unlikely((i & (MAX_ORDER_NR_PAGES - 1)) == 0))
-			p = pfn_to_page(page_to_pfn(page) + i);
+	for (i = 1; i < nr_pages; i++) {
+		struct page *p = page + i;
 
 		if (unlikely(!PageTail(p) |
 				(p->first_page != page)))

--