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| author | Tejun Heo <tj@kernel.org> | 2014-05-13 12:19:22 -0400 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2014-05-13 12:19:22 -0400 |
| commit | cfc79d5bec04cdf26cd207d3e73d8bd59fd780a8 (patch) | |
| tree | 96a08e782596ce01a268a9309cf8d3fbc2f18ee9 /kernel/cgroup.c | |
| parent | ddab2b6e0e516098efe6d3b69585bb25b1408d61 (diff) | |
| download | op-kernel-dev-cfc79d5bec04cdf26cd207d3e73d8bd59fd780a8.zip op-kernel-dev-cfc79d5bec04cdf26cd207d3e73d8bd59fd780a8.tar.gz | |
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>
Diffstat (limited to 'kernel/cgroup.c')
| -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 8afddb1..b49e63d 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) |
