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thp: remove PG_buddy

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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>
This commit is contained in:
Andrea Arcangeli
2011-01-13 15:47:00 -08:00
committed by Linus Torvalds
parent 21ae5b0175
commit 5f24ce5fd3
7 changed files with 52 additions and 29 deletions
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mm/memory_hotplug.c
+8 -6
View File
@@ -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);
}