[PATCH] Make /proc/sys/vm/drop_caches write only

[Nikanth Karthikesan]

 /proc/sys/vm/drop_caches is used only to trigger dropping caches. It does not 
disable the cache. The ability to read the value written to this file long 
back gives wrong impression.

Signed-off-by: Nikanth Karthikesan <knikanth@xxxxxxx>

---

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index 3e5637f..9892e1b 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -66,11 +66,9 @@ int drop_caches_sysctl_handler(ctl_table *table, int write,
 	struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
 {
 	proc_dointvec_minmax(table, write, file, buffer, length, ppos);
-	if (write) {
-		if (sysctl_drop_caches & 1)
-			drop_pagecache();
-		if (sysctl_drop_caches & 2)
-			drop_slab();
-	}
+	if (sysctl_drop_caches & 1)
+		drop_pagecache();
+	if (sysctl_drop_caches & 2)
+		drop_slab();
 	return 0;
 }
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 9d048fa..dff3c13 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1015,7 +1015,7 @@ 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,
 		.strategy	= &sysctl_intvec,
 	},

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