mm, hwpoison: fixup "mm: check the return value of lookup_page_ext for all call sites"

Backport of the upstream commit f86e4271978b ("mm: check the return
value of lookup_page_ext for all call sites") is wrong for hwpoison
pages. I have accidentally negated the condition for bailout. This
basically disables hwpoison pages tracking while the code still
might crash on unusual configurations when struct pages do not have
page_ext allocated. The fix is trivial to invert the condition.

Reported-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/debug-pagealloc.c b/mm/debug-pagealloc.c
index fe1c61f7cf26203d71f3fb12151c34b2b1b831cb..3b8f1b83610eae2fa04f314c900e008a1d380fe5 100644 (file)
--- a/mm/debug-pagealloc.c
+++ b/mm/debug-pagealloc.c
@@ -34,7 +34,7 @@ static inline void set_page_poison(struct page *page)
        struct page_ext *page_ext;
 
        page_ext = lookup_page_ext(page);
-       if (page_ext)
+       if (!page_ext)
                return;
        __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
 }
@@ -44,7 +44,7 @@ static inline void clear_page_poison(struct page *page)
        struct page_ext *page_ext;
 
        page_ext = lookup_page_ext(page);
-       if (page_ext)
+       if (!page_ext)
                return;
        __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
 }
@@ -54,7 +54,7 @@ static inline bool page_poison(struct page *page)
        struct page_ext *page_ext;
 
        page_ext = lookup_page_ext(page);
-       if (page_ext)
+       if (!page_ext)
                return false;
        return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
 }