From 2a0ff3fbe39bc93f719ff857e5a359d9780579ff Mon Sep 17 00:00:00 2001 From: Jeff Liu Date: Sun, 26 May 2013 21:33:09 +0800 Subject: cgroup: warn about mismatching options of a new mount of an existing hierarchy With the new __DEVEL__sane_behavior mount option was introduced, if the root cgroup is alive with no xattr function, to mount a new cgroup with xattr will be rejected in terms of design which just fine. However, if the root cgroup does not mounted with __DEVEL__sane_hehavior, to create a new cgroup with xattr option will succeed although after that the EA function does not works as expected but will get ENOTSUPP for setting up attributes under either cgroup. e.g. setfattr: /cgroup2/test: Operation not supported Instead of keeping silence in this case, it's better to drop a log entry in warning level. That would be helpful to understand the reason behind the scene from the user's perspective, and this is essentially an improvement does not break the backward compatibilities. With this fix, above mount attemption will keep up works as usual but the following line cound be found at the system log: [ ...] cgroup: new mount options do not match the existing superblock tj: minor formatting / message updates. Signed-off-by: Jie Liu Reported-by: Alexey Kodanev Signed-off-by: Tejun Heo Cc: stable@vger.kernel.org --- kernel/cgroup.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 31e9ef3..a7c9e6d 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1686,11 +1686,14 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, */ cgroup_drop_root(opts.new_root); - if (((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) && - root->flags != opts.flags) { - pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n"); - ret = -EINVAL; - goto drop_new_super; + if (root->flags != opts.flags) { + if ((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) { + pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n"); + ret = -EINVAL; + goto drop_new_super; + } else { + pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n"); + } } /* no subsys rebinding, so refcounts don't change */ -- cgit v1.1