Merge branch 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

while the caller holds cgroup_mutex and it is ensured that either

attach() or cancel_attach() will be called in future.

void css_reset(struct cgroup_subsys_state *css)

(cgroup_mutex held by caller)

An optional operation which should restore @css's configuration to the

initial state.  This is currently only used on the unified hierarchy

when a subsystem is disabled on a cgroup through

"cgroup.subtree_control" but should remain enabled because other

subsystems depend on it.  cgroup core makes such a css invisible by

removing the associated interface files and invokes this callback so

that the hidden subsystem can return to the initial neutral state.

This prevents unexpected resource control from a hidden css and

ensures that the configuration is in the initial state when it is made

visible again later.

void cancel_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)

(cgroup_mutex held by caller)

 mount -t cgroup -o __DEVEL__sane_behavior cgroup $MOUNT_POINT

All controllers which are not bound to other hierarchies are

automatically bound to unified hierarchy and show up at the root of

it.  Controllers which are enabled only in the root of unified

hierarchy can be bound to other hierarchies at any time.  This allows

mixing unified hierarchy with the traditional multiple hierarchies in

a fully backward compatible way.

All controllers which support the unified hierarchy and are not bound

to other hierarchies are automatically bound to unified hierarchy and

show up at the root of it.  Controllers which are enabled only in the

root of unified hierarchy can be bound to other hierarchies.  This

allows mixing unified hierarchy with the traditional multiple

hierarchies in a fully backward compatible way.

For development purposes, the following boot parameter makes all

controllers to appear on the unified hierarchy whether supported or

not.

 cgroup__DEVEL__legacy_files_on_dfl

A controller can be moved across hierarchies only after the controller

is no longer referenced in its current hierarchy.  Because per-cgroup

controller states are destroyed asynchronously and controllers may

have lingering references, a controller may not show up immediately on

the unified hierarchy after the final umount of the previous

hierarchy.  Similarly, a controller should be fully disabled to be

moved out of the unified hierarchy and it may take some time for the

disabled controller to become available for other hierarchies;

furthermore, due to dependencies among controllers, other controllers

may need to be disabled too.

While useful for development and manual configurations, dynamically

moving controllers between the unified and other hierarchies is

strongly discouraged for production use.  It is recommended to decide

the hierarchies and controller associations before starting using the

controllers.

2-2. cgroup.subtree_control

	.css_offline = blkcg_css_offline,

	.css_free = blkcg_css_free,

	.can_attach = blkcg_can_attach,

	.base_cftypes = blkcg_files,

	.legacy_cftypes = blkcg_files,

#ifdef CONFIG_MEMCG

	/*

	 * This ensures that, if available, memcg is automatically enabled

	 * together on the default hierarchy so that the owner cgroup can

	 * be retrieved from writeback pages.

	 */

	.depends_on = 1 << memory_cgrp_id,

#endif

};

EXPORT_SYMBOL_GPL(blkio_cgrp_subsys);

	/* everything is in place, add intf files for the new policy */

	if (pol->cftypes)

		WARN_ON(cgroup_add_cftypes(&blkio_cgrp_subsys, pol->cftypes));

		WARN_ON(cgroup_add_legacy_cftypes(&blkio_cgrp_subsys,

						  pol->cftypes));

	ret = 0;

out_unlock:

	mutex_unlock(&blkcg_pol_mutex);

	int rw;

	/*

	 * If sane_hierarchy is enabled, we switch to properly hierarchical

	 * If on the default hierarchy, we switch to properly hierarchical

	 * behavior where limits on a given throtl_grp are applied to the

	 * whole subtree rather than just the group itself.  e.g. If 16M

	 * read_bps limit is set on the root group, the whole system can't

	 * exceed 16M for the device.

	 *

	 * If sane_hierarchy is not enabled, the broken flat hierarchy

	 * If not on the default hierarchy, the broken flat hierarchy

	 * behavior is retained where all throtl_grps are treated as if

	 * they're all separate root groups right below throtl_data.

	 * Limits of a group don't interact with limits of other groups

	 */

	parent_sq = &td->service_queue;

	if (cgroup_sane_behavior(blkg->blkcg->css.cgroup) && blkg->parent)

	if (cgroup_on_dfl(blkg->blkcg->css.cgroup) && blkg->parent)

		parent_sq = &blkg_to_tg(blkg->parent)->service_queue;

	throtl_service_queue_init(&tg->service_queue, parent_sq);

	struct kernfs_node *kn;		/* cgroup kernfs entry */

	struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */

	/* the bitmask of subsystems enabled on the child cgroups */

	/*

	 * The bitmask of subsystems enabled on the child cgroups.

	 * ->subtree_control is the one configured through

	 * "cgroup.subtree_control" while ->child_subsys_mask is the

	 * effective one which may have more subsystems enabled.

	 * Controller knobs are made available iff it's enabled in

	 * ->subtree_control.

	 */

	unsigned int subtree_control;

	unsigned int child_subsys_mask;

	/* Private pointers for each registered subsystem */

/* cgroup_root->flags */

enum {

	/*

	 * Unfortunately, cgroup core and various controllers are riddled

	 * with idiosyncrasies and pointless options.  The following flag,

	 * when set, will force sane behavior - some options are forced on,

	 * others are disallowed, and some controllers will change their

	 * hierarchical or other behaviors.

	 *

	 * The set of behaviors affected by this flag are still being

	 * determined and developed and the mount option for this flag is

	 * prefixed with __DEVEL__.  The prefix will be dropped once we

	 * reach the point where all behaviors are compatible with the

	 * planned unified hierarchy, which will automatically turn on this

	 * flag.

	 *

	 * The followings are the behaviors currently affected this flag.

	 *

	 * - Mount options "noprefix", "xattr", "clone_children",

	 *   "release_agent" and "name" are disallowed.

	 *

	 * - When mounting an existing superblock, mount options should

	 *   match.

	 *

	 * - Remount is disallowed.

	 *

	 * - rename(2) is disallowed.

	 *

	 * - "tasks" is removed.  Everything should be at process

	 *   granularity.  Use "cgroup.procs" instead.

	 *

	 * - "cgroup.procs" is not sorted.  pids will be unique unless they

	 *   got recycled inbetween reads.

	 *

	 * - "release_agent" and "notify_on_release" are removed.

	 *   Replacement notification mechanism will be implemented.

	 *

	 * - "cgroup.clone_children" is removed.

	 *

	 * - "cgroup.subtree_populated" is available.  Its value is 0 if

	 *   the cgroup and its descendants contain no task; otherwise, 1.

	 *   The file also generates kernfs notification which can be

	 *   monitored through poll and [di]notify when the value of the

	 *   file changes.

	 *

	 * - 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.

	 *

	 * - cpuset: a task can be moved into an empty cpuset, and again it

	 *   takes masks of ancestors.

	 *

	 * - memcg: use_hierarchy is on by default and the cgroup file for

	 *   the flag is not created.

	 *

	 * - blkcg: blk-throttle becomes properly hierarchical.

	 *

	 * - debug: disallowed on the default hierarchy.

	 */

	CGRP_ROOT_SANE_BEHAVIOR	= (1 << 0),

	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 */

	/* mount options live below bit 16 */

	CGRP_ROOT_OPTION_MASK	= (1 << 16) - 1,

};

/*

enum {

	CFTYPE_ONLY_ON_ROOT	= (1 << 0),	/* only create on root cgrp */

	CFTYPE_NOT_ON_ROOT	= (1 << 1),	/* don't create on root cgrp */

	CFTYPE_INSANE		= (1 << 2),	/* don't create if sane_behavior */

	CFTYPE_NO_PREFIX	= (1 << 3),	/* (DON'T USE FOR NEW FILES) no subsys prefix */

	CFTYPE_ONLY_ON_DFL	= (1 << 4),	/* only on default hierarchy */

	/* internal flags, do not use outside cgroup core proper */

	__CFTYPE_ONLY_ON_DFL	= (1 << 16),	/* only on default hierarchy */

	__CFTYPE_NOT_ON_DFL	= (1 << 17),	/* not on default hierarchy */

};

#define MAX_CFTYPE_NAME		64

extern struct cgroup_root cgrp_dfl_root;

extern struct css_set init_css_set;

/**

 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy

 * @cgrp: the cgroup of interest

 *

 * The default hierarchy is the v2 interface of cgroup and this function

 * can be used to test whether a cgroup is on the default hierarchy for

 * cases where a subsystem should behave differnetly depending on the

 * interface version.

 *

 * The set of behaviors which change on the default hierarchy are still

 * being determined and the mount option is prefixed with __DEVEL__.

 *

 * List of changed behaviors:

 *

 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"

 *   and "name" are disallowed.

 *

 * - When mounting an existing superblock, mount options should match.

 *

 * - Remount is disallowed.

 *

 * - rename(2) is disallowed.

 *

 * - "tasks" is removed.  Everything should be at process granularity.  Use

 *   "cgroup.procs" instead.

 *

 * - "cgroup.procs" is not sorted.  pids will be unique unless they got

 *   recycled inbetween reads.

 *

 * - "release_agent" and "notify_on_release" are removed.  Replacement

 *   notification mechanism will be implemented.

 *

 * - "cgroup.clone_children" is removed.

 *

 * - "cgroup.subtree_populated" is available.  Its value is 0 if the cgroup

 *   and its descendants contain no task; otherwise, 1.  The file also

 *   generates kernfs notification which can be monitored through poll and

 *   [di]notify when the value of the file changes.

 *

 * - 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.

 *

 * - cpuset: a task can be moved into an empty cpuset, and again it takes

 *   masks of ancestors.

 *

 * - memcg: use_hierarchy is on by default and the cgroup file for the flag

 *   is not created.

 *

 * - blkcg: blk-throttle becomes properly hierarchical.

 *

 * - debug: disallowed on the default hierarchy.

 */

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.

 */

static inline bool cgroup_sane_behavior(const struct cgroup *cgrp)

{

	return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR;

}

/* no synchronization, the result can only be used as a hint */

static inline bool cgroup_has_tasks(struct cgroup *cgrp)

{

char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);

int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);

int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);

int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);

int cgroup_rm_cftypes(struct cftype *cfts);

bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);

	int (*css_online)(struct cgroup_subsys_state *css);

	void (*css_offline)(struct cgroup_subsys_state *css);

	void (*css_free)(struct cgroup_subsys_state *css);

	void (*css_reset)(struct cgroup_subsys_state *css);

	int (*can_attach)(struct cgroup_subsys_state *css,

			  struct cgroup_taskset *tset);

	 */

	struct list_head cfts;

	/* base cftypes, automatically registered with subsys itself */

	struct cftype *base_cftypes;

	/*

	 * Base cftypes which are automatically registered.  The two can

	 * point to the same array.

	 */

	struct cftype *dfl_cftypes;	/* for the default hierarchy */

	struct cftype *legacy_cftypes;	/* for the legacy hierarchies */

	/*

	 * A subsystem may depend on other subsystems.  When such subsystem

	 * is enabled on a cgroup, the depended-upon subsystems are enabled

	 * together if available.  Subsystems enabled due to dependency are

	 * not visible to userland until explicitly enabled.  The following

	 * specifies the mask of subsystems that this one depends on.

	 */

	unsigned int depends_on;

};

#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;