mm: page_alloc: ignore init_on_free=1 for debug_pagealloc=1

On !ARCH_SUPPORTS_DEBUG_PAGEALLOC (like ia64) debug_pagealloc=1 implies
page_poison=on:

    if (page_poisoning_enabled() ||
         (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
          debug_pagealloc_enabled()))
            static_branch_enable(&_page_poisoning_enabled);

page_poison=on needs to override init_on_free=1.

Before the change it did not work as expected for the following case:
- have PAGE_POISONING=y
- have page_poison unset
- have !ARCH_SUPPORTS_DEBUG_PAGEALLOC arch (like ia64)
- have init_on_free=1
- have debug_pagealloc=1

That way we get both keys enabled:
- static_branch_enable(&init_on_free);
- static_branch_enable(&_page_poisoning_enabled);

which leads to poisoned pages returned for __GFP_ZERO pages.

After the change we execute only:
- static_branch_enable(&_page_poisoning_enabled);
  and ignore init_on_free=1.

Link: https://lkml.kernel.org/r/20210329222555.3077928-1-slyfox@gentoo.org
Link: https://lkml.org/lkml/2021/3/26/443
Fixes: 8db26a3d4735 ("mm, page_poison: use static key more efficiently")
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 91455f0d22c12e3e155b2529633ac0a7bfb47a1f..6b208b1843bf0eb3574033d08c8ca382442b0324 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -786,32 +786,36 @@ static inline void clear_page_guard(struct zone *zone, struct page *page,
  */
 void init_mem_debugging_and_hardening(void)
 {
+       bool page_poisoning_requested = false;
+
+#ifdef CONFIG_PAGE_POISONING
+       /*
+        * Page poisoning is debug page alloc for some arches. If
+        * either of those options are enabled, enable poisoning.
+        */
+       if (page_poisoning_enabled() ||
+            (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
+             debug_pagealloc_enabled())) {
+               static_branch_enable(&_page_poisoning_enabled);
+               page_poisoning_requested = true;
+       }
+#endif
+
        if (_init_on_alloc_enabled_early) {
-               if (page_poisoning_enabled())
+               if (page_poisoning_requested)
                        pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
                                "will take precedence over init_on_alloc\n");
                else
                        static_branch_enable(&init_on_alloc);
        }
        if (_init_on_free_enabled_early) {
-               if (page_poisoning_enabled())
+               if (page_poisoning_requested)
                        pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
                                "will take precedence over init_on_free\n");
                else
                        static_branch_enable(&init_on_free);
        }
 
-#ifdef CONFIG_PAGE_POISONING
-       /*
-        * Page poisoning is debug page alloc for some arches. If
-        * either of those options are enabled, enable poisoning.
-        */
-       if (page_poisoning_enabled() ||
-            (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
-             debug_pagealloc_enabled()))
-               static_branch_enable(&_page_poisoning_enabled);
-#endif
-
 #ifdef CONFIG_DEBUG_PAGEALLOC
        if (!debug_pagealloc_enabled())
                return;