[Devel] Re: Question for remount

[Li Zefan]

Li Zefan wrote:
>> 1. Documentation/cgroups/cgroup.txt says
>>    #mount -oremount,cpuset,ns /dev/cgroup
>>    But this should be
>>    #mount -tcgroup none /dev/cgroup -oremount,cpuset,ns
>>
> 
> I agree. Actually I noticed this long ago.
> 
> Doing this won't remove cpuacct from the cgroup hierarchy:
> # mount -t cgroup -o cpu,cpuacct xxx /mnt
> # mount -o remount,cpu /mnt
> This will get you right:
> # mount [-t cgroup] -o remount,cpu xxx /mnt
> 

How about this patch:

[PATCH] cgroups: fix documentation about remount

This won't remove cpuacct from the mounted hierachy:
 # mount -t cgroup -o cpu,cpuacct xxx /mnt
 # mount -o remount,cpu /mnt

Because for this usage mount(8) will append the new options to the current
options.

And this will get you right:
 # mount [-t cgroup] -o remount,cpu xxx /mnt

Signed-off-by: Li Zefan <lizf at cn.fujitsu.com>
---
 Documentation/cgroups/cgroups.txt |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index 93feb84..5cbeab2 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -337,8 +337,13 @@ subsystems, type:
 
 To change the set of subsystems bound to a mounted hierarchy, just
 remount with different options:
+# mount -o remount,cpuset,ns hier1 /dev/cgroup
 
-# mount -o remount,cpuset,ns  /dev/cgroup
+Now numtasks is removed from the hierarchy and ns is added.
+
+Note this will add ns to the hierarchy but won't remove numtasks or
+cpuset:
+# mount -o remount,ns /dev/cgroup
 
 Note that changing the set of subsystems is currently only supported
 when the hierarchy consists of a single (root) cgroup. Supporting
-- 
1.5.4.rc3

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