Commit 01f6474c authored by Tejun Heo's avatar Tejun Heo

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent e76ecaee
...@@ -1127,7 +1127,7 @@ static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn) ...@@ -1127,7 +1127,7 @@ static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn)
cgrp = kn->parent->priv; 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 * active_ref. cgroup liveliness check alone provides enough
* protection against removal. Ensure @cgrp stays accessible and * protection against removal. Ensure @cgrp stays accessible and
* break the active_ref protection. * break the active_ref protection.
...@@ -1150,6 +1150,7 @@ static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft) ...@@ -1150,6 +1150,7 @@ static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
char name[CGROUP_FILE_NAME_MAX]; char name[CGROUP_FILE_NAME_MAX];
lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_tree_mutex);
lockdep_assert_held(&cgroup_mutex);
kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name)); 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) ...@@ -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 * Nothing can fail from this point on. Remove files for the
* removed subsystems and rebind each subsystem. * removed subsystems and rebind each subsystem.
*/ */
mutex_unlock(&cgroup_mutex);
for_each_subsys(ss, ssid) for_each_subsys(ss, ssid)
if (ss_mask & (1 << ssid)) if (ss_mask & (1 << ssid))
cgroup_clear_dir(&ss->root->cgrp, 1 << ssid); cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
mutex_lock(&cgroup_mutex);
for_each_subsys(ss, ssid) { for_each_subsys(ss, ssid) {
struct cgroup_root *src_root; struct cgroup_root *src_root;
...@@ -2946,6 +2945,7 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[], ...@@ -2946,6 +2945,7 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
int ret; int ret;
lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_tree_mutex);
lockdep_assert_held(&cgroup_mutex);
for (cft = cfts; cft->name[0] != '\0'; cft++) { for (cft = cfts; cft->name[0] != '\0'; cft++) {
/* does cft->flags tell us to skip this file on @cgrp? */ /* 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) ...@@ -2981,6 +2981,7 @@ static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
int ret = 0; int ret = 0;
lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_tree_mutex);
lockdep_assert_held(&cgroup_mutex);
/* add/rm files for all cgroups created before */ /* add/rm files for all cgroups created before */
css_for_each_descendant_pre(css, cgroup_css(root, ss)) { 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) ...@@ -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) static int cgroup_rm_cftypes_locked(struct cftype *cfts)
{ {
lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_tree_mutex);
lockdep_assert_held(&cgroup_mutex);
if (!cfts || !cfts[0].ss) if (!cfts || !cfts[0].ss)
return -ENOENT; return -ENOENT;
...@@ -3075,7 +3077,9 @@ int cgroup_rm_cftypes(struct cftype *cfts) ...@@ -3075,7 +3077,9 @@ int cgroup_rm_cftypes(struct cftype *cfts)
int ret; int ret;
mutex_lock(&cgroup_tree_mutex); mutex_lock(&cgroup_tree_mutex);
mutex_lock(&cgroup_mutex);
ret = cgroup_rm_cftypes_locked(cfts); ret = cgroup_rm_cftypes_locked(cfts);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgroup_tree_mutex); mutex_unlock(&cgroup_tree_mutex);
return ret; return ret;
} }
...@@ -3106,12 +3110,14 @@ int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) ...@@ -3106,12 +3110,14 @@ int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
return ret; return ret;
mutex_lock(&cgroup_tree_mutex); mutex_lock(&cgroup_tree_mutex);
mutex_lock(&cgroup_mutex);
list_add_tail(&cfts->node, &ss->cfts); list_add_tail(&cfts->node, &ss->cfts);
ret = cgroup_apply_cftypes(cfts, true); ret = cgroup_apply_cftypes(cfts, true);
if (ret) if (ret)
cgroup_rm_cftypes_locked(cfts); cgroup_rm_cftypes_locked(cfts);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgroup_tree_mutex); mutex_unlock(&cgroup_tree_mutex);
return ret; return ret;
} }
...@@ -4445,6 +4451,7 @@ static void css_killed_ref_fn(struct percpu_ref *ref) ...@@ -4445,6 +4451,7 @@ static void css_killed_ref_fn(struct percpu_ref *ref)
static void kill_css(struct cgroup_subsys_state *css) static void kill_css(struct cgroup_subsys_state *css)
{ {
lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_tree_mutex);
lockdep_assert_held(&cgroup_mutex);
/* /*
* This must happen before css is disassociated with its cgroup. * This must happen before css is disassociated with its cgroup.
...@@ -4544,13 +4551,10 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) ...@@ -4544,13 +4551,10 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
/* /*
* Initiate massacre of all css's. cgroup_destroy_css_killed() * Initiate massacre of all css's. cgroup_destroy_css_killed()
* will be invoked to perform the rest of destruction once the * will be invoked to perform the rest of destruction once the
* percpu refs of all css's are confirmed to be killed. This * percpu refs of all css's are confirmed to be killed.
* involves removing the subsystem's files, drop cgroup_mutex.
*/ */
mutex_unlock(&cgroup_mutex);
for_each_css(css, ssid, cgrp) for_each_css(css, ssid, cgrp)
kill_css(css); kill_css(css);
mutex_lock(&cgroup_mutex);
/* CGRP_DEAD is set, remove from ->release_list for the last time */ /* CGRP_DEAD is set, remove from ->release_list for the last time */
raw_spin_lock(&release_list_lock); raw_spin_lock(&release_list_lock);
...@@ -4567,10 +4571,11 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) ...@@ -4567,10 +4571,11 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
if (!cgrp->nr_css) if (!cgrp->nr_css)
cgroup_destroy_css_killed(cgrp); cgroup_destroy_css_killed(cgrp);
/* remove @cgrp directory along with the base files */ /*
mutex_unlock(&cgroup_mutex); * Remove @cgrp directory along with the base files. @cgrp has an
kernfs_remove(cgrp->kn); /* @cgrp has an extra ref on its kn */ * extra ref on its kn.
mutex_lock(&cgroup_mutex); */
kernfs_remove(cgrp->kn);
return 0; return 0;
}; };
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment