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authorAndrea Arcangeli <aarcange@redhat.com>2011-01-13 15:47:00 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-13 17:32:43 -0800
commit5f24ce5fd34c3ca1b3d10d30da754732da64d5c0 (patch)
treec82d27461f2adda210e77808b7dd04eaec017f2f /mm
parent21ae5b01750f14140809508a478a4413792e0261 (diff)
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thp: remove PG_buddy
PG_buddy can be converted to _mapcount == -2. So the PG_compound_lock can be added to page->flags without overflowing (because of the sparse section bits increasing) with CONFIG_X86_PAE=y and CONFIG_X86_PAT=y. This also has to move the memory hotplug code from _mapcount to lru.next to avoid any risk of clashes. We can't use lru.next for PG_buddy removal, but memory hotplug can use lru.next even more easily than the mapcount instead. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memory_hotplug.c14
-rw-r--r--mm/page_alloc.c7
-rw-r--r--mm/sparse.c4
3 files changed, 13 insertions, 12 deletions
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a2832c092509..e92f04749fcb 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -82,9 +82,10 @@ static void release_memory_resource(struct resource *res)
#ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
#ifndef CONFIG_SPARSEMEM_VMEMMAP
-static void get_page_bootmem(unsigned long info, struct page *page, int type)
+static void get_page_bootmem(unsigned long info, struct page *page,
+ unsigned long type)
{
- atomic_set(&page->_mapcount, type);
+ page->lru.next = (struct list_head *) type;
SetPagePrivate(page);
set_page_private(page, info);
atomic_inc(&page->_count);
@@ -94,15 +95,16 @@ static void get_page_bootmem(unsigned long info, struct page *page, int type)
* so use __ref to tell modpost not to generate a warning */
void __ref put_page_bootmem(struct page *page)
{
- int type;
+ unsigned long type;
- type = atomic_read(&page->_mapcount);
- BUG_ON(type >= -1);
+ type = (unsigned long) page->lru.next;
+ BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
+ type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE);
if (atomic_dec_return(&page->_count) == 1) {
ClearPagePrivate(page);
set_page_private(page, 0);
- reset_page_mapcount(page);
+ INIT_LIST_HEAD(&page->lru);
__free_pages_bootmem(page, 0);
}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e7664b9f706c..9dfe49bceff4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -449,8 +449,8 @@ __find_combined_index(unsigned long page_idx, unsigned int order)
* (c) a page and its buddy have the same order &&
* (d) a page and its buddy are in the same zone.
*
- * For recording whether a page is in the buddy system, we use PG_buddy.
- * Setting, clearing, and testing PG_buddy is serialized by zone->lock.
+ * For recording whether a page is in the buddy system, we set ->_mapcount -2.
+ * Setting, clearing, and testing _mapcount -2 is serialized by zone->lock.
*
* For recording page's order, we use page_private(page).
*/
@@ -483,7 +483,7 @@ static inline int page_is_buddy(struct page *page, struct page *buddy,
* as necessary, plus some accounting needed to play nicely with other
* parts of the VM system.
* At each level, we keep a list of pages, which are heads of continuous
- * free pages of length of (1 << order) and marked with PG_buddy. Page's
+ * free pages of length of (1 << order) and marked with _mapcount -2. Page's
* order is recorded in page_private(page) field.
* So when we are allocating or freeing one, we can derive the state of the
* other. That is, if we allocate a small block, and both were
@@ -5574,7 +5574,6 @@ static struct trace_print_flags pageflag_names[] = {
{1UL << PG_swapcache, "swapcache" },
{1UL << PG_mappedtodisk, "mappedtodisk" },
{1UL << PG_reclaim, "reclaim" },
- {1UL << PG_buddy, "buddy" },
{1UL << PG_swapbacked, "swapbacked" },
{1UL << PG_unevictable, "unevictable" },
#ifdef CONFIG_MMU
diff --git a/mm/sparse.c b/mm/sparse.c
index 95ac219af379..93250207c5cf 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -671,10 +671,10 @@ static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
static void free_map_bootmem(struct page *page, unsigned long nr_pages)
{
unsigned long maps_section_nr, removing_section_nr, i;
- int magic;
+ unsigned long magic;
for (i = 0; i < nr_pages; i++, page++) {
- magic = atomic_read(&page->_mapcount);
+ magic = (unsigned long) page->lru.next;
BUG_ON(magic == NODE_INFO);