cgroup: nest kernfs active protection under cgroup_mutex
After the recent cgroup_kn_lock_live() changes, cgroup_mutex is no longer nested below kernfs active protection. The two don't have any relationship now. This patch nests kernfs active protection under cgroup_mutex. All cftype operations now require both cgroup_tree_mutex and cgroup_mutex, temporary cgroup_mutex releases over kernfs operations are removed, and cgroup_add/rm_cftypes() grab both mutexes. This makes cgroup_tree_mutex redundant, which will be removed by the next patch. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
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@ -1127,7 +1127,7 @@ static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn)
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cgrp = kn->parent->priv;
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cgrp = kn->parent->priv;
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/*
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/*
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* We're gonna grab cgroup_tree_mutex which nests outside kernfs
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* We're gonna grab cgroup_mutex which nests outside kernfs
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* active_ref. cgroup liveliness check alone provides enough
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* active_ref. cgroup liveliness check alone provides enough
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* protection against removal. Ensure @cgrp stays accessible and
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* protection against removal. Ensure @cgrp stays accessible and
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* break the active_ref protection.
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* break the active_ref protection.
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@ -1150,6 +1150,7 @@ static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
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char name[CGROUP_FILE_NAME_MAX];
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char name[CGROUP_FILE_NAME_MAX];
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lockdep_assert_held(&cgroup_tree_mutex);
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lockdep_assert_held(&cgroup_tree_mutex);
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lockdep_assert_held(&cgroup_mutex);
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kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
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kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
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}
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}
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@ -1216,11 +1217,9 @@ static int rebind_subsystems(struct cgroup_root *dst_root, unsigned int ss_mask)
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* Nothing can fail from this point on. Remove files for the
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* Nothing can fail from this point on. Remove files for the
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* removed subsystems and rebind each subsystem.
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* removed subsystems and rebind each subsystem.
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*/
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*/
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mutex_unlock(&cgroup_mutex);
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for_each_subsys(ss, ssid)
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for_each_subsys(ss, ssid)
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if (ss_mask & (1 << ssid))
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if (ss_mask & (1 << ssid))
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cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
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cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
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mutex_lock(&cgroup_mutex);
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for_each_subsys(ss, ssid) {
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for_each_subsys(ss, ssid) {
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struct cgroup_root *src_root;
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struct cgroup_root *src_root;
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@ -2946,6 +2945,7 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
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int ret;
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int ret;
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lockdep_assert_held(&cgroup_tree_mutex);
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lockdep_assert_held(&cgroup_tree_mutex);
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lockdep_assert_held(&cgroup_mutex);
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for (cft = cfts; cft->name[0] != '\0'; cft++) {
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for (cft = cfts; cft->name[0] != '\0'; cft++) {
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/* does cft->flags tell us to skip this file on @cgrp? */
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/* does cft->flags tell us to skip this file on @cgrp? */
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@ -2981,6 +2981,7 @@ static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
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int ret = 0;
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int ret = 0;
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lockdep_assert_held(&cgroup_tree_mutex);
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lockdep_assert_held(&cgroup_tree_mutex);
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lockdep_assert_held(&cgroup_mutex);
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/* add/rm files for all cgroups created before */
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/* add/rm files for all cgroups created before */
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css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
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css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
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@ -3049,6 +3050,7 @@ static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
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static int cgroup_rm_cftypes_locked(struct cftype *cfts)
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static int cgroup_rm_cftypes_locked(struct cftype *cfts)
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{
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{
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lockdep_assert_held(&cgroup_tree_mutex);
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lockdep_assert_held(&cgroup_tree_mutex);
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lockdep_assert_held(&cgroup_mutex);
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if (!cfts || !cfts[0].ss)
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if (!cfts || !cfts[0].ss)
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return -ENOENT;
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return -ENOENT;
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@ -3075,7 +3077,9 @@ int cgroup_rm_cftypes(struct cftype *cfts)
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int ret;
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int ret;
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mutex_lock(&cgroup_tree_mutex);
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mutex_lock(&cgroup_tree_mutex);
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mutex_lock(&cgroup_mutex);
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ret = cgroup_rm_cftypes_locked(cfts);
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ret = cgroup_rm_cftypes_locked(cfts);
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mutex_unlock(&cgroup_mutex);
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mutex_unlock(&cgroup_tree_mutex);
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mutex_unlock(&cgroup_tree_mutex);
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return ret;
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return ret;
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}
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}
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@ -3106,12 +3110,14 @@ int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
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return ret;
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return ret;
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mutex_lock(&cgroup_tree_mutex);
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mutex_lock(&cgroup_tree_mutex);
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mutex_lock(&cgroup_mutex);
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list_add_tail(&cfts->node, &ss->cfts);
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list_add_tail(&cfts->node, &ss->cfts);
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ret = cgroup_apply_cftypes(cfts, true);
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ret = cgroup_apply_cftypes(cfts, true);
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if (ret)
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if (ret)
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cgroup_rm_cftypes_locked(cfts);
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cgroup_rm_cftypes_locked(cfts);
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mutex_unlock(&cgroup_mutex);
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mutex_unlock(&cgroup_tree_mutex);
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mutex_unlock(&cgroup_tree_mutex);
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return ret;
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return ret;
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}
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}
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@ -4445,6 +4451,7 @@ static void css_killed_ref_fn(struct percpu_ref *ref)
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static void kill_css(struct cgroup_subsys_state *css)
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static void kill_css(struct cgroup_subsys_state *css)
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{
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{
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lockdep_assert_held(&cgroup_tree_mutex);
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lockdep_assert_held(&cgroup_tree_mutex);
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lockdep_assert_held(&cgroup_mutex);
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/*
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/*
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* This must happen before css is disassociated with its cgroup.
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* This must happen before css is disassociated with its cgroup.
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@ -4544,13 +4551,10 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
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/*
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/*
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* Initiate massacre of all css's. cgroup_destroy_css_killed()
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* Initiate massacre of all css's. cgroup_destroy_css_killed()
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* will be invoked to perform the rest of destruction once the
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* will be invoked to perform the rest of destruction once the
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* percpu refs of all css's are confirmed to be killed. This
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* percpu refs of all css's are confirmed to be killed.
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* involves removing the subsystem's files, drop cgroup_mutex.
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*/
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*/
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mutex_unlock(&cgroup_mutex);
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for_each_css(css, ssid, cgrp)
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for_each_css(css, ssid, cgrp)
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kill_css(css);
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kill_css(css);
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mutex_lock(&cgroup_mutex);
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/* CGRP_DEAD is set, remove from ->release_list for the last time */
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/* CGRP_DEAD is set, remove from ->release_list for the last time */
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raw_spin_lock(&release_list_lock);
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raw_spin_lock(&release_list_lock);
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@ -4567,10 +4571,11 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
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if (!cgrp->nr_css)
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if (!cgrp->nr_css)
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cgroup_destroy_css_killed(cgrp);
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cgroup_destroy_css_killed(cgrp);
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/* remove @cgrp directory along with the base files */
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/*
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mutex_unlock(&cgroup_mutex);
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* Remove @cgrp directory along with the base files. @cgrp has an
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kernfs_remove(cgrp->kn); /* @cgrp has an extra ref on its kn */
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* extra ref on its kn.
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mutex_lock(&cgroup_mutex);
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*/
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kernfs_remove(cgrp->kn);
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return 0;
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return 0;
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};
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};
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