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cgroup: Improve cftype add/rm error handling

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Let's track whether a cftype is currently added or not using a new flag
__CFTYPE_ADDED so that duplicate operations can be failed safely and
consistently allow using empty cftypes.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2022-09-06 09:38:42 -10:00
parent a8c52eba88
commit 0083d27b21
2 changed files with 21 additions and 7 deletions
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1
include/linux/cgroup-defs.h
View File

@ -131,6 +131,7 @@ enum {
/* internal flags, do not use outside cgroup core proper */
__CFTYPE_ONLY_ON_DFL = (1 << 16), /* only on default hierarchy */
__CFTYPE_NOT_ON_DFL = (1 << 17), /* not on default hierarchy */
__CFTYPE_ADDED = (1 << 18),
};
/*

27
kernel/cgroup/cgroup.c
View File

@ -4198,19 +4198,26 @@ static void cgroup_exit_cftypes(struct cftype *cfts)
cft->ss = NULL;
/* revert flags set by cgroup core while adding @cfts */
cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL);
cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL |
__CFTYPE_ADDED);
}
}
static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
{
struct cftype *cft;
int ret = 0;
for (cft = cfts; cft->name[0] != '\0'; cft++) {
struct kernfs_ops *kf_ops;
WARN_ON(cft->ss || cft->kf_ops);
if (cft->flags & __CFTYPE_ADDED) {
ret = -EBUSY;
break;
}
if ((cft->flags & CFTYPE_PRESSURE) && !cgroup_psi_enabled())
continue;
@ -4226,26 +4233,26 @@ static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
if (!kf_ops) {
cgroup_exit_cftypes(cfts);
return -ENOMEM;
ret = -ENOMEM;
break;
}
kf_ops->atomic_write_len = cft->max_write_len;
}
cft->kf_ops = kf_ops;
cft->ss = ss;
cft->flags |= __CFTYPE_ADDED;
}
return 0;
if (ret)
cgroup_exit_cftypes(cfts);
return ret;
}
static int cgroup_rm_cftypes_locked(struct cftype *cfts)
{
lockdep_assert_held(&cgroup_mutex);
if (!cfts || !cfts[0].ss)
return -ENOENT;
list_del(&cfts->node);
cgroup_apply_cftypes(cfts, false);
cgroup_exit_cftypes(cfts);
@ -4267,6 +4274,12 @@ int cgroup_rm_cftypes(struct cftype *cfts)
{
int ret;
if (!cfts || cfts[0].name[0] == '\0')
return 0;
if (!(cfts[0].flags & __CFTYPE_ADDED))
return -ENOENT;
mutex_lock(&cgroup_mutex);
ret = cgroup_rm_cftypes_locked(cfts);
mutex_unlock(&cgroup_mutex);