[PATCH] debug: check page refcount in __free_pages_ok()

Add a BUG() check to __free_pages_ok() - to catch someone freeing a
page which has a non-zero refcount.  Actually, this check is mainly to
catch someone (ie: shrink_cache()) incrementing a page's refcount
shortly after it has been freed

Also clean up __free_pages_ok() a bit and convert lots of BUGs to BUG_ON.

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9dfd799f219392ae0ea7e58f521645cc1f30c0a4..ce2cfafca0941a49198ee2f8fd39c972a94084b3 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -86,23 +86,24 @@ static void __free_pages_ok (struct page *page, unsigned int order)
        struct page *base;
        zone_t *zone;
 
-       if (PagePrivate(page))
-               BUG();
-       if (page->mapping)
-               BUG();
-       if (PageLocked(page))
-               BUG();
-       if (PageLRU(page))
-               BUG();
-       if (PageActive(page))
-               BUG();
-       if (PageWriteback(page))
-               BUG();
-       ClearPageDirty(page);
-
-       if (current->flags & PF_FREE_PAGES)
-               goto local_freelist;
- back_local_freelist:
+       BUG_ON(PagePrivate(page));
+       BUG_ON(page->mapping != NULL);
+       BUG_ON(PageLocked(page));
+       BUG_ON(PageLRU(page));
+       BUG_ON(PageActive(page));
+       BUG_ON(PageWriteback(page));
+       if (PageDirty(page))
+               ClearPageDirty(page);
+       BUG_ON(page_count(page) != 0);
+
+       if (unlikely(current->flags & PF_FREE_PAGES)) {
+               if (!current->nr_local_pages && !in_interrupt()) {
+                       list_add(&page->list, &current->local_pages);
+                       page->index = order;
+                       current->nr_local_pages++;
+                       goto out;
+               }
+       }
 
        zone = page_zone(page);
 
@@ -112,18 +113,14 @@ static void __free_pages_ok (struct page *page, unsigned int order)
        if (page_idx & ~mask)
                BUG();
        index = page_idx >> (1 + order);
-
        area = zone->free_area + order;
 
        spin_lock_irqsave(&zone->lock, flags);
-
        zone->free_pages -= mask;
-
        while (mask + (1 << (MAX_ORDER-1))) {
                struct page *buddy1, *buddy2;
 
-               if (area >= zone->free_area + MAX_ORDER)
-                       BUG();
+               BUG_ON(area >= zone->free_area + MAX_ORDER);
                if (!__test_and_change_bit(index, area->map))
                        /*
                         * the buddy page is still allocated.
@@ -136,11 +133,8 @@ static void __free_pages_ok (struct page *page, unsigned int order)
                 */
                buddy1 = base + (page_idx ^ -mask);
                buddy2 = base + page_idx;
-               if (bad_range(zone, buddy1))
-                       BUG();
-               if (bad_range(zone, buddy2))
-                       BUG();
-
+               BUG_ON(bad_range(zone, buddy1));
+               BUG_ON(bad_range(zone, buddy2));
                list_del(&buddy1->list);
                mask <<= 1;
                area++;
@@ -148,19 +142,9 @@ static void __free_pages_ok (struct page *page, unsigned int order)
                page_idx &= mask;
        }
        list_add(&(base + page_idx)->list, &area->free_list);
-
        spin_unlock_irqrestore(&zone->lock, flags);
+out:
        return;
-
- local_freelist:
-       if (current->nr_local_pages)
-               goto back_local_freelist;
-       if (in_interrupt())
-               goto back_local_freelist;               
-
-       list_add(&page->list, &current->local_pages);
-       page->index = order;
-       current->nr_local_pages++;
 }
 
 #define MARK_USED(index, order, area) \
@@ -172,8 +156,7 @@ static inline struct page * expand (zone_t *zone, struct page *page,
        unsigned long size = 1 << high;
 
        while (high > low) {
-               if (bad_range(zone, page))
-                       BUG();
+               BUG_ON(bad_range(zone, page));
                area--;
                high--;
                size >>= 1;
@@ -182,8 +165,7 @@ static inline struct page * expand (zone_t *zone, struct page *page,
                index += size;
                page += size;
        }
-       if (bad_range(zone, page))
-               BUG();
+       BUG_ON(bad_range(zone, page));
        return page;
 }
 
@@ -223,8 +205,7 @@ static struct page * rmqueue(zone_t *zone, unsigned int order)
                        unsigned int index;
 
                        page = list_entry(curr, struct page, list);
-                       if (bad_range(zone, page))
-                               BUG();
+                       BUG_ON(bad_range(zone, page));
                        list_del(curr);
                        index = page - zone->zone_mem_map;
                        if (curr_order != MAX_ORDER-1)
@@ -279,14 +260,14 @@ struct page *_alloc_pages(unsigned int gfp_mask, unsigned int order)
 }
 #endif
 
-static struct page * FASTCALL(balance_classzone(zone_t *, unsigned int, unsigned int, int *));
-static struct page * balance_classzone(zone_t * classzone, unsigned int gfp_mask, unsigned int order, int * freed)
+static /* inline */ struct page *
+balance_classzone(zone_t * classzone, unsigned int gfp_mask,
+                       unsigned int order, int * freed)
 {
        struct page * page = NULL;
        int __freed = 0;
 
-       if (in_interrupt())
-               BUG();
+       BUG_ON(in_interrupt());
 
        current->allocation_order = order;
        current->flags |= PF_MEMALLOC | PF_FREE_PAGES;
@@ -793,8 +774,7 @@ void __init free_area_init_core(int nid, pg_data_t *pgdat, struct page **gmap,
        unsigned long totalpages, offset, realtotalpages;
        const unsigned long zone_required_alignment = 1UL << (MAX_ORDER-1);
 
-       if (zone_start_paddr & ~PAGE_MASK)
-               BUG();
+       BUG_ON(zone_start_paddr & ~PAGE_MASK);
 
        totalpages = 0;
        for (i = 0; i < MAX_NR_ZONES; i++) {