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From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        kernel-team@fb.com
Subject: [PATCH] kernel: sysctl: make drop_caches write-only
Date:   Thu, 31 Oct 2019 18:16:02 -0400
Message-Id: <20191031221602.9375-1-hannes@cmpxchg.org>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Currently, the drop_caches proc file and sysctl read back the last
value written, suggesting this is somehow a stateful setting instead
of a one-time command. Make it write-only, like e.g. compact_memory.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 kernel/sysctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 31ece1120aa4..50373984a5e2 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1474,7 +1474,7 @@ static struct ctl_table vm_table[] = {
 		.procname	= "drop_caches",
 		.data		= &sysctl_drop_caches,
 		.maxlen		= sizeof(int),
-		.mode		= 0644,
+		.mode		= 0200,
 		.proc_handler	= drop_caches_sysctl_handler,
 		.extra1		= SYSCTL_ONE,
 		.extra2		= &four,
-- 
2.23.0