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cgroup: make cgroup hold onto its kernfs_node
cgroup currently releases its kernfs_node when it gets removed. While not buggy, this makes cgroup->kn access rules complicated than necessary and leads to things like get/put protection around kernfs_remove() in cgroup_destroy_locked(). In addition, we want to use kernfs_name/path() and friends but also want to be able to determine a cgroup's name between removal and release. This patch makes cgroup hold onto its kernfs_node until freed so that cgroup->kn is always accessible. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
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parent
21a2d3430b
commit
6f30558f37
1 changed files with 9 additions and 7 deletions
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@ -957,6 +957,8 @@ static void cgroup_free_fn(struct work_struct *work)
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cgroup_pidlist_destroy_all(cgrp);
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kernfs_put(cgrp->kn);
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kfree(rcu_dereference_raw(cgrp->name));
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kfree(cgrp);
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}
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@ -3786,6 +3788,12 @@ static long cgroup_create(struct cgroup *parent, const char *name_str,
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}
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cgrp->kn = kn;
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/*
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* This extra ref will be put in cgroup_free_fn() and guarantees
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* that @cgrp->kn is always accessible.
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*/
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kernfs_get(kn);
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cgrp->serial_nr = cgroup_serial_nr_next++;
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/* allocation complete, commit to creation */
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@ -3966,7 +3974,6 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
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{
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struct cgroup *child;
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struct cgroup_subsys_state *css;
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struct kernfs_node *kn;
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bool empty;
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int ssid;
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@ -4044,13 +4051,8 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
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* clearing of cgrp->kn->priv backpointer, which should happen
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* after all files under it have been removed.
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*/
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kn = cgrp->kn;
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kernfs_get(kn);
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kernfs_remove(cgrp->kn);
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kernfs_remove(cgrp->kn); /* @cgrp has an extra ref on its kn */
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RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL);
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kernfs_put(kn);
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mutex_lock(&cgroup_mutex);
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