On 11/22/2017, 01:09 PM, Michal Hocko wrote: > --- a/mm/debug-pagealloc.c > +++ b/mm/debug-pagealloc.c > @@ -34,6 +34,8 @@ static inline void set_page_poison(struct page *page) > struct page_ext *page_ext; > > page_ext = lookup_page_ext(page); > + if (page_ext) > + return; > __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); > } > > @@ -42,6 +44,8 @@ static inline void clear_page_poison(struct page *page) > struct page_ext *page_ext; > > page_ext = lookup_page_ext(page); > + if (page_ext) > + return; > __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); > } > > @@ -50,6 +54,8 @@ static inline bool page_poison(struct page *page) > struct page_ext *page_ext; > > page_ext = lookup_page_ext(page); > + if (page_ext) > + return false; > return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); Now I am confused, your SLE12-SP2's backport in patches.fixes/0001-mm-check-the-return-value-of-lookup_page_ext-for-all.patch does the opposite in all three: + if (!page_ext) + return; thanks, -- js suse labs