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mm, page_poison: use static key more efficiently 

Commit 11c9c7edae ("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.

The function kernel_poison_pages() is also called unconditionally and does
the static key check inside.  Remove it from there and put it to callers.
Also split it to two functions kernel_poison_pages() and
kernel_unpoison_pages() instead of the confusing bool parameter.

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_and_hardening() to enable a single
static key instead of having two static branches in
page_poisoning_enabled_static().

Link: https://lkml.kernel.org/r/20201113104033.22907-3-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Laura Abbott <labbott@kernel.org>
Cc: Mateusz Nosek <mateusznosek0@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vlastimil Babka 2020-12-14 19:13:34 -08:00 committed by Linus Torvalds
parent 04013513cc
commit 8db26a3d47
4 changed files with 52 additions and 54 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/virtio/virtio_balloon.c
View File

@ -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);

33
include/linux/mm.h
View File

@ -2874,12 +2874,37 @@ extern int apply_to_existing_page_range(struct mm_struct *mm,
extern void init_mem_debugging_and_hardening(void);
#ifdef CONFIG_PAGE_POISONING
extern bool page_poisoning_enabled(void);
extern void kernel_poison_pages(struct page *page, int numpages, int enable);
extern void __kernel_poison_pages(struct page *page, int numpages);
extern void __kernel_unpoison_pages(struct page *page, int numpages);
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);
}
static inline void kernel_poison_pages(struct page *page, int numpages)
{
if (page_poisoning_enabled_static())
__kernel_poison_pages(page, numpages);
}
static inline void kernel_unpoison_pages(struct page *page, int numpages)
{
if (page_poisoning_enabled_static())
__kernel_unpoison_pages(page, numpages);
}
#else
static inline bool page_poisoning_enabled(void) { return false; }
static inline void kernel_poison_pages(struct page *page, int numpages,
int enable) { }
static inline bool page_poisoning_enabled_static(void) { return false; }
static inline void kernel_poison_pages(struct page *page, int numpages) { }
static inline void kernel_unpoison_pages(struct page *page, int numpages) { }
#endif
DECLARE_STATIC_KEY_FALSE(init_on_alloc);

18
mm/page_alloc.c
View File

@ -777,6 +777,17 @@ void init_mem_debugging_and_hardening(void)
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;
@ -1262,7 +1273,8 @@ static __always_inline bool free_pages_prepare(struct page *page,
if (want_init_on_free())
kernel_init_free_pages(page, 1 << order);
kernel_poison_pages(page, 1 << order, 0);
kernel_poison_pages(page, 1 << order);
/*
* arch_free_page() can make the page's contents inaccessible. s390
* does this. So nothing which can access the page's contents should
@ -2219,7 +2231,7 @@ 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
@ -2281,7 +2293,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
arch_alloc_page(page, order);
debug_pagealloc_map_pages(page, 1 << order);
kasan_alloc_pages(page, order);
kernel_poison_pages(page, 1 << order, 1);
kernel_unpoison_pages(page, 1 << order);
set_page_owner(page, order, gfp_flags);
if (!free_pages_prezeroed() && want_init_on_alloc(gfp_flags))

53
mm/page_poison.c
View File

@ -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(_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);
@ -58,7 +30,7 @@ static void poison_page(struct page *page)
kunmap_atomic(addr);
}
static void poison_pages(struct page *page, int n)
void __kernel_poison_pages(struct page *page, int n)
{
int i;
@ -117,7 +89,7 @@ static void unpoison_page(struct page *page)
kunmap_atomic(addr);
}
static void unpoison_pages(struct page *page, int n)
void __kernel_unpoison_pages(struct page *page, int n)
{
int i;
@ -125,17 +97,6 @@ static void unpoison_pages(struct page *page, int n)
unpoison_page(page + i);
}
void kernel_poison_pages(struct page *page, int numpages, int enable)
{
if (!page_poisoning_enabled())
return;
if (enable)
unpoison_pages(page, numpages);
else
poison_pages(page, numpages);
}
#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
void __kernel_map_pages(struct page *page, int numpages, int enable)
{