On 27.03.21 19:21, 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 init_on_free=1.
Before the change id happened too late 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.
CC: Vlastimil Babka <vba...@suse.cz>
CC: Andrew Morton <a...@linux-foundation.org>
CC: linux...@kvack.org
CC: David Hildenbrand <da...@redhat.com>
CC: Andrey Konovalov <andreyk...@gmail.com>
Link: https://lkml.org/lkml/2021/3/26/443
Again, Fixes: tag? IOW, which commit initially broke it.
Signed-off-by: Sergei Trofimovich <sly...@gentoo.org>
---
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 d57d9b4f7089..10a8a1d28c11 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_poison_requested = page_poisoning_enabled();
s/page_poison_requested/page_poisoning_requested/
And I wonder if you should just initialize to "false" here.
Without CONFIG_PAGE_POISONING, page_poisoning_enabled() will always
return false, so it seems unnecessary.
+
+#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_poison_requested = true;
+ }
+#endif
Apart from that, looks good.
--
Thanks,
David / dhildenb
