Commit 725d704e authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

[PATCH] mm: VM_BUG_ON 



Introduce a VM_BUG_ON, which is turned on with CONFIG_DEBUG_VM.  Use this
in the lightweight, inline refcounting functions; PageLRU and PageActive
checks in vmscan, because they're pretty well confined to vmscan.  And in
page allocate/free fastpaths which can be the hottest parts of the kernel
for kbuilds.

Unlike BUG_ON, VM_BUG_ON must not be used to execute statements with
side-effects, and should not be used outside core mm code.

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a6ca1b99

include/linux/mm.h

+9 −1
Original line number Diff line number Diff line
@@ -278,6 +278,12 @@ struct page { 
 */

#include <linux/page-flags.h>



#ifdef CONFIG_DEBUG_VM

#define VM_BUG_ON(cond) BUG_ON(cond)

#else

#define VM_BUG_ON(condition) do { } while(0)

#endif



/*

 * Methods to modify the page usage count.

 *
@@ -297,7 +303,7 @@ struct page { 
 */

static inline int put_page_testzero(struct page *page)

{

	BUG_ON(atomic_read(&page->_count) == 0);

	VM_BUG_ON(atomic_read(&page->_count) == 0);

	return atomic_dec_and_test(&page->_count);

}
@@ -307,6 +313,7 @@ static inline int put_page_testzero(struct page *page) 
 */

static inline int get_page_unless_zero(struct page *page)

{

	VM_BUG_ON(PageCompound(page));

	return atomic_inc_not_zero(&page->_count);

}
@@ -323,6 +330,7 @@ static inline void get_page(struct page *page) 
{

	if (unlikely(PageCompound(page)))

		page = (struct page *)page_private(page);

	VM_BUG_ON(atomic_read(&page->_count) == 0);

	atomic_inc(&page->_count);

}

mm/internal.h

+2 −2
Original line number Diff line number Diff line
@@ -24,8 +24,8 @@ static inline void set_page_count(struct page *page, int v) 
 */

static inline void set_page_refcounted(struct page *page)

{

	BUG_ON(PageCompound(page) && page_private(page) != (unsigned long)page);

	BUG_ON(atomic_read(&page->_count));

	VM_BUG_ON(PageCompound(page) && page_private(page) != (unsigned long)page);

	VM_BUG_ON(atomic_read(&page->_count));

	set_page_count(page, 1);

}

mm/page_alloc.c

+11 −12
Original line number Diff line number Diff line
@@ -127,7 +127,6 @@ static int bad_range(struct zone *zone, struct page *page) 


	return 0;

}



#else

static inline int bad_range(struct zone *zone, struct page *page)

{
@@ -218,12 +217,12 @@ static inline void prep_zero_page(struct page *page, int order, gfp_t gfp_flags) 
{

	int i;



	BUG_ON((gfp_flags & (__GFP_WAIT | __GFP_HIGHMEM)) == __GFP_HIGHMEM);

	VM_BUG_ON((gfp_flags & (__GFP_WAIT | __GFP_HIGHMEM)) == __GFP_HIGHMEM);

	/*

	 * clear_highpage() will use KM_USER0, so it's a bug to use __GFP_ZERO

	 * and __GFP_HIGHMEM from hard or soft interrupt context.

	 */

	BUG_ON((gfp_flags & __GFP_HIGHMEM) && in_interrupt());

	VM_BUG_ON((gfp_flags & __GFP_HIGHMEM) && in_interrupt());

	for (i = 0; i < (1 << order); i++)

		clear_highpage(page + i);

}
@@ -347,8 +346,8 @@ static inline void __free_one_page(struct page *page, 


	page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);



	BUG_ON(page_idx & (order_size - 1));

	BUG_ON(bad_range(zone, page));

	VM_BUG_ON(page_idx & (order_size - 1));

	VM_BUG_ON(bad_range(zone, page));



	zone->free_pages += order_size;

	while (order < MAX_ORDER-1) {
@@ -421,7 +420,7 @@ static void free_pages_bulk(struct zone *zone, int count, 
	while (count--) {

		struct page *page;



		BUG_ON(list_empty(list));

		VM_BUG_ON(list_empty(list));

		page = list_entry(list->prev, struct page, lru);

		/* have to delete it as __free_one_page list manipulates */

		list_del(&page->lru);
@@ -512,7 +511,7 @@ static inline void expand(struct zone *zone, struct page *page, 
		area--;

		high--;

		size >>= 1;

		BUG_ON(bad_range(zone, &page[size]));

		VM_BUG_ON(bad_range(zone, &page[size]));

		list_add(&page[size].lru, &area->free_list);

		area->nr_free++;

		set_page_order(&page[size], high);
@@ -761,8 +760,8 @@ void split_page(struct page *page, unsigned int order) 
{

	int i;



	BUG_ON(PageCompound(page));

	BUG_ON(!page_count(page));

	VM_BUG_ON(PageCompound(page));

	VM_BUG_ON(!page_count(page));

	for (i = 1; i < (1 << order); i++)

		set_page_refcounted(page + i);

}
@@ -809,7 +808,7 @@ again: 
	local_irq_restore(flags);

	put_cpu();



	BUG_ON(bad_range(zone, page));

	VM_BUG_ON(bad_range(zone, page));

	if (prep_new_page(page, order, gfp_flags))

		goto again;

	return page;
@@ -1083,7 +1082,7 @@ fastcall unsigned long get_zeroed_page(gfp_t gfp_mask) 
	 * get_zeroed_page() returns a 32-bit address, which cannot represent

	 * a highmem page

	 */

	BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);

	VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);



	page = alloc_pages(gfp_mask | __GFP_ZERO, 0);

	if (page)
@@ -1116,7 +1115,7 @@ EXPORT_SYMBOL(__free_pages); 
fastcall void free_pages(unsigned long addr, unsigned int order)

{

	if (addr != 0) {

		BUG_ON(!virt_addr_valid((void *)addr));

		VM_BUG_ON(!virt_addr_valid((void *)addr));

		__free_pages(virt_to_page((void *)addr), order);

	}

}

mm/swap.c

+6 −6
Original line number Diff line number Diff line
@@ -233,7 +233,7 @@ void fastcall __page_cache_release(struct page *page) 
		struct zone *zone = page_zone(page);



		spin_lock_irqsave(&zone->lru_lock, flags);

		BUG_ON(!PageLRU(page));

		VM_BUG_ON(!PageLRU(page));

		__ClearPageLRU(page);

		del_page_from_lru(zone, page);

		spin_unlock_irqrestore(&zone->lru_lock, flags);
@@ -284,7 +284,7 @@ void release_pages(struct page **pages, int nr, int cold) 
				zone = pagezone;

				spin_lock_irq(&zone->lru_lock);

			}

			BUG_ON(!PageLRU(page));

			VM_BUG_ON(!PageLRU(page));

			__ClearPageLRU(page);

			del_page_from_lru(zone, page);

		}
@@ -337,7 +337,7 @@ void __pagevec_release_nonlru(struct pagevec *pvec) 
	for (i = 0; i < pagevec_count(pvec); i++) {

		struct page *page = pvec->pages[i];



		BUG_ON(PageLRU(page));

		VM_BUG_ON(PageLRU(page));

		if (put_page_testzero(page))

			pagevec_add(&pages_to_free, page);

	}
@@ -364,7 +364,7 @@ void __pagevec_lru_add(struct pagevec *pvec) 
			zone = pagezone;

			spin_lock_irq(&zone->lru_lock);

		}

		BUG_ON(PageLRU(page));

		VM_BUG_ON(PageLRU(page));

		SetPageLRU(page);

		add_page_to_inactive_list(zone, page);

	}
@@ -391,9 +391,9 @@ void __pagevec_lru_add_active(struct pagevec *pvec) 
			zone = pagezone;

			spin_lock_irq(&zone->lru_lock);

		}

		BUG_ON(PageLRU(page));

		VM_BUG_ON(PageLRU(page));

		SetPageLRU(page);

		BUG_ON(PageActive(page));

		VM_BUG_ON(PageActive(page));

		SetPageActive(page);

		add_page_to_active_list(zone, page);

	}

mm/vmscan.c

+8 −8
Original line number Diff line number Diff line
@@ -440,7 +440,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, 
		if (TestSetPageLocked(page))

			goto keep;



		BUG_ON(PageActive(page));

		VM_BUG_ON(PageActive(page));



		sc->nr_scanned++;
@@ -564,7 +564,7 @@ keep_locked: 
		unlock_page(page);

keep:

		list_add(&page->lru, &ret_pages);

		BUG_ON(PageLRU(page));

		VM_BUG_ON(PageLRU(page));

	}

	list_splice(&ret_pages, page_list);

	if (pagevec_count(&freed_pvec))
@@ -603,7 +603,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 
		page = lru_to_page(src);

		prefetchw_prev_lru_page(page, src, flags);



		BUG_ON(!PageLRU(page));

		VM_BUG_ON(!PageLRU(page));



		list_del(&page->lru);

		target = src;
@@ -674,7 +674,7 @@ static unsigned long shrink_inactive_list(unsigned long max_scan, 
		 */

		while (!list_empty(&page_list)) {

			page = lru_to_page(&page_list);

			BUG_ON(PageLRU(page));

			VM_BUG_ON(PageLRU(page));

			SetPageLRU(page);

			list_del(&page->lru);

			if (PageActive(page))
@@ -797,9 +797,9 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 
	while (!list_empty(&l_inactive)) {

		page = lru_to_page(&l_inactive);

		prefetchw_prev_lru_page(page, &l_inactive, flags);

		BUG_ON(PageLRU(page));

		VM_BUG_ON(PageLRU(page));

		SetPageLRU(page);

		BUG_ON(!PageActive(page));

		VM_BUG_ON(!PageActive(page));

		ClearPageActive(page);



		list_move(&page->lru, &zone->inactive_list);
@@ -827,9 +827,9 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 
	while (!list_empty(&l_active)) {

		page = lru_to_page(&l_active);

		prefetchw_prev_lru_page(page, &l_active, flags);

		BUG_ON(PageLRU(page));

		VM_BUG_ON(PageLRU(page));

		SetPageLRU(page);

		BUG_ON(!PageActive(page));

		VM_BUG_ON(!PageActive(page));

		list_move(&page->lru, &zone->active_list);

		pgmoved++;

		if (!pagevec_add(&pvec, page)) {

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