On 30.03.21 00:25, Sergei Trofimovich wrote:
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.
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Fixes: 8db26a3d4735 ("mm, page_poison: use static key more efficiently")
Cc: <stable@xxxxxxxxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: linux-mm@xxxxxxxxx
CC: David Hildenbrand <david@xxxxxxxxxx>
CC: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Link: https://lkml.org/lkml/2021/3/26/443
Signed-off-by: Sergei Trofimovich <slyfox@xxxxxxxxxx>
---
Change since v2:
- Added 'Fixes:' and 'CC: stable@' suggested by Vlastimil and David
- Renamed local variable to 'page_poisoning_requested' for
consistency suggested by David
- Simplified initialization of page_poisoning_requested suggested
by David
- Added 'Acked-by: Vlastimil'
mm/page_alloc.c | 30 +++++++++++++++++-------------
1 file changed, 17 insertions(+), 13 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cfc72873961d..4bb3cdfc47f8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -764,32 +764,36 @@ 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;
Thanks!
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
