[Devel] [patch rh7 3/3] cgroups: Drop per-cgroup release_agent code

[Cyrill Gorcunov]

It was introduced for cgroups virtualization but since we
use bindmounts, lets drop it and step back to native
per-root @release_agent_path.

Signed-off-by: Cyrill Gorcunov <gorcunov at odin.com>
CC: Vladimir Davydov <vdavydov at odin.com>
CC: Konstantin Khorenko <khorenko at odin.com>
CC: Pavel Emelyanov <xemul at odin.com>
CC: Andrey Vagin <avagin at odin.com>
---
 include/linux/cgroup.h |    6 +++---
 kernel/cgroup.c        |   42 +++++++++++-------------------------------
 2 files changed, 14 insertions(+), 34 deletions(-)

Index: linux-pcs7.git/include/linux/cgroup.h
===================================================================
--- linux-pcs7.git.orig/include/linux/cgroup.h
+++ linux-pcs7.git/include/linux/cgroup.h
@@ -236,9 +236,6 @@ struct cgroup {
 
 	struct cgroupfs_root *root;
 
-	/* The path to use for release notifications. */
-	char *release_agent;
-
 	/* Owner VE for fake cgroup hierarchy */
 	struct ve_struct *cgroup_ve;
 	struct list_head cgroup_ve_list;
@@ -364,6 +361,9 @@ 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];
 };
Index: linux-pcs7.git/kernel/cgroup.c
===================================================================
--- linux-pcs7.git.orig/kernel/cgroup.c
+++ linux-pcs7.git/kernel/cgroup.c
@@ -852,7 +852,6 @@ static void cgroup_free_fn(struct work_s
 		ss->css_free(cgrp);
 
 	cgrp->root->number_of_cgroups--;
-	kfree(cgrp->release_agent);
 	mutex_unlock(&cgroup_mutex);
 
 	/*
@@ -1093,7 +1092,6 @@ static int rebind_subsystems(struct cgro
 static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
 {
 	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
-	struct cgroup *top_cgrp;
 	struct cgroup_subsys *ss;
 
 	mutex_lock(&cgroup_root_mutex);
@@ -1106,14 +1104,8 @@ static int cgroup_show_options(struct se
 	if (root->flags & CGRP_ROOT_XATTR)
 		seq_puts(seq, ",xattr");
 
-	/* bindmount to attribute file? */
-	if (!S_ISDIR(dentry->d_inode->i_mode))
-		dentry = dentry->d_parent;
-	top_cgrp = dentry->d_fsdata;
-	/* release_agent is stored on top cgroup */
-	top_cgrp = &top_cgrp->root->top_cgroup;
-	if (top_cgrp->release_agent)
-		seq_printf(seq, ",release_agent=%s", top_cgrp->release_agent);
+	if (strlen(root->release_agent_path))
+		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
 
 	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
 		seq_puts(seq, ",clone_children");
@@ -1388,11 +1380,8 @@ static int cgroup_remount(struct super_b
 	/* re-populate subsystem files */
 	cgroup_populate_dir(cgrp, false, added_mask);
 
-	if (opts.release_agent) {
-		kfree(cgrp->release_agent);
-		cgrp->release_agent = opts.release_agent;
-		opts.release_agent = NULL;
-	}
+	if (opts.release_agent)
+		strcpy(root->release_agent_path, opts.release_agent);
  out_unlock:
 	kfree(opts.release_agent);
 	kfree(opts.name);
@@ -1505,6 +1494,8 @@ static struct cgroupfs_root *cgroup_root
 	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)
@@ -1702,9 +1693,7 @@ static struct dentry *cgroup_mount(struc
 		BUG_ON(!list_empty(&root_cgrp->children));
 		BUG_ON(root->number_of_cgroups != 1);
 
-		root_cgrp->release_agent = opts.release_agent;
 		root_cgrp->cgroup_ve = get_exec_env();
-		opts.release_agent = NULL;
 
 		cred = override_creds(&init_cred);
 		cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
@@ -2250,23 +2239,16 @@ static int cgroup_procs_write(struct cgr
 static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
 				      const char *buffer)
 {
-	char *release_agent;
+	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
 
 	if (strlen(buffer) >= PATH_MAX)
 		return -EINVAL;
 
-	release_agent = kstrdup(buffer, GFP_KERNEL);
-	if (!release_agent)
-		return -ENOMEM;
-
-	if (!cgroup_lock_live_group(cgrp)) {
-		kfree(release_agent);
+	if (!cgroup_lock_live_group(cgrp))
 		return -ENODEV;
-	}
 
 	mutex_lock(&cgroup_root_mutex);
-	kfree(cgrp->release_agent);
-	cgrp->release_agent = release_agent;
+	strcpy(cgrp->root->release_agent_path, buffer);
 	mutex_unlock(&cgroup_root_mutex);
 	mutex_unlock(&cgroup_mutex);
 	return 0;
@@ -2277,8 +2259,7 @@ static int cgroup_release_agent_show(str
 {
 	if (!cgroup_lock_live_group(cgrp))
 		return -ENODEV;
-	if (cgrp->release_agent)
-		seq_puts(seq, cgrp->release_agent);
+	seq_puts(seq, cgrp->root->release_agent_path);
 	seq_putc(seq, '\n');
 	mutex_unlock(&cgroup_mutex);
 	return 0;
@@ -5127,13 +5108,12 @@ static void cgroup_release_agent(struct
 						    release_list);
 		list_del_init(&cgrp->release_list);
 		raw_spin_unlock(&release_list_lock);
-
 		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
 		if (!pathbuf)
 			goto continue_free;
 		if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
 			goto continue_free;
-		agentbuf = kstrdup(cgrp->root->top_cgroup.release_agent, GFP_KERNEL);
+		agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
 		if (!agentbuf)
 			goto continue_free;