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[PATCH] mm: VM_BUG_ON
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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: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Nick Piggin authored and Linus Torvalds committed Sep 26, 2006
1 parent a6ca1b9 commit 725d704
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Showing 5 changed files with 36 additions and 29 deletions.
10 changes: 9 additions & 1 deletion include/linux/mm.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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.
*
Expand All @@ -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);
}

Expand All @@ -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);
}

Expand All @@ -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);
}

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4 changes: 2 additions & 2 deletions mm/internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
}

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23 changes: 11 additions & 12 deletions mm/page_alloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
{
Expand Down Expand Up @@ -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);
}
Expand Down Expand Up @@ -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) {
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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);
}
Expand Down Expand Up @@ -809,7 +808,7 @@ static struct page *buffered_rmqueue(struct zonelist *zonelist,
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;
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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);
}
}
Expand Down
12 changes: 6 additions & 6 deletions mm/swap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down Expand Up @@ -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);
}
Expand Down Expand Up @@ -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);
}
Expand All @@ -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);
}
Expand All @@ -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);
}
Expand Down
16 changes: 8 additions & 8 deletions mm/vmscan.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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++;

Expand Down Expand Up @@ -564,7 +564,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
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))
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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))
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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)) {
Expand Down

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