[PATCH] mm/page_poison.c: replace bool variable with static key

[mateusznosek0]

From: Mateusz Nosek <mateusznos...@gmail.com>

Variable 'want_page_poisoning' is a switch deciding if page poisoning
should be enabled. This patch changes it to be static key.

Signed-off-by: Mateusz Nosek <mateusznos...@gmail.com>
---
 mm/page_poison.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/mm/page_poison.c b/mm/page_poison.c
index 34b9181ee5d1..ae0482cded87 100644
--- a/mm/page_poison.c
+++ b/mm/page_poison.c
@@ -8,13 +8,23 @@
 #include <linux/ratelimit.h>
 #include <linux/kasan.h>
 
-static bool want_page_poisoning __read_mostly;
+static DEFINE_STATIC_KEY_FALSE_RO(want_page_poisoning);
 
 static int __init early_page_poison_param(char *buf)
 {
-       if (!buf)
-               return -EINVAL;
-       return strtobool(buf, &want_page_poisoning);
+       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;
 }
 early_param("page_poison", early_page_poison_param);
 
@@ -31,7 +41,7 @@ bool page_poisoning_enabled(void)
         * Page poisoning is debug page alloc for some arches. If
         * either of those options are enabled, enable poisoning.
         */
-       return (want_page_poisoning ||
+       return (static_branch_unlikely(&want_page_poisoning) ||
                (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
                debug_pagealloc_enabled()));
 }
-- 
2.20.1