Add VM_BUG_ON in case someone uses page_mapping on a slab page
Detect slab objects being passed to the page oriented functions of the VM.
It is not sufficient to simply return NULL because the functions calling
page_mapping may depend on other items of the page_struct also to be setup
properly. Moreover the slab object may not be properly aligned. The page
orientedfunctions of the VM expect to operate on page aligned, page sized
objects. operations on objects straddling page boundaries may only affect
the objects partially which may lead to surprising results.
It is better to detect eventually remaining uses and eliminate them.
Signed-off-by: Christoph Lameter <[email protected]>
---
include/linux/mm.h | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
Index: linux-2.6/include/linux/mm.h
===================================================================
--- linux-2.6.orig/include/linux/mm.h 2007-06-22 10:33:27.000000000 -0700
+++ linux-2.6/include/linux/mm.h 2007-06-22 10:34:09.000000000 -0700
@@ -603,10 +603,7 @@ static inline struct address_space *page
if (unlikely(PageSwapCache(page)))
mapping = &swapper_space;
-#ifdef CONFIG_SLUB
- else if (unlikely(PageSlab(page)))
- mapping = NULL;
-#endif
+ VM_BUG_ON(PageSlab(page));
else if (unlikely((unsigned long)mapping & PAGE_MAPPING_ANON))
mapping = NULL;
return mapping;
-
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