Commit 67e9c74b authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
parent 34c06254

Documentation/cgroups/unified-hierarchy.txt

+2 −4
Original line number Diff line number Diff line
@@ -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

include/linux/cgroup-defs.h

+0 −1
Original line number Diff line number Diff line
@@ -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 */

};

include/uapi/linux/magic.h

+1 −0
Original line number Diff line number Diff line
@@ -54,6 +54,7 @@ 


#define SMB_SUPER_MAGIC		0x517B

#define CGROUP_SUPER_MAGIC	0x27e0eb

#define CGROUP2_SUPER_MAGIC	0x63677270





#define STACK_END_MAGIC		0x57AC6E9D

kernel/cgroup.c

+23 −24
Original line number Diff line number Diff line
@@ -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[];
@@ -1641,10 +1642,6 @@ 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;
@@ -1711,15 +1708,6 @@ 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
@@ -1998,6 +1986,7 @@ 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;
@@ -2014,6 +2003,17 @@ 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 */
@@ -2021,15 +2021,6 @@ 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
@@ -2140,9 +2131,10 @@ 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);
@@ -2185,6 +2177,12 @@ 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
@@ -5315,6 +5313,7 @@ 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;

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