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cgroups: don't change release_agent when remount failed 

Remount can fail in either case:
  - wrong mount options is specified, or option 'noprefix' is changed.
  - a to-be-added subsys is already mounted/active.

When using remount to change 'release_agent', for the above former failure
case, remount will return errno with release_agent unchanged, but for the
latter case, remount will return EBUSY with relase_agent changed, which is
unexpected I think:

 # mount -t cgroup -o cpu xxx /cgrp1
 # mount -t cgroup -o cpuset,release_agent=agent1 yyy /cgrp2
 # cat /cgrp2/release_agent
 agent1
 # mount -t cgroup -o remount,cpuset,noprefix,release_agent=agent2 yyy /cgrp2
 mount: /cgrp2 not mounted already, or bad option
 # cat /cgrp2/release_agent
 agent1     <-- ok
 # mount -t cgroup -o remount,cpu,cpuset,release_agent=agent2 yyy /cgrp2
 mount: /cgrp2 is busy
 # cat /cgrp2/release_agent
 agent2     <-- unexpected!

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Li Zefan 2009-04-02 16:57:30 -07:00 committed by Linus Torvalds
parent 099fca3225
commit 0670e08bdf
1 changed files with 3 additions and 2 deletions
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5
kernel/cgroup.c
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@ -915,10 +915,11 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
}
ret = rebind_subsystems(root, opts.subsys_bits);
if (ret)
goto out_unlock;
/* (re)populate subsystem files */
if (!ret)
cgroup_populate_dir(cgrp);
cgroup_populate_dir(cgrp);
if (opts.release_agent)
strcpy(root->release_agent_path, opts.release_agent);