cgroup: replace __DEVEL__sane_behavior with cgroup2 fs type

With major controllers - cpu, memory and io - shaping up for the
unified hierarchy, cgroup2 is about ready to be, gradually, released
into the wild.  Replace __DEVEL__sane_behavior flag which was used to
select the unified hierarchy with a separate filesystem type "cgroup2"
so that unified hierarchy can be mounted as follows.

  mount -t cgroup2 none $MOUNT_POINT

The cgroup2 fs has its own magic number - 0x63677270 ("cgrp").

v2: Assign a different magic number to cgroup2 fs.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
(cherry picked from commit 67e9c74b8a873408c27ac9a8e4c1d1c8d72c93ff)
Signed-off-by: Alex Shi <alex.shi@linaro.org>

diff --git a/Documentation/cgroups/unified-hierarchy.txt b/Documentation/cgroups/unified-hierarchy.txt
index 781b1d475bcfc9666d0d3dad80832c74adb48b22..c1f0e8780960a56c13e36a914d26c86a5a4a43de 100644 (file)
--- a/Documentation/cgroups/unified-hierarchy.txt
+++ b/Documentation/cgroups/unified-hierarchy.txt
@@ -94,11 +94,9 @@ the process.
 
 2-1. Mounting
 
-Currently, unified hierarchy can be mounted with the following mount
-command.  Note that this is still under development and scheduled to
-change soon.
+Unified hierarchy can be mounted with the following mount command.
 
- mount -t cgroup -o __DEVEL__sane_behavior cgroup $MOUNT_POINT
+ mount -t cgroup2 none $MOUNT_POINT
 
 All controllers which support the unified hierarchy and are not bound
 to other hierarchies are automatically bound to unified hierarchy and

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 8da26329975429c8895afcceab874d11e3326471..4cd5c95d1ca0ccbf59312d4ef3d92dae752b1c38 100644 (file)
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -66,7 +66,6 @@ enum {
 
 /* cgroup_root->flags */
 enum {
-       CGRP_ROOT_SANE_BEHAVIOR = (1 << 0), /* __DEVEL__sane_behavior specified */
        CGRP_ROOT_NOPREFIX      = (1 << 1), /* mounted subsystems have no named prefix */
        CGRP_ROOT_XATTR         = (1 << 2), /* supports extended attributes */
 };

diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index accb036bbc9c3621d9929dda225b6d0689348860..b283d56c1db97955f0558776fdc98e03294b7ce0 100644 (file)
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -54,6 +54,7 @@
 
 #define SMB_SUPER_MAGIC                0x517B
 #define CGROUP_SUPER_MAGIC     0x27e0eb
+#define CGROUP2_SUPER_MAGIC    0x63677270
 
 
 #define STACK_END_MAGIC                0x57AC6E9D

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 127c63e02d52b99d6c566ba50af719bde32f49c7..b5946676f84ef0013f07bcce35b10534dd23de04 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -211,6 +211,7 @@ static unsigned long have_free_callback __read_mostly;
 /* Ditto for the can_fork callback. */
 static unsigned long have_canfork_callback __read_mostly;
 
+static struct file_system_type cgroup2_fs_type;
 static struct cftype cgroup_dfl_base_files[];
 static struct cftype cgroup_legacy_base_files[];
 
@@ -1650,10 +1651,6 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
                        all_ss = true;
                        continue;
                }
-               if (!strcmp(token, "__DEVEL__sane_behavior")) {
-                       opts->flags |= CGRP_ROOT_SANE_BEHAVIOR;
-                       continue;
-               }
                if (!strcmp(token, "noprefix")) {
                        opts->flags |= CGRP_ROOT_NOPREFIX;
                        continue;
@@ -1720,15 +1717,6 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
                        return -ENOENT;
        }
 
-       if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
-               pr_warn("sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
-               if (nr_opts != 1) {
-                       pr_err("sane_behavior: no other mount options allowed\n");
-                       return -EINVAL;
-               }
-               return 0;
-       }
-
        /*
         * If the 'all' option was specified select all the subsystems,
         * otherwise if 'none', 'name=' and a subsystem name options were
@@ -2007,6 +1995,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
                         int flags, const char *unused_dev_name,
                         void *data)
 {
+       bool is_v2 = fs_type == &cgroup2_fs_type;
        struct super_block *pinned_sb = NULL;
        struct cgroup_subsys *ss;
        struct cgroup_root *root;
@@ -2023,6 +2012,17 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
        if (!use_task_css_set_links)
                cgroup_enable_task_cg_lists();
 
+       if (is_v2) {
+               if (data) {
+                       pr_err("cgroup2: unknown option \"%s\"\n", (char *)data);
+                       return ERR_PTR(-EINVAL);
+               }
+               cgrp_dfl_root_visible = true;
+               root = &cgrp_dfl_root;
+               cgroup_get(&root->cgrp);
+               goto out_mount;
+       }
+
        mutex_lock(&cgroup_mutex);
 
        /* First find the desired set of subsystems */
@@ -2030,15 +2030,6 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
        if (ret)
                goto out_unlock;
 
-       /* look for a matching existing root */
-       if (opts.flags & CGRP_ROOT_SANE_BEHAVIOR) {
-               cgrp_dfl_root_visible = true;
-               root = &cgrp_dfl_root;
-               cgroup_get(&root->cgrp);
-               ret = 0;
-               goto out_unlock;
-       }
-
        /*
         * Destruction of cgroup root is asynchronous, so subsystems may
         * still be dying after the previous unmount.  Let's drain the
@@ -2149,9 +2140,10 @@ out_free:
 
        if (ret)
                return ERR_PTR(ret);
-
+out_mount:
        dentry = kernfs_mount(fs_type, flags, root->kf_root,
-                               CGROUP_SUPER_MAGIC, &new_sb);
+                             is_v2 ? CGROUP2_SUPER_MAGIC : CGROUP_SUPER_MAGIC,
+                             &new_sb);
        if (IS_ERR(dentry) || !new_sb)
                cgroup_put(&root->cgrp);
 
@@ -2194,6 +2186,12 @@ static struct file_system_type cgroup_fs_type = {
        .kill_sb = cgroup_kill_sb,
 };
 
+static struct file_system_type cgroup2_fs_type = {
+       .name = "cgroup2",
+       .mount = cgroup_mount,
+       .kill_sb = cgroup_kill_sb,
+};
+
 /**
  * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
  * @task: target task
@@ -5383,6 +5381,7 @@ int __init cgroup_init(void)
 
        WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup"));
        WARN_ON(register_filesystem(&cgroup_fs_type));
+       WARN_ON(register_filesystem(&cgroup2_fs_type));
        WARN_ON(!proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations));
 
        return 0;