From 0083d27b21dd2a598df8275b98f89ced532e2e53 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 6 Sep 2022 09:38:42 -1000 Subject: [PATCH] cgroup: Improve cftype add/rm error handling 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 --- include/linux/cgroup-defs.h | 1 + kernel/cgroup/cgroup.c | 27 ++++++++++++++++++++------- 2 files changed, 21 insertions(+), 7 deletions(-) diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 1283993d7ea8..9fa1652d0493 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -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), }; /* diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index e0b72eb5d283..bd9fe6e88320 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -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);