[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: 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>

1 files changed, 8 insertions, 8 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5d4c4d02254d..41a3da3d6ccc 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -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)) {