Commit 0670e08b authored Apr 02, 2009 by Li Zefan Committed by Linus Torvalds Apr 02, 2009

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>

parent 099fca32

kernel/cgroup.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -915,9 +915,10 @@ 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);

		if (opts.release_agent)