From: Christoph Lameter Date: Tue, 17 Jul 2007 11:03:33 +0000 (-0700) Subject: Add VM_BUG_ON in case someone uses page_mapping on a slab page X-Git-Tag: v2.6.23-rc1~731 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b5fab14e5d87df4d94161ae5f5e0c8625f9ffda2;p=linux-2.6 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 slab object may not be properly aligned. The page oriented functions of the VM expect to operate on page aligned, page sized objects. Operations on object 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 Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/include/linux/mm.h b/include/linux/mm.h index 4c482a3ee8..a5c451816f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -599,6 +599,7 @@ static inline struct address_space *page_mapping(struct page *page) { struct address_space *mapping = page->mapping; + VM_BUG_ON(PageSlab(page)); if (unlikely(PageSwapCache(page))) mapping = &swapper_space; #ifdef CONFIG_SLUB