Commit a3af9c38 authored Jun 16, 2009 by Nick Piggin Committed by Linus Torvalds Jun 16, 2009

page allocator: do not check for compound pages during the page allocator sanity checks



A number of sanity checks are made on each page allocation and free
including that the page count is zero.  page_count() checks for compound
pages and checks the count of the head page if true.  However, in these
paths, we do not care if the page is compound or not as the count of each
tail page should also be zero.

This patch makes two changes to the use of page_count() in the free path.
It converts one check of page_count() to a VM_BUG_ON() as the count should
have been unconditionally checked earlier in the free path.  It also
avoids checking for compound pages.

[mel@csn.ul.ie: Wrote changelog]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent d395b734

mm/page_alloc.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -421,7 +421,7 @@ static inline int page_is_buddy(struct page page, struct page buddy,
		return 0;

		if (PageBuddy(buddy) && page_order(buddy) == order) {
		BUG_ON(page_count(buddy) != 0);
		VM_BUG_ON(page_count(buddy) != 0);
		return 1;
		}
		return 0;
		@@ -497,7 +497,7 @@ static inline int free_pages_check(struct page *page)
		{
		if (unlikely(page_mapcount(page) \|
		(page->mapping != NULL) \|
		(page_count(page) != 0) \|
		(atomic_read(&page->_count) != 0) \|
		(page->flags & PAGE_FLAGS_CHECK_AT_FREE))) {
		bad_page(page);
		return 1;
		@@ -642,7 +642,7 @@ static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
		{
		if (unlikely(page_mapcount(page) \|
		(page->mapping != NULL) \|
		(page_count(page) != 0) \|
		(atomic_read(&page->_count) != 0) \|
		(page->flags & PAGE_FLAGS_CHECK_AT_PREP))) {
		bad_page(page);
		return 1;

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