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cgroup: CGRP_ROOT_SUBSYS_BOUND should be ignored when comparing mount options

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1672d04070 ("cgroup: fix cgroupfs_root early destruction path")
introduced CGRP_ROOT_SUBSYS_BOUND which is used to mark completion of
subsys binding on a new root; however, this broke remounts.
cgroup_remount() doesn't allow changing root options via remount and
CGRP_ROOT_SUBSYS_BOUND, which is set on all fully initialized roots,
makes the function reject all remounts.

Fix it by putting the options part in the lower 16 bits of root->flags
and masking the comparions.  While at it, make cgroup_remount() emit
an error message explaining why it's rejecting a remount request, so
that it's less of a mystery.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2013-06-27 19:37:26 -07:00
parent e2bd416f62
commit 0ce6cba357
2 changed files with 9 additions and 2 deletions
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6
include/linux/cgroup.h
View file

@ -276,7 +276,11 @@ enum {
CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
CGRP_ROOT_SUBSYS_BOUND = (1 << 3), /* subsystems finished binding */
/* mount options live below bit 16 */
CGRP_ROOT_OPTION_MASK = (1 << 16) - 1,
CGRP_ROOT_SUBSYS_BOUND = (1 << 16), /* subsystems finished binding */
};
/*

5
kernel/cgroup.c
View file

@ -1362,8 +1362,11 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
removed_mask = root->subsys_mask & ~opts.subsys_mask;
/* Don't allow flags or name to change at remount */
if (opts.flags != root->flags ||
if (((opts.flags ^ root->flags) & CGRP_ROOT_OPTION_MASK) ||
(opts.name && strcmp(opts.name, root->name))) {
pr_err("cgroup: option or name mismatch, new: 0x%lx \"%s\", old: 0x%lx \"%s\"\n",
opts.flags & CGRP_ROOT_OPTION_MASK, opts.name ?: "",
root->flags & CGRP_ROOT_OPTION_MASK, root->name);
ret = -EINVAL;
goto out_unlock;
}