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cgroup: nest kernfs active protection under cgroup_mutex

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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>
This commit is contained in:
Tejun Heo 2014-05-13 12:19:23 -04:00
parent e76ecaeef6
commit 01f6474ce0
1 changed files with 16 additions and 11 deletions
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27
kernel/cgroup.c
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@ -1127,7 +1127,7 @@ static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn)
cgrp = kn->parent->priv;
/*
* We're gonna grab cgroup_tree_mutex which nests outside kernfs
* We're gonna grab cgroup_mutex which nests outside kernfs
* active_ref. cgroup liveliness check alone provides enough
* protection against removal. Ensure @cgrp stays accessible and
* break the active_ref protection.
@ -1150,6 +1150,7 @@ static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
char name[CGROUP_FILE_NAME_MAX];
lockdep_assert_held(&cgroup_tree_mutex);
lockdep_assert_held(&cgroup_mutex);
kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
}
@ -1216,11 +1217,9 @@ static int rebind_subsystems(struct cgroup_root *dst_root, unsigned int ss_mask)
* Nothing can fail from this point on. Remove files for the
* removed subsystems and rebind each subsystem.
*/
mutex_unlock(&cgroup_mutex);
for_each_subsys(ss, ssid)
if (ss_mask & (1 << ssid))
cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
mutex_lock(&cgroup_mutex);
for_each_subsys(ss, ssid) {
struct cgroup_root *src_root;
@ -2946,6 +2945,7 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
int ret;
lockdep_assert_held(&cgroup_tree_mutex);
lockdep_assert_held(&cgroup_mutex);
for (cft = cfts; cft->name[0] != '\0'; cft++) {
/* does cft->flags tell us to skip this file on @cgrp? */
@ -2981,6 +2981,7 @@ static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
int ret = 0;
lockdep_assert_held(&cgroup_tree_mutex);
lockdep_assert_held(&cgroup_mutex);
/* add/rm files for all cgroups created before */
css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
@ -3049,6 +3050,7 @@ static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
static int cgroup_rm_cftypes_locked(struct cftype *cfts)
{
lockdep_assert_held(&cgroup_tree_mutex);
lockdep_assert_held(&cgroup_mutex);
if (!cfts || !cfts[0].ss)
return -ENOENT;
@ -3075,7 +3077,9 @@ int cgroup_rm_cftypes(struct cftype *cfts)
int ret;
mutex_lock(&cgroup_tree_mutex);
mutex_lock(&cgroup_mutex);
ret = cgroup_rm_cftypes_locked(cfts);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgroup_tree_mutex);
return ret;
}
@ -3106,12 +3110,14 @@ int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
return ret;
mutex_lock(&cgroup_tree_mutex);
mutex_lock(&cgroup_mutex);
list_add_tail(&cfts->node, &ss->cfts);
ret = cgroup_apply_cftypes(cfts, true);
if (ret)
cgroup_rm_cftypes_locked(cfts);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgroup_tree_mutex);
return ret;
}
@ -4445,6 +4451,7 @@ static void css_killed_ref_fn(struct percpu_ref *ref)
static void kill_css(struct cgroup_subsys_state *css)
{
lockdep_assert_held(&cgroup_tree_mutex);
lockdep_assert_held(&cgroup_mutex);
/*
* This must happen before css is disassociated with its cgroup.
@ -4544,13 +4551,10 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
/*
* Initiate massacre of all css's. cgroup_destroy_css_killed()
* will be invoked to perform the rest of destruction once the
* percpu refs of all css's are confirmed to be killed. This
* involves removing the subsystem's files, drop cgroup_mutex.
* percpu refs of all css's are confirmed to be killed.
*/
mutex_unlock(&cgroup_mutex);
for_each_css(css, ssid, cgrp)
kill_css(css);
mutex_lock(&cgroup_mutex);
/* CGRP_DEAD is set, remove from ->release_list for the last time */
raw_spin_lock(&release_list_lock);
@ -4567,10 +4571,11 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
if (!cgrp->nr_css)
cgroup_destroy_css_killed(cgrp);
/* remove @cgrp directory along with the base files */
mutex_unlock(&cgroup_mutex);
kernfs_remove(cgrp->kn); /* @cgrp has an extra ref on its kn */
mutex_lock(&cgroup_mutex);
/*
* Remove @cgrp directory along with the base files. @cgrp has an
* extra ref on its kn.
*/
kernfs_remove(cgrp->kn);
return 0;
};