[linux-2.6-block.git] / block / blk-cgroup.c

/*
 * Common Block IO controller cgroup interface
 *
 * Based on ideas and code from CFQ, CFS and BFQ:
 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
 *
 * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
 *		      Paolo Valente <paolo.valente@unimore.it>
 *
 * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
 * 	              Nauman Rafique <nauman@google.com>
 */
#include <linux/ioprio.h>
#include <linux/seq_file.h>
#include <linux/kdev_t.h>
#include <linux/module.h>
#include <linux/err.h>
#include "blk-cgroup.h"

static DEFINE_SPINLOCK(blkio_list_lock);
static LIST_HEAD(blkio_list);

struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
EXPORT_SYMBOL_GPL(blkio_root_cgroup);

bool blkiocg_css_tryget(struct blkio_cgroup *blkcg)
{
	if (!css_tryget(&blkcg->css))
		return false;
	return true;
}
EXPORT_SYMBOL_GPL(blkiocg_css_tryget);

void blkiocg_css_put(struct blkio_cgroup *blkcg)
{
	css_put(&blkcg->css);
}
EXPORT_SYMBOL_GPL(blkiocg_css_put);

struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
{
	return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
			    struct blkio_cgroup, css);
}
EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);

void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
			unsigned long time, unsigned long sectors)
{
	blkg->time += time;
	blkg->sectors += sectors;
}
EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_stats);

void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
			struct blkio_group *blkg, void *key, dev_t dev)
{
	unsigned long flags;

	spin_lock_irqsave(&blkcg->lock, flags);
	rcu_assign_pointer(blkg->key, key);
	blkg->blkcg_id = css_id(&blkcg->css);
	hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
	spin_unlock_irqrestore(&blkcg->lock, flags);
#ifdef CONFIG_DEBUG_BLK_CGROUP
	/* Need to take css reference ? */
	cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
#endif
	blkg->dev = dev;
}
EXPORT_SYMBOL_GPL(blkiocg_add_blkio_group);

static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
{
	hlist_del_init_rcu(&blkg->blkcg_node);
	blkg->blkcg_id = 0;
}

/*
 * returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
 * indicating that blk_group was unhashed by the time we got to it.
 */
int blkiocg_del_blkio_group(struct blkio_group *blkg)
{
	struct blkio_cgroup *blkcg;
	unsigned long flags;
	struct cgroup_subsys_state *css;
	int ret = 1;

	rcu_read_lock();
	css = css_lookup(&blkio_subsys, blkg->blkcg_id);
	if (!css)
		goto out;

	blkcg = container_of(css, struct blkio_cgroup, css);
	spin_lock_irqsave(&blkcg->lock, flags);
	if (!hlist_unhashed(&blkg->blkcg_node)) {
		__blkiocg_del_blkio_group(blkg);
		ret = 0;
	}
	spin_unlock_irqrestore(&blkcg->lock, flags);
out:
	rcu_read_unlock();
	return ret;
}
EXPORT_SYMBOL_GPL(blkiocg_del_blkio_group);

/* called under rcu_read_lock(). */
struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
{
	struct blkio_group *blkg;
	struct hlist_node *n;
	void *__key;

	hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
		__key = blkg->key;
		if (__key == key)
			return blkg;
	}

	return NULL;
}
EXPORT_SYMBOL_GPL(blkiocg_lookup_group);

#define SHOW_FUNCTION(__VAR)						\
static u64 blkiocg_##__VAR##_read(struct cgroup *cgroup,		\
				       struct cftype *cftype)		\
{									\
	struct blkio_cgroup *blkcg;					\
									\
	blkcg = cgroup_to_blkio_cgroup(cgroup);				\
	return (u64)blkcg->__VAR;					\
}

SHOW_FUNCTION(weight);
#undef SHOW_FUNCTION

static int
blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
{
	struct blkio_cgroup *blkcg;
	struct blkio_group *blkg;
	struct hlist_node *n;
	struct blkio_policy_type *blkiop;

	if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
		return -EINVAL;

	blkcg = cgroup_to_blkio_cgroup(cgroup);
	spin_lock_irq(&blkcg->lock);
	blkcg->weight = (unsigned int)val;
	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
		spin_lock(&blkio_list_lock);
		list_for_each_entry(blkiop, &blkio_list, list)
			blkiop->ops.blkio_update_group_weight_fn(blkg,
					blkcg->weight);
		spin_unlock(&blkio_list_lock);
	}
	spin_unlock_irq(&blkcg->lock);
	return 0;
}

#define SHOW_FUNCTION_PER_GROUP(__VAR)					\
static int blkiocg_##__VAR##_read(struct cgroup *cgroup,		\
			struct cftype *cftype, struct seq_file *m)	\
{									\
	struct blkio_cgroup *blkcg;					\
	struct blkio_group *blkg;					\
	struct hlist_node *n;						\
									\
	if (!cgroup_lock_live_group(cgroup))				\
		return -ENODEV;						\
									\
	blkcg = cgroup_to_blkio_cgroup(cgroup);				\
	rcu_read_lock();						\
	hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
		if (blkg->dev)						\
			seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev),	\
				 MINOR(blkg->dev), blkg->__VAR);	\
	}								\
	rcu_read_unlock();						\
	cgroup_unlock();						\
	return 0;							\
}

SHOW_FUNCTION_PER_GROUP(time);
SHOW_FUNCTION_PER_GROUP(sectors);
#ifdef CONFIG_DEBUG_BLK_CGROUP
SHOW_FUNCTION_PER_GROUP(dequeue);
#endif
#undef SHOW_FUNCTION_PER_GROUP

#ifdef CONFIG_DEBUG_BLK_CGROUP
void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
			unsigned long dequeue)
{
	blkg->dequeue += dequeue;
}
EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_dequeue_stats);
#endif

struct cftype blkio_files[] = {
	{
		.name = "weight",
		.read_u64 = blkiocg_weight_read,
		.write_u64 = blkiocg_weight_write,
	},
	{
		.name = "time",
		.read_seq_string = blkiocg_time_read,
	},
	{
		.name = "sectors",
		.read_seq_string = blkiocg_sectors_read,
	},
#ifdef CONFIG_DEBUG_BLK_CGROUP
       {
		.name = "dequeue",
		.read_seq_string = blkiocg_dequeue_read,
       },
#endif
};

static int blkiocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
{
	return cgroup_add_files(cgroup, subsys, blkio_files,
				ARRAY_SIZE(blkio_files));
}

static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
{
	struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
	unsigned long flags;
	struct blkio_group *blkg;
	void *key;
	struct blkio_policy_type *blkiop;

	rcu_read_lock();
remove_entry:
	spin_lock_irqsave(&blkcg->lock, flags);

	if (hlist_empty(&blkcg->blkg_list)) {
		spin_unlock_irqrestore(&blkcg->lock, flags);
		goto done;
	}

	blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
				blkcg_node);
	key = rcu_dereference(blkg->key);
	__blkiocg_del_blkio_group(blkg);

	spin_unlock_irqrestore(&blkcg->lock, flags);

	/*
	 * This blkio_group is being unlinked as associated cgroup is going
	 * away. Let all the IO controlling policies know about this event.
	 *
	 * Currently this is static call to one io controlling policy. Once
	 * we have more policies in place, we need some dynamic registration
	 * of callback function.
	 */
	spin_lock(&blkio_list_lock);
	list_for_each_entry(blkiop, &blkio_list, list)
		blkiop->ops.blkio_unlink_group_fn(key, blkg);
	spin_unlock(&blkio_list_lock);
	goto remove_entry;
done:
	free_css_id(&blkio_subsys, &blkcg->css);
	rcu_read_unlock();
	kfree(blkcg);
}

static struct cgroup_subsys_state *
blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
{
	struct blkio_cgroup *blkcg, *parent_blkcg;

	if (!cgroup->parent) {
		blkcg = &blkio_root_cgroup;
		goto done;
	}

	/* Currently we do not support hierarchy deeper than two level (0,1) */
	parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
	if (css_depth(&parent_blkcg->css) > 0)
		return ERR_PTR(-EINVAL);

	blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
	if (!blkcg)
		return ERR_PTR(-ENOMEM);

	blkcg->weight = BLKIO_WEIGHT_DEFAULT;
done:
	spin_lock_init(&blkcg->lock);
	INIT_HLIST_HEAD(&blkcg->blkg_list);

	return &blkcg->css;
}

/*
 * We cannot support shared io contexts, as we have no mean to support
 * two tasks with the same ioc in two different groups without major rework
 * of the main cic data structures.  For now we allow a task to change
 * its cgroup only if it's the only owner of its ioc.
 */
static int blkiocg_can_attach(struct cgroup_subsys *subsys,
				struct cgroup *cgroup, struct task_struct *tsk,
				bool threadgroup)
{
	struct io_context *ioc;
	int ret = 0;

	/* task_lock() is needed to avoid races with exit_io_context() */
	task_lock(tsk);
	ioc = tsk->io_context;
	if (ioc && atomic_read(&ioc->nr_tasks) > 1)
		ret = -EINVAL;
	task_unlock(tsk);

	return ret;
}

static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
				struct cgroup *prev, struct task_struct *tsk,
				bool threadgroup)
{
	struct io_context *ioc;

	task_lock(tsk);
	ioc = tsk->io_context;
	if (ioc)
		ioc->cgroup_changed = 1;
	task_unlock(tsk);
}

struct cgroup_subsys blkio_subsys = {
	.name = "blkio",
	.create = blkiocg_create,
	.can_attach = blkiocg_can_attach,
	.attach = blkiocg_attach,
	.destroy = blkiocg_destroy,
	.populate = blkiocg_populate,
	.subsys_id = blkio_subsys_id,
	.use_id = 1,
};

void blkio_policy_register(struct blkio_policy_type *blkiop)
{
	spin_lock(&blkio_list_lock);
	list_add_tail(&blkiop->list, &blkio_list);
	spin_unlock(&blkio_list_lock);
}
EXPORT_SYMBOL_GPL(blkio_policy_register);

void blkio_policy_unregister(struct blkio_policy_type *blkiop)
{
	spin_lock(&blkio_list_lock);
	list_del_init(&blkiop->list);
	spin_unlock(&blkio_list_lock);
}
EXPORT_SYMBOL_GPL(blkio_policy_unregister);
Commit	Line	Data
31e4c28d VG	1	/*
	2	* Common Block IO controller cgroup interface
	3	*
	4	* Based on ideas and code from CFQ, CFS and BFQ:
	5	* Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
	6	*
	7	* Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
	8	* Paolo Valente <paolo.valente@unimore.it>
	9	*
	10	* Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
	11	* Nauman Rafique <nauman@google.com>
	12	*/
	13	#include <linux/ioprio.h>
22084190 VG	14	#include <linux/seq_file.h>
22084190 VG	15	#include <linux/kdev_t.h>
9d6a986c	16	#include <linux/module.h>
accee785	17	#include <linux/err.h>
31e4c28d	18	#include "blk-cgroup.h"
3e252066 VG	19
	20	static DEFINE_SPINLOCK(blkio_list_lock);
	21	static LIST_HEAD(blkio_list);
b1c35769	22
31e4c28d	23	struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
9d6a986c VG	24	EXPORT_SYMBOL_GPL(blkio_root_cgroup);
	25
	26	bool blkiocg_css_tryget(struct blkio_cgroup *blkcg)
	27	{
	28	if (!css_tryget(&blkcg->css))
	29	return false;
	30	return true;
	31	}
	32	EXPORT_SYMBOL_GPL(blkiocg_css_tryget);
	33
	34	void blkiocg_css_put(struct blkio_cgroup *blkcg)
	35	{
	36	css_put(&blkcg->css);
	37	}
	38	EXPORT_SYMBOL_GPL(blkiocg_css_put);
31e4c28d VG	39
	40	struct blkio_cgroup cgroup_to_blkio_cgroup(struct cgroup cgroup)
	41	{
	42	return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
	43	struct blkio_cgroup, css);
	44	}
9d6a986c	45	EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
31e4c28d	46
22084190 VG	47	void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
	48	unsigned long time, unsigned long sectors)
	49	{
	50	blkg->time += time;
	51	blkg->sectors += sectors;
	52	}
9d6a986c	53	EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_stats);
22084190	54
31e4c28d	55	void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
22084190	56	struct blkio_group blkg, void key, dev_t dev)
31e4c28d VG	57	{
	58	unsigned long flags;
	59
	60	spin_lock_irqsave(&blkcg->lock, flags);
	61	rcu_assign_pointer(blkg->key, key);
b1c35769	62	blkg->blkcg_id = css_id(&blkcg->css);
31e4c28d VG	63	hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
31e4c28d VG	64	spin_unlock_irqrestore(&blkcg->lock, flags);
2868ef7b VG	65	#ifdef CONFIG_DEBUG_BLK_CGROUP
	66	/* Need to take css reference ? */
	67	cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
	68	#endif
22084190	69	blkg->dev = dev;
31e4c28d	70	}
9d6a986c	71	EXPORT_SYMBOL_GPL(blkiocg_add_blkio_group);
31e4c28d	72
b1c35769 VG	73	static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
	74	{
	75	hlist_del_init_rcu(&blkg->blkcg_node);
	76	blkg->blkcg_id = 0;
	77	}
	78
	79	/*
	80	* returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
	81	* indicating that blk_group was unhashed by the time we got to it.
	82	*/
31e4c28d VG	83	int blkiocg_del_blkio_group(struct blkio_group *blkg)
31e4c28d VG	84	{
b1c35769 VG	85	struct blkio_cgroup *blkcg;
	86	unsigned long flags;
	87	struct cgroup_subsys_state *css;
	88	int ret = 1;
	89
	90	rcu_read_lock();
	91	css = css_lookup(&blkio_subsys, blkg->blkcg_id);
	92	if (!css)
	93	goto out;
	94
	95	blkcg = container_of(css, struct blkio_cgroup, css);
	96	spin_lock_irqsave(&blkcg->lock, flags);
	97	if (!hlist_unhashed(&blkg->blkcg_node)) {
	98	__blkiocg_del_blkio_group(blkg);
	99	ret = 0;
	100	}
	101	spin_unlock_irqrestore(&blkcg->lock, flags);
	102	out:
	103	rcu_read_unlock();
	104	return ret;
31e4c28d	105	}
9d6a986c	106	EXPORT_SYMBOL_GPL(blkiocg_del_blkio_group);
31e4c28d VG	107
	108	/* called under rcu_read_lock(). */
	109	struct blkio_group blkiocg_lookup_group(struct blkio_cgroup blkcg, void *key)
	110	{
	111	struct blkio_group *blkg;
	112	struct hlist_node *n;
	113	void *__key;
	114
	115	hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
	116	__key = blkg->key;
	117	if (__key == key)
	118	return blkg;
	119	}
	120
	121	return NULL;
	122	}
9d6a986c	123	EXPORT_SYMBOL_GPL(blkiocg_lookup_group);
31e4c28d VG	124
	125	#define SHOW_FUNCTION(__VAR) \
	126	static u64 blkiocg_##__VAR##_read(struct cgroup *cgroup, \
	127	struct cftype *cftype) \
	128	{ \
	129	struct blkio_cgroup *blkcg; \
	130	\
	131	blkcg = cgroup_to_blkio_cgroup(cgroup); \
	132	return (u64)blkcg->__VAR; \
	133	}
	134
	135	SHOW_FUNCTION(weight);
	136	#undef SHOW_FUNCTION
	137
	138	static int
	139	blkiocg_weight_write(struct cgroup cgroup, struct cftype cftype, u64 val)
	140	{
	141	struct blkio_cgroup *blkcg;
f8d461d6 VG	142	struct blkio_group *blkg;
f8d461d6 VG	143	struct hlist_node *n;
3e252066	144	struct blkio_policy_type *blkiop;
31e4c28d VG	145
	146	if (val < BLKIO_WEIGHT_MIN \|\| val > BLKIO_WEIGHT_MAX)
	147	return -EINVAL;
	148
	149	blkcg = cgroup_to_blkio_cgroup(cgroup);
f8d461d6	150	spin_lock_irq(&blkcg->lock);
31e4c28d	151	blkcg->weight = (unsigned int)val;
3e252066 VG	152	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
	153	spin_lock(&blkio_list_lock);
	154	list_for_each_entry(blkiop, &blkio_list, list)
	155	blkiop->ops.blkio_update_group_weight_fn(blkg,
	156	blkcg->weight);
	157	spin_unlock(&blkio_list_lock);
	158	}
f8d461d6	159	spin_unlock_irq(&blkcg->lock);
31e4c28d VG	160	return 0;
	161	}
	162
22084190 VG	163	#define SHOW_FUNCTION_PER_GROUP(__VAR) \
	164	static int blkiocg_##__VAR##_read(struct cgroup *cgroup, \
	165	struct cftype cftype, struct seq_file m) \
	166	{ \
	167	struct blkio_cgroup *blkcg; \
	168	struct blkio_group *blkg; \
	169	struct hlist_node *n; \
	170	\
	171	if (!cgroup_lock_live_group(cgroup)) \
	172	return -ENODEV; \
	173	\
	174	blkcg = cgroup_to_blkio_cgroup(cgroup); \
	175	rcu_read_lock(); \
	176	hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
	177	if (blkg->dev) \
	178	seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev), \
	179	MINOR(blkg->dev), blkg->__VAR); \
	180	} \
	181	rcu_read_unlock(); \
	182	cgroup_unlock(); \
	183	return 0; \
	184	}
	185
	186	SHOW_FUNCTION_PER_GROUP(time);
	187	SHOW_FUNCTION_PER_GROUP(sectors);
	188	#ifdef CONFIG_DEBUG_BLK_CGROUP
	189	SHOW_FUNCTION_PER_GROUP(dequeue);
	190	#endif
	191	#undef SHOW_FUNCTION_PER_GROUP
	192
	193	#ifdef CONFIG_DEBUG_BLK_CGROUP
	194	void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
	195	unsigned long dequeue)
	196	{
	197	blkg->dequeue += dequeue;
	198	}
9d6a986c	199	EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_dequeue_stats);
22084190 VG	200	#endif
22084190 VG	201
31e4c28d VG	202	struct cftype blkio_files[] = {
	203	{
	204	.name = "weight",
	205	.read_u64 = blkiocg_weight_read,
	206	.write_u64 = blkiocg_weight_write,
	207	},
22084190 VG	208	{
	209	.name = "time",
	210	.read_seq_string = blkiocg_time_read,
	211	},
	212	{
	213	.name = "sectors",
	214	.read_seq_string = blkiocg_sectors_read,
	215	},
	216	#ifdef CONFIG_DEBUG_BLK_CGROUP
	217	{
	218	.name = "dequeue",
	219	.read_seq_string = blkiocg_dequeue_read,
	220	},
	221	#endif
31e4c28d VG	222	};
	223
	224	static int blkiocg_populate(struct cgroup_subsys subsys, struct cgroup cgroup)
	225	{
	226	return cgroup_add_files(cgroup, subsys, blkio_files,
	227	ARRAY_SIZE(blkio_files));
	228	}
	229
	230	static void blkiocg_destroy(struct cgroup_subsys subsys, struct cgroup cgroup)
	231	{
	232	struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
b1c35769 VG	233	unsigned long flags;
	234	struct blkio_group *blkg;
	235	void *key;
3e252066	236	struct blkio_policy_type *blkiop;
b1c35769 VG	237
	238	rcu_read_lock();
	239	remove_entry:
	240	spin_lock_irqsave(&blkcg->lock, flags);
	241
	242	if (hlist_empty(&blkcg->blkg_list)) {
	243	spin_unlock_irqrestore(&blkcg->lock, flags);
	244	goto done;
	245	}
	246
	247	blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
	248	blkcg_node);
	249	key = rcu_dereference(blkg->key);
	250	__blkiocg_del_blkio_group(blkg);
31e4c28d	251
b1c35769 VG	252	spin_unlock_irqrestore(&blkcg->lock, flags);
	253
	254	/*
	255	* This blkio_group is being unlinked as associated cgroup is going
	256	* away. Let all the IO controlling policies know about this event.
	257	*
	258	* Currently this is static call to one io controlling policy. Once
	259	* we have more policies in place, we need some dynamic registration
	260	* of callback function.
	261	*/
3e252066 VG	262	spin_lock(&blkio_list_lock);
	263	list_for_each_entry(blkiop, &blkio_list, list)
	264	blkiop->ops.blkio_unlink_group_fn(key, blkg);
	265	spin_unlock(&blkio_list_lock);
b1c35769 VG	266	goto remove_entry;
b1c35769 VG	267	done:
31e4c28d	268	free_css_id(&blkio_subsys, &blkcg->css);
b1c35769	269	rcu_read_unlock();
31e4c28d VG	270	kfree(blkcg);
	271	}
	272
	273	static struct cgroup_subsys_state *
	274	blkiocg_create(struct cgroup_subsys subsys, struct cgroup cgroup)
	275	{
	276	struct blkio_cgroup blkcg, parent_blkcg;
	277
	278	if (!cgroup->parent) {
	279	blkcg = &blkio_root_cgroup;
	280	goto done;
	281	}
	282
	283	/* Currently we do not support hierarchy deeper than two level (0,1) */
	284	parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
	285	if (css_depth(&parent_blkcg->css) > 0)
	286	return ERR_PTR(-EINVAL);
	287
	288	blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
	289	if (!blkcg)
	290	return ERR_PTR(-ENOMEM);
	291
	292	blkcg->weight = BLKIO_WEIGHT_DEFAULT;
	293	done:
	294	spin_lock_init(&blkcg->lock);
	295	INIT_HLIST_HEAD(&blkcg->blkg_list);
	296
	297	return &blkcg->css;
	298	}
	299
	300	/*
	301	* We cannot support shared io contexts, as we have no mean to support
	302	* two tasks with the same ioc in two different groups without major rework
	303	* of the main cic data structures. For now we allow a task to change
	304	* its cgroup only if it's the only owner of its ioc.
	305	*/
	306	static int blkiocg_can_attach(struct cgroup_subsys *subsys,
	307	struct cgroup cgroup, struct task_struct tsk,
	308	bool threadgroup)
	309	{
	310	struct io_context *ioc;
	311	int ret = 0;
	312
	313	/* task_lock() is needed to avoid races with exit_io_context() */
	314	task_lock(tsk);
	315	ioc = tsk->io_context;
	316	if (ioc && atomic_read(&ioc->nr_tasks) > 1)
	317	ret = -EINVAL;
	318	task_unlock(tsk);
	319
	320	return ret;
	321	}
	322
	323	static void blkiocg_attach(struct cgroup_subsys subsys, struct cgroup cgroup,
	324	struct cgroup prev, struct task_struct tsk,
	325	bool threadgroup)
	326	{
	327	struct io_context *ioc;
	328
	329	task_lock(tsk);
	330	ioc = tsk->io_context;
	331	if (ioc)
	332	ioc->cgroup_changed = 1;
	333	task_unlock(tsk);
334	}
335
336	struct cgroup_subsys blkio_subsys = {
337	.name = "blkio",
338	.create = blkiocg_create,
339	.can_attach = blkiocg_can_attach,
340	.attach = blkiocg_attach,
341	.destroy = blkiocg_destroy,
342	.populate = blkiocg_populate,
343	.subsys_id = blkio_subsys_id,
344	.use_id = 1,
345	};
3e252066 VG	346
	347	void blkio_policy_register(struct blkio_policy_type *blkiop)
	348	{
	349	spin_lock(&blkio_list_lock);
	350	list_add_tail(&blkiop->list, &blkio_list);
	351	spin_unlock(&blkio_list_lock);
	352	}
	353	EXPORT_SYMBOL_GPL(blkio_policy_register);
	354
	355	void blkio_policy_unregister(struct blkio_policy_type *blkiop)
	356	{
	357	spin_lock(&blkio_list_lock);
	358	list_del_init(&blkiop->list);
	359	spin_unlock(&blkio_list_lock);
	360	}
	361	EXPORT_SYMBOL_GPL(blkio_policy_unregister);