[Devel] [PATCH VZ8 v2 13/14] cgroup/ve: pass cgroup_root to ve_set(get)_release_agent
Kirill Tkhai
ktkhai at virtuozzo.com
Mon Feb 15 14:08:21 MSK 2021
On 15.02.2021 14:00, Kirill Tkhai wrote:
> On 10.02.2021 13:03, Valeriy Vdovin wrote:
>> Due to virtualization of release_agent cgroup property, cgroup1_show_options
>> has become more complex.
>> struct cgroup_root is one of the arguments to that function, it was previously
>> holding the value of release_agent. But now this property is per-ve AND
>> per-cgroup. That's why to find the right release_agent value, the code should
>> convert cgroup_root into one specific cgroup that is a 'virtual cgroup root' of
>> a container, represented by the current VE. Getting ve is trivial but cgroup
>> can be found by a helper function that will iterate css_set links under
>> cgroup_mutex lock. There is a lock inversion problem when using cgroup_mutex
>> in cgroup1_show_options, lockdep shows cgroup_mutex conflicts with
>> kernfs_node->dep_map.
>> This can be solved easily by converting per-cgroup data structure in VE into
>> per-cgroup-root. This way we can provide ve_set(get)release_agent_path directly
>> with struct cgroup_root agrument. For each cgroup hierarchy there is only one
>> root and for each VE there can only be one virtual root either, that's why
>> it is safe to just use cgroup_root as a key to find the proper release_agent
>> path in each VE.
>>
>> Signed-off-by: Valeriy Vdovin <valeriy.vdovin at virtuozzo.com>
>
> Reviewed-by: Kirill Tkhai <ktkhai at virtuozzo.com>
NACK
>> ---
>> include/linux/ve.h | 8 ++++---
>> kernel/cgroup/cgroup-v1.c | 44 +++++++++++----------------------------
>> kernel/cgroup/cgroup.c | 5 +++--
>> kernel/ve/ve.c | 19 +++++++----------
>> 4 files changed, 27 insertions(+), 49 deletions(-)
>>
>> diff --git a/include/linux/ve.h b/include/linux/ve.h
>> index 7cef4b39847e..3b487f8a4a50 100644
>> --- a/include/linux/ve.h
>> +++ b/include/linux/ve.h
>> @@ -145,12 +145,14 @@ extern int nr_ve;
>> void ve_add_to_release_list(struct cgroup *cgrp);
>> void ve_rm_from_release_list(struct cgroup *cgrp);
>>
>> -int ve_set_release_agent_path(struct cgroup *cgroot,
>> +int ve_set_release_agent_path(struct ve_struct *ve, struct cgroup_root *cgroot,
>> const char *release_agent);
>>
>> -const char *ve_get_release_agent_path(struct cgroup *cgrp_root);
>> +const char *ve_get_release_agent_path(struct ve_struct *ve,
>> + struct cgroup_root *cgroot);
>>
>> -void ve_cleanup_per_cgroot_data(struct ve_struct *ve, struct cgroup *cgrp);
>> +void ve_cleanup_per_cgroot_data(struct ve_struct *ve,
>> + struct cgroup_root *cgrp);
>>
>> extern struct ve_struct *get_ve(struct ve_struct *ve);
>> extern void put_ve(struct ve_struct *ve);
>> diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
>> index 46be2f688503..993ac38b895f 100644
>> --- a/kernel/cgroup/cgroup-v1.c
>> +++ b/kernel/cgroup/cgroup-v1.c
>> @@ -577,7 +577,8 @@ static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
>> }
>>
>> if (root_cgrp->ve_owner)
>> - ret = ve_set_release_agent_path(root_cgrp, strstrip(buf));
>> + ret = ve_set_release_agent_path(root_cgrp->ve_owner,
>> + root_cgrp->root, strstrip(buf));
>> else
>> ret = -ENODEV;
>>
>> @@ -598,7 +599,9 @@ static int cgroup_release_agent_show(struct seq_file *seq, void *v)
>> root_cgrp = cgroup_get_local_root(cgrp);
>> if (root_cgrp->ve_owner) {
>> rcu_read_lock();
>> - release_agent = ve_get_release_agent_path(root_cgrp);
>> + release_agent = ve_get_release_agent_path(
>> + rcu_dereference(root_cgrp->ve_owner),
>> + root_cgrp->root);
>>
>> if (release_agent)
>> seq_puts(seq, release_agent);
>> @@ -910,7 +913,7 @@ void cgroup1_release_agent(struct work_struct *work)
>> goto continue_free;
>> }
>>
>> - release_agent = ve_get_release_agent_path(root_cgrp);
>> + release_agent = ve_get_release_agent_path(ve, root_cgrp->root);
>>
>> *agentbuf = 0;
>> if (release_agent)
>> @@ -931,7 +934,9 @@ void cgroup1_release_agent(struct work_struct *work)
>> envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
>> envp[i] = NULL;
>>
>> +
>> mutex_unlock(&cgroup_mutex);
>> +
>> err = call_usermodehelper_ve(ve, argv[0], argv,
>> envp, UMH_WAIT_EXEC);
>>
>> @@ -939,6 +944,7 @@ void cgroup1_release_agent(struct work_struct *work)
>> pr_warn_ratelimited("cgroup1_release_agent "
>> "%s %s failed: %d\n",
>> agentbuf, pathbuf, err);
>> + up_write(&ve->op_sem);
This must go in other commit.
>> mutex_lock(&cgroup_mutex);
>> continue_free:
>> kfree(pathbuf);
>> @@ -989,7 +995,6 @@ static int cgroup1_show_options(struct seq_file *seq, struct kernfs_root *kf_roo
>> const char *release_agent;
>> struct cgroup_root *root = cgroup_root_from_kf(kf_root);
>> struct cgroup_subsys *ss;
>> - struct cgroup *root_cgrp = &root->cgrp;
>> int ssid;
>>
>> for_each_subsys(ss, ssid)
>> @@ -1003,32 +1008,7 @@ static int cgroup1_show_options(struct seq_file *seq, struct kernfs_root *kf_roo
>> seq_puts(seq, ",cpuset_v2_mode");
>>
>> rcu_read_lock();
>> -#ifdef CONFIG_VE
>> - {
>> - struct ve_struct *ve = get_exec_env();
>> - struct css_set *cset;
>> - struct nsproxy *ve_ns;
>> -
>> - if (!ve_is_super(ve)) {
>> - /*
>> - * ve->init_task is NULL in case when cgroup is accessed
>> - * before ve_start_container has been called.
>> - *
>> - * ve->init_task is synchronized via ve->ve_ns rcu, see
>> - * ve_grab_context/drop_context.
>> - */
>> - ve_ns = rcu_dereference(ve->ve_ns);
>> - if (ve_ns) {
>> - spin_lock_irq(&css_set_lock);
>> - cset = ve_ns->cgroup_ns->root_cset;
>> - BUG_ON(!cset);
>> - root_cgrp = cset_cgroup_from_root(cset, root);
>> - spin_unlock_irq(&css_set_lock);
>> - }
>> - }
>> - }
>> -#endif
>> - release_agent = ve_get_release_agent_path(root_cgrp);
>> + release_agent = ve_get_release_agent_path(get_exec_env(), root);
>> if (release_agent && release_agent[0])
>> seq_show_option(seq, "release_agent", release_agent);
>> rcu_read_unlock();
>> @@ -1226,8 +1206,8 @@ static int cgroup1_remount(struct kernfs_root *kf_root, int *flags, char *data)
>>
>> root_cgrp = cgroup_get_local_root(&root->cgrp);
>> if (root_cgrp->ve_owner)
>> - ret = ve_set_release_agent_path(root_cgrp,
>> - opts.release_agent);
>> + ret = ve_set_release_agent_path(root_cgrp->ve_owner,
>> + root_cgrp->root, opts.release_agent);
>> }
>>
>> trace_cgroup_remount(root);
>> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
>> index 75997b503d3c..09d328b76dab 100644
>> --- a/kernel/cgroup/cgroup.c
>> +++ b/kernel/cgroup/cgroup.c
>> @@ -2152,7 +2152,8 @@ void init_cgroup_root(struct cgroup_root *root, struct cgroup_sb_opts *opts)
>>
>> root->flags = opts->flags;
>> if (opts->release_agent)
>> - ve_set_release_agent_path(cgrp, opts->release_agent);
>> + ve_set_release_agent_path(cgrp->ve_owner, root,
>> + opts->release_agent);
>>
>> if (opts->name)
>> strscpy(root->name, opts->name, MAX_CGROUP_ROOT_NAMELEN);
>> @@ -2360,7 +2361,7 @@ static void cgroup_kill_sb(struct super_block *sb)
>> percpu_ref_kill(&root->cgrp.self.refcnt);
>> cgroup_put(&root->cgrp);
>> kernfs_kill_sb(sb);
>> - ve_cleanup_per_cgroot_data(NULL, &root->cgrp);
>> + ve_cleanup_per_cgroot_data(&ve0, root);
>> }
>>
>> struct file_system_type cgroup_fs_type = {
>> diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
>> index e8945e10e070..031b104075c8 100644
>> --- a/kernel/ve/ve.c
>> +++ b/kernel/ve/ve.c
>> @@ -35,7 +35,7 @@ struct per_cgroot_data {
>> /*
>> * data is related to this cgroup
>> */
>> - struct cgroup *cgroot;
>> + struct cgroup_root *cgroot;
>>
>> /*
>> * path to release agent binaray, that should
>> @@ -217,7 +217,7 @@ int nr_threads_ve(struct ve_struct *ve)
>> EXPORT_SYMBOL(nr_threads_ve);
>>
>> static struct per_cgroot_data *per_cgroot_data_find_locked(
>> - struct list_head *per_cgroot_list, struct cgroup *cgroot)
>> + struct list_head *per_cgroot_list, struct cgroup_root *cgroot)
>> {
>> struct per_cgroot_data *data;
>>
>> @@ -229,7 +229,7 @@ static struct per_cgroot_data *per_cgroot_data_find_locked(
>> }
>>
>> static inline struct per_cgroot_data *per_cgroot_get_or_create(
>> - struct ve_struct *ve, struct cgroup *cgroot)
>> + struct ve_struct *ve, struct cgroup_root *cgroot)
>> {
>> struct per_cgroot_data *data, *other_data;
>> unsigned long flags;
>> @@ -263,10 +263,9 @@ static inline struct per_cgroot_data *per_cgroot_get_or_create(
>> return data;
>> }
>>
>> -int ve_set_release_agent_path(struct cgroup *cgroot,
>> +int ve_set_release_agent_path(struct ve_struct *ve, struct cgroup_root *cgroot,
>> const char *release_agent)
>> {
>> - struct ve_struct *ve;
>> unsigned long flags;
>> struct per_cgroot_data *data;
>> struct cgroup_rcu_string *new_path, *old_path;
>> @@ -276,7 +275,6 @@ int ve_set_release_agent_path(struct cgroup *cgroot,
>> * caller should grab cgroup_mutex to safely use
>> * ve_owner field
>> */
>> - ve = cgroot->ve_owner;
>> BUG_ON(!ve);
>>
>> nbytes = strlen(release_agent);
>> @@ -304,16 +302,15 @@ int ve_set_release_agent_path(struct cgroup *cgroot,
>> return 0;
>> }
>>
>> -const char *ve_get_release_agent_path(struct cgroup *cgroot)
>> +const char *ve_get_release_agent_path(struct ve_struct *ve,
>> + struct cgroup_root *cgroot)
>> {
>> /* caller must grab rcu_read_lock */
>> const char *result = NULL;
>> struct per_cgroot_data *data;
>> struct cgroup_rcu_string *str;
>> - struct ve_struct *ve;
>> unsigned long flags;
>>
>> - ve = rcu_dereference(cgroot->ve_owner);
>> if (!ve)
>> return NULL;
>>
>> @@ -677,15 +674,13 @@ static inline void per_cgroot_data_free(struct per_cgroot_data *data)
>> kfree(data);
>> }
>>
>> -void ve_cleanup_per_cgroot_data(struct ve_struct *ve, struct cgroup *cgrp)
>> +void ve_cleanup_per_cgroot_data(struct ve_struct *ve, struct cgroup_root *cgrp)
>> {
>> struct per_cgroot_data *data, *saved;
>> unsigned long flags;
>>
>> BUG_ON(!ve && !cgrp);
>> rcu_read_lock();
>> - if (!ve)
>> - ve = cgroup_get_ve_owner(cgrp);
>>
>> spin_lock_irqsave(&ve->per_cgroot_list_lock, flags);
>> list_for_each_entry_safe(data, saved, &ve->per_cgroot_list, list) {
>>
>
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