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FROMGIT: mm, page_poison: use static key more efficiently

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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>

(cherry picked from commit 8db26a3d47354ce7271a8cab03cd65b9d3d610b9
 https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm)
Bug: 182930667
Signed-off-by: Alexander Potapenko <glider@google.com>
Change-Id: Ifc3fdf5cd58f3b8346bf81480df3836811e7458b
This commit is contained in:
Vlastimil Babka
2020-12-14 19:13:34 -08:00
committed by Todd Kjos
parent 0879d44ddd
commit e871c7feeb
4 changed files with 52 additions and 54 deletions
Download Patch File Download Diff File Expand all files Collapse all files

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)
{