linux-kernel - [PATCH] drop_caches: re-enable message after disabling

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Message-Id: <20250216100514.3948-1-rwchen404@gmail.com>
Date: Sun, 16 Feb 2025 18:05:14 +0800
From: Ruiwu Chen <rwchen404@...il.com>
To: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: viro@...iv.linux.org.uk,
	brauner@...nel.org,
	jack@...e.cz,
	kees@...nel.org,
	joel.granados@...nel.org,
	Ruiwu Chen <rwchen404@...il.com>
Subject: [PATCH] drop_caches: re-enable message after disabling

When 'echo 4 > /proc/sys/vm/drop_caches' the message is disabled,
but there is no interface to enable the message, only by restarting
the way, so I want to add the 'echo 0 > /proc/sys/vm/drop_caches'
way to enabled the message again.

Signed-off-by: Ruiwu Chen <rwchen404@...il.com>
---
 fs/drop_caches.c | 7 +++++--
 kernel/sysctl.c  | 2 +-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index d45ef541d848..c90cfaf9756d 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -57,7 +57,7 @@ int drop_caches_sysctl_handler(const struct ctl_table *table, int write,
 	if (ret)
 		return ret;
 	if (write) {
-		static int stfu;
+		static bool stfu;
 
 		if (sysctl_drop_caches & 1) {
 			lru_add_drain_all();
@@ -73,7 +73,10 @@ int drop_caches_sysctl_handler(const struct ctl_table *table, int write,
 				current->comm, task_pid_nr(current),
 				sysctl_drop_caches);
 		}
-		stfu |= sysctl_drop_caches & 4;
+		if (sysctl_drop_caches == 0)
+			stfu = false;
+		else if (sysctl_drop_caches == 4)
+			stfu = true;
 	}
 	return 0;
 }
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index cb57da499ebb..f2e06e074724 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2088,7 +2088,7 @@ static const struct ctl_table vm_table[] = {
 		.maxlen		= sizeof(int),
 		.mode		= 0200,
 		.proc_handler	= drop_caches_sysctl_handler,
-		.extra1		= SYSCTL_ONE,
+		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_FOUR,
 	},
 	{
-- 
2.27.0