cgroup: remove cgroup->name
cgroup->name handling became quite complicated over time involving
dedicated struct cgroup_name for RCU protection. Now that cgroup is
on kernfs, we can drop all of it and simply use kernfs_name/path() and
friends. Replace cgroup->name and all related code with kernfs
name/path constructs.
* Reimplement cgroup_name() and cgroup_path() as thin wrappers on top
of kernfs counterparts, which involves semantic changes.
pr_cont_cgroup_name() and pr_cont_cgroup_path() added.
* cgroup->name handling dropped from cgroup_rename().
* All users of cgroup_name/path() updated to the new semantics. Users
which were formatting the string just to printk them are converted
to use pr_cont_cgroup_name/path() instead, which simplifies things
quite a bit. As cgroup_name() no longer requires RCU read lock
around it, RCU lockings which were protecting only cgroup_name() are
removed.
v2: Comment above oom_info_lock updated as suggested by Michal.
v3: dummy_top doesn't have a kn associated and
pr_cont_cgroup_name/path() ended up calling the matching kernfs
functions with NULL kn leading to oops. Test for NULL kn and
print "/" if so. This issue was reported by Fengguang Wu.
v4: Rebased on top of 0ab02ca8f887 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 59dfb02..638df032 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -145,8 +145,6 @@
/* hierarchy ID allocation and mapping, protected by cgroup_mutex */
static DEFINE_IDR(cgroup_hierarchy_idr);
-static struct cgroup_name root_cgroup_name = { .name = "/" };
-
/*
* Assign a monotonically increasing serial number to cgroups. It
* guarantees cgroups with bigger numbers are newer than those with smaller
@@ -888,17 +886,6 @@
static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
static const struct file_operations proc_cgroupstats_operations;
-static struct cgroup_name *cgroup_alloc_name(const char *name_str)
-{
- struct cgroup_name *name;
-
- name = kmalloc(sizeof(*name) + strlen(name_str) + 1, GFP_KERNEL);
- if (!name)
- return NULL;
- strcpy(name->name, name_str);
- return name;
-}
-
static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
char *buf)
{
@@ -958,8 +945,6 @@
cgroup_pidlist_destroy_all(cgrp);
kernfs_put(cgrp->kn);
-
- kfree(rcu_dereference_raw(cgrp->name));
kfree(cgrp);
}
@@ -1377,7 +1362,6 @@
INIT_LIST_HEAD(&root->root_list);
root->number_of_cgroups = 1;
cgrp->root = root;
- RCU_INIT_POINTER(cgrp->name, &root_cgroup_name);
init_cgroup_housekeeping(cgrp);
idr_init(&root->cgroup_idr);
}
@@ -1598,57 +1582,6 @@
static struct kobject *cgroup_kobj;
/**
- * cgroup_path - generate the path of a cgroup
- * @cgrp: the cgroup in question
- * @buf: the buffer to write the path into
- * @buflen: the length of the buffer
- *
- * Writes path of cgroup into buf. Returns 0 on success, -errno on error.
- *
- * We can't generate cgroup path using dentry->d_name, as accessing
- * dentry->name must be protected by irq-unsafe dentry->d_lock or parent
- * inode's i_mutex, while on the other hand cgroup_path() can be called
- * with some irq-safe spinlocks held.
- */
-int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
-{
- int ret = -ENAMETOOLONG;
- char *start;
-
- if (!cgrp->parent) {
- if (strlcpy(buf, "/", buflen) >= buflen)
- return -ENAMETOOLONG;
- return 0;
- }
-
- start = buf + buflen - 1;
- *start = '\0';
-
- rcu_read_lock();
- do {
- const char *name = cgroup_name(cgrp);
- int len;
-
- len = strlen(name);
- if ((start -= len) < buf)
- goto out;
- memcpy(start, name, len);
-
- if (--start < buf)
- goto out;
- *start = '/';
-
- cgrp = cgrp->parent;
- } while (cgrp->parent);
- ret = 0;
- memmove(buf, start, buf + buflen - start);
-out:
- rcu_read_unlock();
- return ret;
-}
-EXPORT_SYMBOL_GPL(cgroup_path);
-
-/**
* task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
* @task: target task
* @buf: the buffer to write the path into
@@ -1659,16 +1592,14 @@
* function grabs cgroup_mutex and shouldn't be used inside locks used by
* cgroup controller callbacks.
*
- * Returns 0 on success, fails with -%ENAMETOOLONG if @buflen is too short.
+ * Return value is the same as kernfs_path().
*/
-int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
+char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
{
struct cgroupfs_root *root;
struct cgroup *cgrp;
- int hierarchy_id = 1, ret = 0;
-
- if (buflen < 2)
- return -ENAMETOOLONG;
+ int hierarchy_id = 1;
+ char *path = NULL;
mutex_lock(&cgroup_mutex);
@@ -1676,14 +1607,15 @@
if (root) {
cgrp = task_cgroup_from_root(task, root);
- ret = cgroup_path(cgrp, buf, buflen);
+ path = cgroup_path(cgrp, buf, buflen);
} else {
/* if no hierarchy exists, everyone is in "/" */
- memcpy(buf, "/", 2);
+ if (strlcpy(buf, "/", buflen) < buflen)
+ path = buf;
}
mutex_unlock(&cgroup_mutex);
- return ret;
+ return path;
}
EXPORT_SYMBOL_GPL(task_cgroup_path);
@@ -2211,7 +2143,6 @@
const char *new_name_str)
{
struct cgroup *cgrp = kn->priv;
- struct cgroup_name *name, *old_name;
int ret;
if (kernfs_type(kn) != KERNFS_DIR)
@@ -2226,25 +2157,13 @@
if (cgroup_sane_behavior(cgrp))
return -EPERM;
- name = cgroup_alloc_name(new_name_str);
- if (!name)
- return -ENOMEM;
-
mutex_lock(&cgroup_tree_mutex);
mutex_lock(&cgroup_mutex);
ret = kernfs_rename(kn, new_parent, new_name_str);
- if (!ret) {
- old_name = rcu_dereference_protected(cgrp->name, true);
- rcu_assign_pointer(cgrp->name, name);
- } else {
- old_name = name;
- }
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgroup_tree_mutex);
-
- kfree_rcu(old_name, rcu_head);
return ret;
}
@@ -3719,14 +3638,13 @@
/**
* cgroup_create - create a cgroup
* @parent: cgroup that will be parent of the new cgroup
- * @name_str: name of the new cgroup
+ * @name: name of the new cgroup
* @mode: mode to set on new cgroup
*/
-static long cgroup_create(struct cgroup *parent, const char *name_str,
+static long cgroup_create(struct cgroup *parent, const char *name,
umode_t mode)
{
struct cgroup *cgrp;
- struct cgroup_name *name;
struct cgroupfs_root *root = parent->root;
int ssid, err;
struct cgroup_subsys *ss;
@@ -3737,13 +3655,6 @@
if (!cgrp)
return -ENOMEM;
- name = cgroup_alloc_name(name_str);
- if (!name) {
- err = -ENOMEM;
- goto err_free_cgrp;
- }
- rcu_assign_pointer(cgrp->name, name);
-
mutex_lock(&cgroup_tree_mutex);
/*
@@ -3781,7 +3692,7 @@
set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
/* create the directory */
- kn = kernfs_create_dir(parent->kn, name->name, mode, cgrp);
+ kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
if (IS_ERR(kn)) {
err = PTR_ERR(kn);
goto err_free_id;
@@ -3839,8 +3750,6 @@
mutex_unlock(&cgroup_mutex);
err_unlock_tree:
mutex_unlock(&cgroup_tree_mutex);
- kfree(rcu_dereference_raw(cgrp->name));
-err_free_cgrp:
kfree(cgrp);
return err;
@@ -4304,12 +4213,12 @@
{
struct pid *pid;
struct task_struct *tsk;
- char *buf;
+ char *buf, *path;
int retval;
struct cgroupfs_root *root;
retval = -ENOMEM;
- buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ buf = kmalloc(PATH_MAX, GFP_KERNEL);
if (!buf)
goto out;
@@ -4337,10 +4246,12 @@
root->name);
seq_putc(m, ':');
cgrp = task_cgroup_from_root(tsk, root);
- retval = cgroup_path(cgrp, buf, PAGE_SIZE);
- if (retval < 0)
+ path = cgroup_path(cgrp, buf, PATH_MAX);
+ if (!path) {
+ retval = -ENAMETOOLONG;
goto out_unlock;
- seq_puts(m, buf);
+ }
+ seq_puts(m, path);
seq_putc(m, '\n');
}
@@ -4588,16 +4499,17 @@
while (!list_empty(&release_list)) {
char *argv[3], *envp[3];
int i;
- char *pathbuf = NULL, *agentbuf = NULL;
+ char *pathbuf = NULL, *agentbuf = NULL, *path;
struct cgroup *cgrp = list_entry(release_list.next,
struct cgroup,
release_list);
list_del_init(&cgrp->release_list);
raw_spin_unlock(&release_list_lock);
- pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
if (!pathbuf)
goto continue_free;
- if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
+ path = cgroup_path(cgrp, pathbuf, PATH_MAX);
+ if (!path)
goto continue_free;
agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
if (!agentbuf)
@@ -4605,7 +4517,7 @@
i = 0;
argv[i++] = agentbuf;
- argv[i++] = pathbuf;
+ argv[i++] = path;
argv[i] = NULL;
i = 0;
@@ -4755,6 +4667,11 @@
{
struct cgrp_cset_link *link;
struct css_set *cset;
+ char *name_buf;
+
+ name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
+ if (!name_buf)
+ return -ENOMEM;
read_lock(&css_set_lock);
rcu_read_lock();
@@ -4763,14 +4680,17 @@
struct cgroup *c = link->cgrp;
const char *name = "?";
- if (c != cgroup_dummy_top)
- name = cgroup_name(c);
+ if (c != cgroup_dummy_top) {
+ cgroup_name(c, name_buf, NAME_MAX + 1);
+ name = name_buf;
+ }
seq_printf(seq, "Root %d group %s\n",
c->root->hierarchy_id, name);
}
rcu_read_unlock();
read_unlock(&css_set_lock);
+ kfree(name_buf);
return 0;
}
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 2d018c7..e97a6e8 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2088,10 +2088,9 @@
parent = parent_cs(parent);
if (cgroup_transfer_tasks(parent->css.cgroup, cs->css.cgroup)) {
- rcu_read_lock();
- printk(KERN_ERR "cpuset: failed to transfer tasks out of empty cpuset %s\n",
- cgroup_name(cs->css.cgroup));
- rcu_read_unlock();
+ printk(KERN_ERR "cpuset: failed to transfer tasks out of empty cpuset ");
+ pr_cont_cgroup_name(cs->css.cgroup);
+ pr_cont("\n");
}
}
@@ -2619,19 +2618,17 @@
/* Statically allocated to prevent using excess stack. */
static char cpuset_nodelist[CPUSET_NODELIST_LEN];
static DEFINE_SPINLOCK(cpuset_buffer_lock);
-
struct cgroup *cgrp = task_cs(tsk)->css.cgroup;
- rcu_read_lock();
spin_lock(&cpuset_buffer_lock);
nodelist_scnprintf(cpuset_nodelist, CPUSET_NODELIST_LEN,
tsk->mems_allowed);
- printk(KERN_INFO "%s cpuset=%s mems_allowed=%s\n",
- tsk->comm, cgroup_name(cgrp), cpuset_nodelist);
+ printk(KERN_INFO "%s cpuset=", tsk->comm);
+ pr_cont_cgroup_name(cgrp);
+ pr_cont(" mems_allowed=%s\n", cpuset_nodelist);
spin_unlock(&cpuset_buffer_lock);
- rcu_read_unlock();
}
/*
@@ -2681,12 +2678,12 @@
{
struct pid *pid;
struct task_struct *tsk;
- char *buf;
+ char *buf, *p;
struct cgroup_subsys_state *css;
int retval;
retval = -ENOMEM;
- buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ buf = kmalloc(PATH_MAX, GFP_KERNEL);
if (!buf)
goto out;
@@ -2696,14 +2693,16 @@
if (!tsk)
goto out_free;
+ retval = -ENAMETOOLONG;
rcu_read_lock();
css = task_css(tsk, cpuset_cgrp_id);
- retval = cgroup_path(css->cgroup, buf, PAGE_SIZE);
+ p = cgroup_path(css->cgroup, buf, PATH_MAX);
rcu_read_unlock();
- if (retval < 0)
+ if (!p)
goto out_put_task;
- seq_puts(m, buf);
+ seq_puts(m, p);
seq_putc(m, '\n');
+ retval = 0;
out_put_task:
put_task_struct(tsk);
out_free:
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index dd52e7f..30eee3b 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -111,8 +111,7 @@
if (autogroup_path(tg, group_path, PATH_MAX))
return group_path;
- cgroup_path(tg->css.cgroup, group_path, PATH_MAX);
- return group_path;
+ return cgroup_path(tg->css.cgroup, group_path, PATH_MAX);
}
#endif