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Message-Id: <20201026173358.14704-3-vbabka@suse.cz>
Date: Mon, 26 Oct 2020 18:33:57 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Alexander Potapenko <glider@...gle.com>,
Kees Cook <keescook@...omium.org>,
Michal Hocko <mhocko@...nel.org>,
David Hildenbrand <david@...hat.com>,
Mateusz Nosek <mateusznosek0@...il.com>,
Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 2/3] mm, page_poison: use static key more efficiently
Commit 11c9c7edae06 ("mm/page_poison.c: replace bool variable with static key")
changed page_poisoning_enabled() to a static key check. However, the function
is not inlined, so each check still involves a function call with overhead not
eliminated when page poisoning is disabled.
Analogically to how debug_pagealloc is handled, this patch converts
page_poisoning_enabled() back to boolean check, and introduces
page_poisoning_enabled_static() for fast paths. Both functions are inlined.
Also optimize the check that enables page poisoning instead of debug_pagealloc
for architectures without proper debug_pagealloc support. Move the check to
init_mem_debugging() to enable a single static key instead of having two
static branches in page_poisoning_enabled_static().
Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
drivers/virtio/virtio_balloon.c | 2 +-
include/linux/mm.h | 16 ++++++++++++-
mm/page_alloc.c | 13 ++++++++++-
mm/page_poison.c | 40 +++++----------------------------
4 files changed, 34 insertions(+), 37 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 481611c09dae..e53faed6ba93 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -1116,7 +1116,7 @@ static int virtballoon_validate(struct virtio_device *vdev)
*/
if (!want_init_on_free() &&
(IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) ||
- !page_poisoning_enabled()))
+ !page_poisoning_enabled_static()))
__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON))
__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c6a0adccf2fe..c1d0ed2b8724 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2867,10 +2867,24 @@ extern int apply_to_existing_page_range(struct mm_struct *mm,
extern void init_mem_debugging(void);
#ifdef CONFIG_PAGE_POISONING
-extern bool page_poisoning_enabled(void);
extern void kernel_poison_pages(struct page *page, int numpages, int enable);
+extern bool _page_poisoning_enabled_early;
+DECLARE_STATIC_KEY_FALSE(_page_poisoning_enabled);
+static inline bool page_poisoning_enabled(void)
+{
+ return _page_poisoning_enabled_early;
+}
+/*
+ * For use in fast paths after init_mem_debugging() has run, or when a
+ * false negative result is not harmful when called too early.
+ */
+static inline bool page_poisoning_enabled_static(void)
+{
+ return (static_branch_unlikely(&_page_poisoning_enabled));
+}
#else
static inline bool page_poisoning_enabled(void) { return false; }
+static inline bool page_poisoning_enabled_static(void) { return false; }
static inline void kernel_poison_pages(struct page *page, int numpages,
int enable) { }
#endif
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b168c58ef337..2a1be197649d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -777,6 +777,17 @@ void init_mem_debugging()
}
}
+#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;
@@ -2208,7 +2219,7 @@ static inline int check_new_page(struct page *page)
static inline bool free_pages_prezeroed(void)
{
return (IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) &&
- page_poisoning_enabled()) || want_init_on_free();
+ page_poisoning_enabled_static()) || want_init_on_free();
}
#ifdef CONFIG_DEBUG_VM
diff --git a/mm/page_poison.c b/mm/page_poison.c
index ae0482cded87..d1f06b70a779 100644
--- a/mm/page_poison.c
+++ b/mm/page_poison.c
@@ -8,45 +8,17 @@
#include <linux/ratelimit.h>
#include <linux/kasan.h>
-static DEFINE_STATIC_KEY_FALSE_RO(want_page_poisoning);
+bool _page_poisoning_enabled_early;
+EXPORT_SYMBOL(_page_poisoning_enabled_early);
+DEFINE_STATIC_KEY_FALSE_RO(_page_poisoning_enabled);
+EXPORT_SYMBOL(_page_poisoning_enabled);
static int __init early_page_poison_param(char *buf)
{
- int ret;
- bool tmp;
-
- ret = strtobool(buf, &tmp);
- if (ret)
- return ret;
-
- if (tmp)
- static_branch_enable(&want_page_poisoning);
- else
- static_branch_disable(&want_page_poisoning);
-
- return 0;
+ return kstrtobool(buf, &_page_poisoning_enabled_early);
}
early_param("page_poison", early_page_poison_param);
-/**
- * page_poisoning_enabled - check if page poisoning is enabled
- *
- * Return true if page poisoning is enabled, or false if not.
- */
-bool page_poisoning_enabled(void)
-{
- /*
- * Assumes that debug_pagealloc_enabled is set before
- * memblock_free_all.
- * Page poisoning is debug page alloc for some arches. If
- * either of those options are enabled, enable poisoning.
- */
- return (static_branch_unlikely(&want_page_poisoning) ||
- (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
- debug_pagealloc_enabled()));
-}
-EXPORT_SYMBOL_GPL(page_poisoning_enabled);
-
static void poison_page(struct page *page)
{
void *addr = kmap_atomic(page);
@@ -127,7 +99,7 @@ static void unpoison_pages(struct page *page, int n)
void kernel_poison_pages(struct page *page, int numpages, int enable)
{
- if (!page_poisoning_enabled())
+ if (!page_poisoning_enabled_static())
return;
if (enable)
--
2.29.0
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