Re: [PATCH] cgroups: forbid noprefix if mounting more than just cpuset subsystem

[Li Zefan <lizf@cn.fujitsu.com>]

>> +	/* We allow noprefix only if mounting just the cpuset subsystem */
>> +	if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
>> +	    (opts->subsys_bits & mask))
>> +		return -EINVAL;
>> +
> 
> uh, OK.  I hope that comment is clear enough for anyone who wants to
> understand it.   It doesn't explain _why_ this is done..
> 

I agree more explanation is better..

====

From: Li Zefan <lizf@cn.fujitsu.com>
Subject: [PATCH] cgroups: forbid noprefix if mounting more than just cpuset subsystem, fix2

Explain more on the noprefix option.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 kernel/cgroup.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index ad17f9d..d15432c 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -891,7 +891,11 @@ static int parse_cgroupfs_options(char *data,
 		}
 	}
 
-	/* We allow noprefix only if mounting just the cpuset subsystem */
+	/*
+	 * Option noprefix was introduced just for backward compatibility
+	 * with the old cpuset, so we allow noprefix only if mounting just
+	 * the cpuset subsystem.
+	 */
 	if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
 	    (opts->subsys_bits & mask))
 		return -EINVAL;
-- 
1.5.4.rc3