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Date: Thu, 13 Mar 2014 15:50:12 -0400
From: Tejun Heo <tj@...nel.org>
To: lizefan@...wei.com
Cc: cgroups@...r.kernel.org, containers@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>
Subject: [PATCH 10/11] 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@...nel.org>
---
include/linux/cgroup.h | 10 ++++++
kernel/cgroup.c | 94 ++++++++++++++++++++++++++++++++------------------
2 files changed, 71 insertions(+), 33 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 79993ac..7e9fa50 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -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.
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 36d1a53..c42230c 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -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);
--
1.8.5.3
--
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