mm: more intensive memory corruption debugging

[pandora-kernel.git] / mm / page_alloc.c

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index fa42de7..919d4a1 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -57,6 +57,7 @@
 #include <linux/ftrace_event.h>
 #include <linux/memcontrol.h>
 #include <linux/prefetch.h>
+#include <linux/page-debug-flags.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -410,6 +411,37 @@ static inline void prep_zero_page(struct page *page, int order, gfp_t gfp_flags)
                clear_highpage(page + i);
 }
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
+unsigned int _debug_guardpage_minorder;
+
+static int __init debug_guardpage_minorder_setup(char *buf)
+{
+       unsigned long res;
+
+       if (kstrtoul(buf, 10, &res) < 0 ||  res > MAX_ORDER / 2) {
+               printk(KERN_ERR "Bad debug_guardpage_minorder value\n");
+               return 0;
+       }
+       _debug_guardpage_minorder = res;
+       printk(KERN_INFO "Setting debug_guardpage_minorder to %lu\n", res);
+       return 0;
+}
+__setup("debug_guardpage_minorder=", debug_guardpage_minorder_setup);
+
+static inline void set_page_guard_flag(struct page *page)
+{
+       __set_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags);
+}
+
+static inline void clear_page_guard_flag(struct page *page)
+{
+       __clear_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags);
+}
+#else
+static inline void set_page_guard_flag(struct page *page) { }
+static inline void clear_page_guard_flag(struct page *page) { }
+#endif
+
 static inline void set_page_order(struct page *page, int order)
 {
        set_page_private(page, order);
@@ -467,6 +499,11 @@ static inline int page_is_buddy(struct page *page, struct page *buddy,
        if (page_zone_id(page) != page_zone_id(buddy))
                return 0;
 
+       if (page_is_guard(buddy) && page_order(buddy) == order) {
+               VM_BUG_ON(page_count(buddy) != 0);
+               return 1;
+       }
+
        if (PageBuddy(buddy) && page_order(buddy) == order) {
                VM_BUG_ON(page_count(buddy) != 0);
                return 1;
@@ -523,11 +560,19 @@ static inline void __free_one_page(struct page *page,
                buddy = page + (buddy_idx - page_idx);
                if (!page_is_buddy(page, buddy, order))
                        break;
-
-               /* Our buddy is free, merge with it and move up one order. */
-               list_del(&buddy->lru);
-               zone->free_area[order].nr_free--;
-               rmv_page_order(buddy);
+               /*
+                * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page,
+                * merge with it and move up one order.
+                */
+               if (page_is_guard(buddy)) {
+                       clear_page_guard_flag(buddy);
+                       set_page_private(page, 0);
+                       __mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
+               } else {
+                       list_del(&buddy->lru);
+                       zone->free_area[order].nr_free--;
+                       rmv_page_order(buddy);
+               }
                combined_idx = buddy_idx & page_idx;
                page = page + (combined_idx - page_idx);
                page_idx = combined_idx;
@@ -753,6 +798,23 @@ static inline void expand(struct zone *zone, struct page *page,
                high--;
                size >>= 1;
                VM_BUG_ON(bad_range(zone, &page[size]));
+
+#ifdef CONFIG_DEBUG_PAGEALLOC
+               if (high < debug_guardpage_minorder()) {
+                       /*
+                        * Mark as guard pages (or page), that will allow to
+                        * merge back to allocator when buddy will be freed.
+                        * Corresponding page table entries will not be touched,
+                        * pages will stay not present in virtual address space
+                        */
+                       INIT_LIST_HEAD(&page[size].lru);
+                       set_page_guard_flag(&page[size]);
+                       set_page_private(&page[size], high);
+                       /* Guard pages are not available for any usage */
+                       __mod_zone_page_state(zone, NR_FREE_PAGES, -(1 << high));
+                       continue;
+               }
+#endif
                list_add(&page[size].lru, &area->free_list[migratetype]);
                area->nr_free++;
                set_page_order(&page[size], high);
@@ -1776,7 +1838,8 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...)
 {
        unsigned int filter = SHOW_MEM_FILTER_NODES;
 
-       if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs))
+       if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs) ||
+           debug_guardpage_minorder() > 0)
                return;
 
        /*