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cgroup: make cgrp_dfl_root mountable 

cgrp_dfl_root will be used as the default unified hierarchy.  This
patch makes cgrp_dfl_root mountable by making the following changes.

* cgroup_init_early() now initializes cgrp_dfl_root w/
  CGRP_ROOT_SANE_BEHAVIOR.  The default hierarchy is always sane.

* parse_cgroupfs_options() and cgroup_mount() are updated such that
  cgrp_dfl_root is mounted if sane_behavior is specified w/o any
  subsystems.

* rebind_subsystems() now populates the root directory of
  cgrp_dfl_root.  Note that the function still guarantees success of
  rebinding subsystems to cgrp_dfl_root.  If populating fails while
  rebinding to cgrp_dfl_root, it whines but ignores the error.

* For backward compatibility, the default hierarchy shows up in
  /proc/$PID/cgroup only after it's explicitly mounted so that
  userland which doesn't make use of it doesn't see any change.

* "current_css_set_cg_links" file of debug cgroup now treats the
  default hierarchy the same as other hierarchies.  This is visible to
  userland.  Given that it's for debug controller, this should be
  fine.

* While at it, implement cgroup_on_dfl() which tests whether a give
  cgroup is on the default hierarchy or not.

The above changes make cgrp_dfl_root mostly equivalent to other
controllers but the actual unified hierarchy behaviors are not
implemented yet.  Let's plug child cgroup creation in cgrp_dfl_root
from create_cgroup() for now.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2014-03-19 10:23:55 -04:00
parent 4d3bb511b5
commit a2dd424750
2 changed files with 71 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
include/linux/cgroup.h
View File

@ -250,6 +250,9 @@ enum {
*
* - "cgroup.clone_children" is removed.
*
* - If mount is requested with sane_behavior but without any
* subsystem, the default unified hierarchy is mounted.
*
* - cpuset: tasks will be kept in empty cpusets when hotplug happens
* and take masks of ancestors with non-empty cpus/mems, instead of
* being moved to an ancestor.
@ -468,6 +471,13 @@ struct cftype {
#endif
};
extern struct cgroup_root cgrp_dfl_root;
static inline bool cgroup_on_dfl(const struct cgroup *cgrp)
{
return cgrp->root == &cgrp_dfl_root;
}
/*
* See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This
* function can be called as long as @cgrp is accessible.

94
kernel/cgroup.c
View File

@ -142,7 +142,13 @@ static const char *cgroup_subsys_name[] = {
* unattached - it never has more than a single cgroup, and all tasks are
* part of that cgroup.
*/
static struct cgroup_root cgrp_dfl_root;
struct cgroup_root cgrp_dfl_root;
/*
* The default hierarchy always exists but is hidden until mounted for the
* first time. This is for backward compatibility.
*/
static bool cgrp_dfl_root_visible;
/* The list of hierarchy roots */
@ -999,10 +1005,22 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
return -EBUSY;
}
if (dst_root != &cgrp_dfl_root) {
ret = cgroup_populate_dir(&dst_root->cgrp, ss_mask);
if (ret)
ret = cgroup_populate_dir(&dst_root->cgrp, ss_mask);
if (ret) {
if (dst_root != &cgrp_dfl_root)
return ret;
/*
* Rebinding back to the default root is not allowed to
* fail. Using both default and non-default roots should
* be rare. Moving subsystems back and forth even more so.
* Just warn about it and continue.
*/
if (cgrp_dfl_root_visible) {
pr_warning("cgroup: failed to create files (%d) while rebinding 0x%lx to default root\n",
ret, ss_mask);
pr_warning("cgroup: you may retry by moving them to a different hierarchy and unbinding\n");
}
}
/*
@ -1011,7 +1029,7 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
*/
mutex_unlock(&cgroup_mutex);
for_each_subsys(ss, ssid)
if ((ss_mask & (1 << ssid)) && ss->root != &cgrp_dfl_root)
if (ss_mask & (1 << ssid))
cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
mutex_lock(&cgroup_mutex);
@ -1039,8 +1057,7 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
ss->bind(css);
}
if (dst_root != &cgrp_dfl_root)
kernfs_activate(dst_root->cgrp.kn);
kernfs_activate(dst_root->cgrp.kn);
return 0;
}
@ -1190,16 +1207,6 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
return -ENOENT;
}
/*
* If the 'all' option was specified select all the subsystems,
* otherwise if 'none', 'name=' and a subsystem name options
* were not specified, let's default to 'all'
*/
if (all_ss || (!one_ss && !opts->none && !opts->name))
for_each_subsys(ss, i)
if (!ss->disabled)
set_bit(i, &opts->subsys_mask);
/* Consistency checks */
if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
@ -1211,6 +1218,23 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
pr_err("cgroup: sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n");
return -EINVAL;
}
} else {
/*
* If the 'all' option was specified select all the
* subsystems, otherwise if 'none', 'name=' and a subsystem
* name options were not specified, let's default to 'all'
*/
if (all_ss || (!one_ss && !opts->none && !opts->name))
for_each_subsys(ss, i)
if (!ss->disabled)
set_bit(i, &opts->subsys_mask);
/*
* We either have to specify by name or by subsystems. (So
* all empty hierarchies must have a name).
*/
if (!opts->subsys_mask && !opts->name)
return -EINVAL;
}
/*
@ -1226,13 +1250,6 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
if (opts->subsys_mask && opts->none)
return -EINVAL;
/*
* We either have to specify by name or by subsystems. (So all
* empty hierarchies must have a name).
*/
if (!opts->subsys_mask && !opts->name)
return -EINVAL;
return 0;
}
@ -1487,6 +1504,14 @@ retry:
goto out_unlock;
/* look for a matching existing root */
if (!opts.subsys_mask && !opts.none && !opts.name) {
cgrp_dfl_root_visible = true;
root = &cgrp_dfl_root;
cgroup_get(&root->cgrp);
ret = 0;
goto out_unlock;
}
for_each_root(root) {
bool name_match = false;
@ -3622,6 +3647,13 @@ static long cgroup_create(struct cgroup *parent, const char *name,
struct cgroup_subsys *ss;
struct kernfs_node *kn;
/*
* XXX: The default hierarchy isn't fully implemented yet. Block
* !root cgroup creation on it for now.
*/
if (root == &cgrp_dfl_root)
return -EINVAL;
/* allocate the cgroup and its ID, 0 is reserved for the root */
cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
if (!cgrp)
@ -4061,7 +4093,8 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
*/
int __init cgroup_init_early(void)
{
static struct cgroup_sb_opts __initdata opts = { };
static struct cgroup_sb_opts __initdata opts =
{ .flags = CGRP_ROOT_SANE_BEHAVIOR };
struct cgroup_subsys *ss;
int i;
@ -4198,7 +4231,7 @@ int proc_cgroup_show(struct seq_file *m, void *v)
struct cgroup *cgrp;
int ssid, count = 0;
if (root == &cgrp_dfl_root)
if (root == &cgrp_dfl_root && !cgrp_dfl_root_visible)
continue;
seq_printf(m, "%d:", root->hierarchy_id);
@ -4631,15 +4664,10 @@ static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
cset = rcu_dereference(current->cgroups);
list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
struct cgroup *c = link->cgrp;
const char *name = "?";
if (c != &cgrp_dfl_root.cgrp) {
cgroup_name(c, name_buf, NAME_MAX + 1);
name = name_buf;
}
cgroup_name(c, name_buf, NAME_MAX + 1);
seq_printf(seq, "Root %d group %s\n",
c->root->hierarchy_id, name);
c->root->hierarchy_id, name_buf);
}
rcu_read_unlock();
up_read(&css_set_rwsem);