diff options
| author | Tejun Heo <tj@kernel.org> | 2014-05-13 18:19:22 +0200 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2014-05-13 18:19:22 +0200 |
| commit | cfc79d5bec04cdf26cd207d3e73d8bd59fd780a8 (patch) | |
| tree | 96a08e782596ce01a268a9309cf8d3fbc2f18ee9 | |
| parent | cgroup: grab cgroup_mutex earlier in cgroup_subtree_control_write() (diff) | |
| download | linux-cfc79d5bec04cdf26cd207d3e73d8bd59fd780a8.tar.xz linux-cfc79d5bec04cdf26cd207d3e73d8bd59fd780a8.zip | |
cgroup: move cgroup->kn->priv clearing to cgroup_rmdir()
The ->priv field of a cgroup directory kernfs_node points back to the
cgroup. This field is RCU cleared in cgroup_destroy_locked() for
non-kernfs accesses from css_tryget_from_dir() and
cgroupstats_build().
As these are only applicable to cgroups which finished creation
successfully and fully initialized cgroups are always removed by
cgroup_rmdir(), this can be safely moved to the end of cgroup_rmdir().
This will help simplifying cgroup locking and shouldn't introduce any
behavior difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
| -rw-r--r-- | kernel/cgroup.c | 23 |
1 files changed, 12 insertions, 11 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 8afddb1a1c6c..b49e63d5386b 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4546,17 +4546,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) /* remove @cgrp directory along with the base files */ mutex_unlock(&cgroup_mutex); - - /* - * There are two control paths which try to determine cgroup from - * dentry without going through kernfs - cgroupstats_build() and - * css_tryget_online_from_dir(). Those are supported by RCU - * protecting clearing of cgrp->kn->priv backpointer, which should - * happen after all files under it have been removed. - */ kernfs_remove(cgrp->kn); /* @cgrp has an extra ref on its kn */ - RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL); - mutex_lock(&cgroup_mutex); return 0; @@ -4615,6 +4605,17 @@ static int cgroup_rmdir(struct kernfs_node *kn) mutex_unlock(&cgroup_tree_mutex); kernfs_unbreak_active_protection(kn); + + /* + * There are two control paths which try to determine cgroup from + * dentry without going through kernfs - cgroupstats_build() and + * css_tryget_online_from_dir(). Those are supported by RCU + * protecting clearing of cgrp->kn->priv backpointer, which should + * happen after all files under it have been removed. + */ + if (!ret) + RCU_INIT_POINTER(*(void __rcu __force **)&kn->priv, NULL); + cgroup_put(cgrp); return ret; } @@ -5174,7 +5175,7 @@ struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, /* * This path doesn't originate from kernfs and @kn could already * have been or be removed at any point. @kn->priv is RCU - * protected for this access. See destroy_locked() for details. + * protected for this access. See cgroup_rmdir() for details. */ cgrp = rcu_dereference(kn->priv); if (cgrp) |