[RHEL7,COMMIT] ve/cgroup: set release_agent_path for root cgroups separately for each ve.

Submitted by Vasily Averin on Aug. 6, 2020, 5:32 a.m.

Details

Message ID 202008060532.0765W4pX004102@vz7build.vvs.sw.ru
State New
Series "Make release_agent per-cgroup property. Run release_agent in proper ve."
Headers show

Commit Message

Vasily Averin Aug. 6, 2020, 5:32 a.m.
The commit is pushed to "branch-rh7-3.10.0-1127.18.2.vz7.163.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1127.18.2.el7
------>
commit 87cb5fdb5b5c77ac617b46a0fe118a7d50a77b1c
Author: Valeriy Vdovin <valeriy.vdovin@virtuozzo.com>
Date:   Thu Aug 6 08:32:04 2020 +0300

    ve/cgroup: set release_agent_path for root cgroups separately for each ve.
    
    This is done so that each container could set it's own release agent.
    Release agent information is now stored in per-cgroup-root data
    structure in ve.
    
    https://jira.sw.ru/browse/PSBM-83887
    
    Signed-off-by: Valeriy Vdovin <valeriy.vdovin@virtuozzo.com>
---
 include/linux/cgroup.h |   3 --
 include/linux/ve.h     |   6 +++
 kernel/cgroup.c        | 100 ++++++++++++++++++++++++++++++++++++++++---------
 kernel/ve/ve.c         |  72 +++++++++++++++++++++++++++++++++++
 4 files changed, 161 insertions(+), 20 deletions(-)

Patch hide | download patch | download mbox

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 5f1460d..fc138c0 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -429,9 +429,6 @@  struct cgroupfs_root {
 	/* IDs for cgroups in this hierarchy */
 	struct ida cgroup_ida;
 
-	/* The path to use for release notifications. */
-	char release_agent_path[PATH_MAX];
-
 	/* The name for this hierarchy - may be empty */
 	char name[MAX_CGROUP_ROOT_NAMELEN];
 };
diff --git a/include/linux/ve.h b/include/linux/ve.h
index 65413d5..b6662637 100644
--- a/include/linux/ve.h
+++ b/include/linux/ve.h
@@ -214,6 +214,12 @@  void do_update_load_avg_ve(void);
 
 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 ve_struct *ve, struct cgroup *cgroot,
+	const char *release_agent);
+
+const char *ve_get_release_agent_path(struct cgroup *cgrp_root);
+
 extern struct ve_struct *get_ve(struct ve_struct *ve);
 extern void put_ve(struct ve_struct *ve);
 
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 23bca35..f70bd00 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1095,9 +1095,12 @@  static int rebind_subsystems(struct cgroupfs_root *root,
 
 static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
 {
+	const char *release_agent;
 	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
 	struct cgroup_subsys *ss;
+	struct cgroup *root_cgrp = &root->top_cgroup;
 
+	mutex_lock(&cgroup_mutex);
 	mutex_lock(&cgroup_root_mutex);
 	for_each_subsys(root, ss)
 		seq_printf(seq, ",%s", ss->name);
@@ -1109,14 +1112,37 @@  static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",xattr");
 	if (root->flags & CGRP_ROOT_CPUSET_V2_MODE)
 		seq_puts(seq, ",cpuset_v2_mode");
-	if (strlen(root->release_agent_path))
-		seq_show_option(seq, "release_agent",
-				root->release_agent_path);
+#ifdef CONFIG_VE
+	{
+		struct ve_struct *ve = get_exec_env();
+
+		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.
+			 */
+			rcu_read_lock();
+			if (ve->ve_ns)
+				root_cgrp = task_cgroup_from_root(ve->init_task,
+					root);
+			rcu_read_unlock();
+		}
+	}
+#endif
+	rcu_read_lock();
+	release_agent = ve_get_release_agent_path(root_cgrp);
+	if (release_agent && release_agent[0])
+		seq_show_option(seq, "release_agent", release_agent);
+	rcu_read_unlock();
 	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
 		seq_puts(seq, ",clone_children");
 	if (strlen(root->name))
 		seq_show_option(seq, "name", root->name);
 	mutex_unlock(&cgroup_root_mutex);
+	mutex_unlock(&cgroup_mutex);
 	return 0;
 }
 
@@ -1389,8 +1415,13 @@  static int cgroup_remount(struct super_block *sb, int *flags, char *data)
 	/* re-populate subsystem files */
 	cgroup_populate_dir(cgrp, false, added_mask);
 
-	if (opts.release_agent)
-		strcpy(root->release_agent_path, opts.release_agent);
+	if (opts.release_agent) {
+		struct cgroup *root_cgrp;
+		root_cgrp = cgroup_get_local_root(cgrp);
+		if (root_cgrp->ve_owner)
+			ret = ve_set_release_agent_path(root_cgrp,
+				opts.release_agent);
+	}
  out_unlock:
 	kfree(opts.release_agent);
 	kfree(opts.name);
@@ -1714,8 +1745,6 @@  static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
 	root->subsys_mask = opts->subsys_mask;
 	root->flags = opts->flags;
 	ida_init(&root->cgroup_ida);
-	if (opts->release_agent)
-		strcpy(root->release_agent_path, opts->release_agent);
 	if (opts->name)
 		strcpy(root->name, opts->name);
 	if (opts->cpuset_clone_children)
@@ -1914,6 +1943,11 @@  static struct dentry *cgroup_mount(struct file_system_type *fs_type,
 
 		cred = override_creds(&init_cred);
 		cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
+		if (opts.release_agent) {
+			ret = ve_set_release_agent_path(root_cgrp,
+				opts.release_agent);
+		}
+
 		revert_creds(cred);
 		mutex_unlock(&cgroup_root_mutex);
 		mutex_unlock(&cgroup_mutex);
@@ -2483,7 +2517,8 @@  static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
 static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
 				      const char *buffer)
 {
-	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
+	int ret = 0;
+	struct cgroup *root_cgrp;
 
 	if (strlen(buffer) >= PATH_MAX)
 		return -EINVAL;
@@ -2491,19 +2526,35 @@  static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
 	if (!cgroup_lock_live_group(cgrp))
 		return -ENODEV;
 
-	mutex_lock(&cgroup_root_mutex);
-	strcpy(cgrp->root->release_agent_path, buffer);
-	mutex_unlock(&cgroup_root_mutex);
+	root_cgrp = cgroup_get_local_root(cgrp);
+	BUG_ON(!root_cgrp);
+	if (root_cgrp->ve_owner)
+		ret = ve_set_release_agent_path(root_cgrp, buffer);
+	else
+		ret = -ENODEV;
+
 	mutex_unlock(&cgroup_mutex);
-	return 0;
+	return ret;
 }
 
 static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
 				     struct seq_file *seq)
 {
+	const char *release_agent;
+	struct cgroup *root_cgrp;
+
 	if (!cgroup_lock_live_group(cgrp))
 		return -ENODEV;
-	seq_puts(seq, cgrp->root->release_agent_path);
+
+	root_cgrp = cgroup_get_local_root(cgrp);
+	if (root_cgrp->ve_owner) {
+		rcu_read_lock();
+		release_agent = ve_get_release_agent_path(root_cgrp);
+
+		if (release_agent)
+			seq_puts(seq, release_agent);
+		rcu_read_unlock();
+	}
 	seq_putc(seq, '\n');
 	mutex_unlock(&cgroup_mutex);
 	return 0;
@@ -5698,15 +5749,24 @@  static void check_for_release(struct cgroup *cgrp)
 void cgroup_release_agent(struct work_struct *work)
 {
 	struct ve_struct *ve;
+	char *agentbuf;
+
+	agentbuf = kzalloc(PATH_MAX, GFP_KERNEL);
+	if (!agentbuf) {
+		pr_warn("failed to allocate agentbuf\n");
+		return;
+	}
+
 	ve = container_of(work, struct ve_struct, release_agent_work);
 	mutex_lock(&cgroup_mutex);
 	raw_spin_lock(&ve->release_list_lock);
 	while (!list_empty(&ve->release_list)) {
 		char *argv[3], *envp[3];
 		int i, err;
-		char *pathbuf = NULL, *agentbuf = NULL;
+		char *pathbuf = NULL;
 		struct cgroup *cgrp, *root_cgrp;
 		struct task_struct *ve_task;
+		const char *release_agent;
 
 		cgrp = list_entry(ve->release_list.next,
 				  struct cgroup,
@@ -5734,9 +5794,15 @@  void cgroup_release_agent(struct work_struct *work)
 			rcu_read_unlock();
 			goto continue_free;
 		}
+
+		release_agent = ve_get_release_agent_path(root_cgrp);
+
+		*agentbuf = 0;
+		if (release_agent)
+			strncpy(agentbuf, release_agent, PATH_MAX);
 		rcu_read_unlock();
-		agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
-		if (!agentbuf)
+
+		if (!*agentbuf)
 			goto continue_free;
 
 		i = 0;
@@ -5767,11 +5833,11 @@  void cgroup_release_agent(struct work_struct *work)
 		mutex_lock(&cgroup_mutex);
  continue_free:
 		kfree(pathbuf);
-		kfree(agentbuf);
 		raw_spin_lock(&ve->release_list_lock);
 	}
 	raw_spin_unlock(&ve->release_list_lock);
 	mutex_unlock(&cgroup_mutex);
+	kfree(agentbuf);
 }
 
 static int __init cgroup_disable(char *str)
diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
index f564dca..f03f665 100644
--- a/kernel/ve/ve.c
+++ b/kernel/ve/ve.c
@@ -51,6 +51,11 @@  struct per_cgroot_data {
 	 * data is related to this cgroup
 	 */
 	struct cgroup *cgroot;
+	/*
+	 * path to release agent binaray, that should
+	 * be spawned for all cgroups under this cgroup root
+	 */
+	struct cgroup_rcu_string __rcu *release_agent_path;
 };
 
 extern struct kmapset_set sysfs_ve_perms_set;
@@ -175,6 +180,68 @@  static inline struct per_cgroot_data *per_cgroot_get_or_create(
 	return data;
 }
 
+int ve_set_release_agent_path(struct cgroup *cgroot,
+	const char *release_agent)
+{
+	struct ve_struct *ve;
+	struct per_cgroot_data *data;
+	struct cgroup_rcu_string *new_path, *old_path;
+	int err = 0;
+
+	/*
+	 * caller should grab cgroup_mutex to safely use
+	 * ve_owner field
+	 */
+	ve = cgroot->ve_owner;
+	BUG_ON(!ve);
+
+	new_path = cgroup_rcu_strdup(release_agent, strlen(release_agent));
+	if (IS_ERR(new_path))
+		return PTR_ERR(new_path);
+
+	data = per_cgroot_get_or_create(ve, cgroot);
+	if (IS_ERR(data)) {
+		kfree(new_path);
+		return PTR_ERR(data);
+	}
+
+	raw_spin_lock(&ve->per_cgroot_list_lock);
+
+	old_path = rcu_dereference_protected(data->release_agent_path,
+		lockdep_is_held(&ve->per_cgroot_list_lock));
+
+	rcu_assign_pointer(data->release_agent_path, new_path);
+	raw_spin_unlock(&ve->per_cgroot_list_lock);
+
+	if (old_path)
+		kfree_rcu(old_path, rcu_head);
+
+	return err;
+}
+
+const char *ve_get_release_agent_path(struct cgroup *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;
+	ve = rcu_dereference(cgroot->ve_owner);
+	if (!ve)
+		return NULL;
+
+	raw_spin_lock(&ve->per_cgroot_list_lock);
+
+	data = per_cgroot_data_find_locked(&ve->per_cgroot_list, cgroot);
+	if (data) {
+		str = rcu_dereference(data->release_agent_path);
+		if (str)
+			result = str->val;
+	}
+	raw_spin_unlock(&ve->per_cgroot_list_lock);
+	return result;
+}
+
 struct cgroup_subsys_state *ve_get_init_css(struct ve_struct *ve, int subsys_id)
 {
 	struct cgroup_subsys_state *css, *tmp;
@@ -677,9 +744,14 @@  err_list:
 static void ve_per_cgroot_free(struct ve_struct *ve)
 {
 	struct per_cgroot_data *data, *saved;
+	struct cgroup_rcu_string *release_agent;
 
 	raw_spin_lock(&ve->per_cgroot_list_lock);
 	list_for_each_entry_safe(data, saved, &ve->per_cgroot_list, list) {
+		release_agent = data->release_agent_path;
+		RCU_INIT_POINTER(data->release_agent_path, NULL);
+		if (release_agent)
+			kfree_rcu(release_agent, rcu_head);
 		list_del_init(&data->list);
 		kfree(data);
 	}