From a73456f37b9dbc917398387d0cba926b4455b70f Mon Sep 17 00:00:00 2001
From: Li Zefan <lizefan@huawei.com>
Date: Wed, 5 Jun 2013 17:15:59 +0800
Subject: cpuset: re-structure update_cpumask() a bit

Check if cpus_allowed is to be changed before calling validate_change().

This won't change any behavior, but later it will allow us to do this:

 # mkdir /cpuset/child
 # echo $$ > /cpuset/child/tasks	/* empty cpuset */
 # echo > /cpuset/child/cpuset.cpus	/* do nothing, won't fail */

Without this patch, the last operation will fail.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/cpuset.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

(limited to 'kernel')

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 51f8e1d5a2a9..535dce685eec 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -856,14 +856,15 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
 		if (!cpumask_subset(trialcs->cpus_allowed, cpu_active_mask))
 			return -EINVAL;
 	}
-	retval = validate_change(cs, trialcs);
-	if (retval < 0)
-		return retval;
 
 	/* Nothing to do if the cpus didn't change */
 	if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
 		return 0;
 
+	retval = validate_change(cs, trialcs);
+	if (retval < 0)
+		return retval;
+
 	retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);
 	if (retval)
 		return retval;
-- 
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