mm: enable page poisoning early at boot

On SPARSEMEM systems page poisoning is enabled after buddy is up,
because of the dependency on page extension init.  This causes the pages
released by free_all_bootmem not to be poisoned.  This either delays or
misses the identification of some issues because the pages have to
undergo another cycle of alloc-free-alloc for any corruption to be
detected.

Enable page poisoning early by getting rid of the PAGE_EXT_DEBUG_POISON
flag.  Since all the free pages will now be poisoned, the flag need not
be verified before checking the poison during an alloc.

[vinmenon@codeaurora.org: fix Kconfig]
  Link: http://lkml.kernel.org/r/1490878002-14423-1-git-send-email-vinmenon@codeaurora.org
Link: http://lkml.kernel.org/r/1490358246-11001-1-git-send-email-vinmenon@codeaurora.org
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Acked-by: Laura Abbott <labbott@redhat.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 10 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 465391811c2e..f1f225608413 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1689,10 +1689,10 @@ static inline int check_new_page(struct page *page)
         return 1;
 }
 
-static inline bool free_pages_prezeroed(bool poisoned)
+static inline bool free_pages_prezeroed(void)
 {
         return IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) &&
-                page_poisoning_enabled() && poisoned;
+                page_poisoning_enabled();
 }
 
 #ifdef CONFIG_DEBUG_VM
@@ -1746,17 +1746,10 @@ static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags
                                                         unsigned int alloc_flags)
 {
         int i;
-        bool poisoned = true;
-
-        for (i = 0; i < (1 << order); i++) {
-                struct page *p = page + i;
-                if (poisoned)
-                        poisoned &= page_is_poisoned(p);
-        }
 
         post_alloc_hook(page, order, gfp_flags);
 
-        if (!free_pages_prezeroed(poisoned) && (gfp_flags & __GFP_ZERO))
+        if (!free_pages_prezeroed() && (gfp_flags & __GFP_ZERO))
                 for (i = 0; i < (1 << order); i++)
                         clear_highpage(page + i);