block/blk-cgroup.h - kernel/msm-5.4 - Gitiles

 #ifndef _BLK_CGROUP_H
 #define _BLK_CGROUP_H
 /*
  * 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/cgroup.h>
 #include <linux/u64_stats_sync.h>
 #include <linux/seq_file.h>

 enum blkio_policy_id {
 	BLKIO_POLICY_PROP = 0,		/* Proportional Bandwidth division */
 	BLKIO_POLICY_THROTL,		/* Throttling */

 	BLKIO_NR_POLICIES,
 };

 /* Max limits for throttle policy */
 #define THROTL_IOPS_MAX		UINT_MAX

 #ifdef CONFIG_BLK_CGROUP

 /* CFQ specific, out here for blkcg->cfq_weight */
 #define CFQ_WEIGHT_MIN		10
 #define CFQ_WEIGHT_MAX		1000
 #define CFQ_WEIGHT_DEFAULT	500

 enum blkg_rwstat_type {
 	BLKG_RWSTAT_READ,
 	BLKG_RWSTAT_WRITE,
 	BLKG_RWSTAT_SYNC,
 	BLKG_RWSTAT_ASYNC,

 	BLKG_RWSTAT_NR,
 	BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR,
 };

 struct blkio_cgroup {
 	struct cgroup_subsys_state css;
 	spinlock_t lock;
 	struct hlist_head blkg_list;

 	/* for policies to test whether associated blkcg has changed */
 	uint64_t id;

 	/* TODO: per-policy storage in blkio_cgroup */
 	unsigned int cfq_weight;	/* belongs to cfq */
 };

 struct blkg_stat {
 	struct u64_stats_sync		syncp;
 	uint64_t			cnt;
 };

 struct blkg_rwstat {
 	struct u64_stats_sync		syncp;
 	uint64_t			cnt[BLKG_RWSTAT_NR];
 };

 /* per-blkg per-policy data */
 struct blkg_policy_data {
 	/* the blkg this per-policy data belongs to */
 	struct blkio_group *blkg;

 	/* pol->pdata_size bytes of private data used by policy impl */
 	char pdata[] __aligned(__alignof__(unsigned long long));
 };

 struct blkio_group {
 	/* Pointer to the associated request_queue */
 	struct request_queue *q;
 	struct list_head q_node;
 	struct hlist_node blkcg_node;
 	struct blkio_cgroup *blkcg;
 	/* Store cgroup path */
 	char path[128];
 	/* reference count */
 	int refcnt;

 	struct blkg_policy_data *pd[BLKIO_NR_POLICIES];

 	struct rcu_head rcu_head;
 };

 typedef void (blkio_init_group_fn)(struct blkio_group *blkg);
 typedef void (blkio_exit_group_fn)(struct blkio_group *blkg);
 typedef void (blkio_reset_group_stats_fn)(struct blkio_group *blkg);

 struct blkio_policy_ops {
 	blkio_init_group_fn *blkio_init_group_fn;
 	blkio_exit_group_fn *blkio_exit_group_fn;
 	blkio_reset_group_stats_fn *blkio_reset_group_stats_fn;
 };

 struct blkio_policy_type {
 	struct list_head list;
 	struct blkio_policy_ops ops;
 	enum blkio_policy_id plid;
 	size_t pdata_size;		/* policy specific private data size */
 	struct cftype *cftypes;		/* cgroup files for the policy */
 };

 extern int blkcg_init_queue(struct request_queue *q);
 extern void blkcg_drain_queue(struct request_queue *q);
 extern void blkcg_exit_queue(struct request_queue *q);

 /* Blkio controller policy registration */
 extern void blkio_policy_register(struct blkio_policy_type *);
 extern void blkio_policy_unregister(struct blkio_policy_type *);
 extern void blkg_destroy_all(struct request_queue *q, bool destroy_root);
 extern void update_root_blkg_pd(struct request_queue *q,
 				enum blkio_policy_id plid);

 void blkcg_print_blkgs(struct seq_file *sf, struct blkio_cgroup *blkcg,
 		       u64 (*prfill)(struct seq_file *, void *, int),
 		       int pol, int data, bool show_total);
 u64 __blkg_prfill_u64(struct seq_file *sf, void *pdata, u64 v);
 u64 __blkg_prfill_rwstat(struct seq_file *sf, void *pdata,
 			 const struct blkg_rwstat *rwstat);
 u64 blkg_prfill_stat(struct seq_file *sf, void *pdata, int off);
 u64 blkg_prfill_rwstat(struct seq_file *sf, void *pdata, int off);

 struct blkg_conf_ctx {
 	struct gendisk		*disk;
 	struct blkio_group	*blkg;
 	u64			v;
 };

 int blkg_conf_prep(struct blkio_cgroup *blkcg, const char *input,
 		   struct blkg_conf_ctx *ctx);
 void blkg_conf_finish(struct blkg_conf_ctx *ctx);


 /**
  * blkg_to_pdata - get policy private data
  * @blkg: blkg of interest
  * @pol: policy of interest
  *
  * Return pointer to private data associated with the @blkg-@pol pair.
  */
 static inline void *blkg_to_pdata(struct blkio_group *blkg,
 			      struct blkio_policy_type *pol)
 {
 	return blkg ? blkg->pd[pol->plid]->pdata : NULL;
 }

 /**
  * pdata_to_blkg - get blkg associated with policy private data
  * @pdata: policy private data of interest
  *
  * @pdata is policy private data.  Determine the blkg it's associated with.
  */
 static inline struct blkio_group *pdata_to_blkg(void *pdata)
 {
 	if (pdata) {
 		struct blkg_policy_data *pd =
 			container_of(pdata, struct blkg_policy_data, pdata);
 		return pd->blkg;
 	}
 	return NULL;
 }

 static inline char *blkg_path(struct blkio_group *blkg)
 {
 	return blkg->path;
 }

 /**
  * blkg_get - get a blkg reference
  * @blkg: blkg to get
  *
  * The caller should be holding queue_lock and an existing reference.
  */
 static inline void blkg_get(struct blkio_group *blkg)
 {
 	lockdep_assert_held(blkg->q->queue_lock);
 	WARN_ON_ONCE(!blkg->refcnt);
 	blkg->refcnt++;
 }

 void __blkg_release(struct blkio_group *blkg);

 /**
  * blkg_put - put a blkg reference
  * @blkg: blkg to put
  *
  * The caller should be holding queue_lock.
  */
 static inline void blkg_put(struct blkio_group *blkg)
 {
 	lockdep_assert_held(blkg->q->queue_lock);
 	WARN_ON_ONCE(blkg->refcnt <= 0);
 	if (!--blkg->refcnt)
 		__blkg_release(blkg);
 }

 /**
  * blkg_stat_add - add a value to a blkg_stat
  * @stat: target blkg_stat
  * @val: value to add
  *
  * Add @val to @stat.  The caller is responsible for synchronizing calls to
  * this function.
  */
 static inline void blkg_stat_add(struct blkg_stat *stat, uint64_t val)
 {
 	u64_stats_update_begin(&stat->syncp);
 	stat->cnt += val;
 	u64_stats_update_end(&stat->syncp);
 }

 /**
  * blkg_stat_read - read the current value of a blkg_stat
  * @stat: blkg_stat to read
  *
  * Read the current value of @stat.  This function can be called without
  * synchroniztion and takes care of u64 atomicity.
  */
 static inline uint64_t blkg_stat_read(struct blkg_stat *stat)
 {
 	unsigned int start;
 	uint64_t v;

 	do {
 		start = u64_stats_fetch_begin(&stat->syncp);
 		v = stat->cnt;
 	} while (u64_stats_fetch_retry(&stat->syncp, start));

 	return v;
 }

 /**
  * blkg_stat_reset - reset a blkg_stat
  * @stat: blkg_stat to reset
  */
 static inline void blkg_stat_reset(struct blkg_stat *stat)
 {
 	stat->cnt = 0;
 }

 /**
  * blkg_rwstat_add - add a value to a blkg_rwstat
  * @rwstat: target blkg_rwstat
  * @rw: mask of REQ_{WRITE|SYNC}
  * @val: value to add
  *
  * Add @val to @rwstat.  The counters are chosen according to @rw.  The
  * caller is responsible for synchronizing calls to this function.
  */
 static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
 				   int rw, uint64_t val)
 {
 	u64_stats_update_begin(&rwstat->syncp);

 	if (rw & REQ_WRITE)
 		rwstat->cnt[BLKG_RWSTAT_WRITE] += val;
 	else
 		rwstat->cnt[BLKG_RWSTAT_READ] += val;
 	if (rw & REQ_SYNC)
 		rwstat->cnt[BLKG_RWSTAT_SYNC] += val;
 	else
 		rwstat->cnt[BLKG_RWSTAT_ASYNC] += val;

 	u64_stats_update_end(&rwstat->syncp);
 }

 /**
  * blkg_rwstat_read - read the current values of a blkg_rwstat
  * @rwstat: blkg_rwstat to read
  *
  * Read the current snapshot of @rwstat and return it as the return value.
  * This function can be called without synchronization and takes care of
  * u64 atomicity.
  */
 static struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)
 {
 	unsigned int start;
 	struct blkg_rwstat tmp;

 	do {
 		start = u64_stats_fetch_begin(&rwstat->syncp);
 		tmp = *rwstat;
 	} while (u64_stats_fetch_retry(&rwstat->syncp, start));

 	return tmp;
 }

 /**
  * blkg_rwstat_sum - read the total count of a blkg_rwstat
  * @rwstat: blkg_rwstat to read
  *
  * Return the total count of @rwstat regardless of the IO direction.  This
  * function can be called without synchronization and takes care of u64
  * atomicity.
  */
 static inline uint64_t blkg_rwstat_sum(struct blkg_rwstat *rwstat)
 {
 	struct blkg_rwstat tmp = blkg_rwstat_read(rwstat);

 	return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE];
 }

 /**
  * blkg_rwstat_reset - reset a blkg_rwstat
  * @rwstat: blkg_rwstat to reset
  */
 static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat)
 {
 	memset(rwstat->cnt, 0, sizeof(rwstat->cnt));
 }

 #else

 struct blkio_group {
 };

 struct blkio_policy_type {
 };

 static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
 static inline void blkcg_drain_queue(struct request_queue *q) { }
 static inline void blkcg_exit_queue(struct request_queue *q) { }
 static inline void blkio_policy_register(struct blkio_policy_type *blkiop) { }
 static inline void blkio_policy_unregister(struct blkio_policy_type *blkiop) { }
 static inline void blkg_destroy_all(struct request_queue *q,
 				    bool destory_root) { }
 static inline void update_root_blkg_pd(struct request_queue *q,
 				       enum blkio_policy_id plid) { }

 static inline void *blkg_to_pdata(struct blkio_group *blkg,
 				struct blkio_policy_type *pol) { return NULL; }
 static inline struct blkio_group *pdata_to_blkg(void *pdata,
 				struct blkio_policy_type *pol) { return NULL; }
 static inline char *blkg_path(struct blkio_group *blkg) { return NULL; }
 static inline void blkg_get(struct blkio_group *blkg) { }
 static inline void blkg_put(struct blkio_group *blkg) { }

 #endif

 #ifdef CONFIG_BLK_CGROUP
 extern struct blkio_cgroup blkio_root_cgroup;
 extern struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup);
 extern struct blkio_cgroup *bio_blkio_cgroup(struct bio *bio);
 extern struct blkio_group *blkg_lookup(struct blkio_cgroup *blkcg,
 				       struct request_queue *q);
 struct blkio_group *blkg_lookup_create(struct blkio_cgroup *blkcg,
 				       struct request_queue *q,
 				       bool for_root);
 #else
 struct cgroup;
 static inline struct blkio_cgroup *
 cgroup_to_blkio_cgroup(struct cgroup *cgroup) { return NULL; }
 static inline struct blkio_cgroup *
 bio_blkio_cgroup(struct bio *bio) { return NULL; }

 static inline struct blkio_group *blkg_lookup(struct blkio_cgroup *blkcg,
 					      void *key) { return NULL; }
 #endif
 #endif /* _BLK_CGROUP_H */
	#ifndef _BLK_CGROUP_H
	#define _BLK_CGROUP_H
	/*
	* 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/cgroup.h>
	#include <linux/u64_stats_sync.h>
	#include <linux/seq_file.h>

	enum blkio_policy_id {
	BLKIO_POLICY_PROP = 0, /* Proportional Bandwidth division */
	BLKIO_POLICY_THROTL, /* Throttling */

	BLKIO_NR_POLICIES,
	};

	/* Max limits for throttle policy */
	#define THROTL_IOPS_MAX UINT_MAX

	#ifdef CONFIG_BLK_CGROUP

	/* CFQ specific, out here for blkcg->cfq_weight */
	#define CFQ_WEIGHT_MIN 10
	#define CFQ_WEIGHT_MAX 1000
	#define CFQ_WEIGHT_DEFAULT 500

	enum blkg_rwstat_type {
	BLKG_RWSTAT_READ,
	BLKG_RWSTAT_WRITE,
	BLKG_RWSTAT_SYNC,
	BLKG_RWSTAT_ASYNC,

	BLKG_RWSTAT_NR,
	BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR,
	};

	struct blkio_cgroup {
	struct cgroup_subsys_state css;
	spinlock_t lock;
	struct hlist_head blkg_list;

	/* for policies to test whether associated blkcg has changed */
	uint64_t id;

	/* TODO: per-policy storage in blkio_cgroup */
	unsigned int cfq_weight; /* belongs to cfq */
	};

	struct blkg_stat {
	struct u64_stats_sync syncp;
	uint64_t cnt;
	};

	struct blkg_rwstat {
	struct u64_stats_sync syncp;
	uint64_t cnt[BLKG_RWSTAT_NR];
	};

	/* per-blkg per-policy data */
	struct blkg_policy_data {
	/* the blkg this per-policy data belongs to */
	struct blkio_group *blkg;

	/* pol->pdata_size bytes of private data used by policy impl */
	char pdata[] __aligned(__alignof__(unsigned long long));
	};

	struct blkio_group {
	/* Pointer to the associated request_queue */
	struct request_queue *q;
	struct list_head q_node;
	struct hlist_node blkcg_node;
	struct blkio_cgroup *blkcg;
	/* Store cgroup path */
	char path[128];
	/* reference count */
	int refcnt;

	struct blkg_policy_data *pd[BLKIO_NR_POLICIES];

	struct rcu_head rcu_head;
	};

	typedef void (blkio_init_group_fn)(struct blkio_group *blkg);
	typedef void (blkio_exit_group_fn)(struct blkio_group *blkg);
	typedef void (blkio_reset_group_stats_fn)(struct blkio_group *blkg);

	struct blkio_policy_ops {
	blkio_init_group_fn *blkio_init_group_fn;
	blkio_exit_group_fn *blkio_exit_group_fn;
	blkio_reset_group_stats_fn *blkio_reset_group_stats_fn;
	};

	struct blkio_policy_type {
	struct list_head list;
	struct blkio_policy_ops ops;
	enum blkio_policy_id plid;
	size_t pdata_size; /* policy specific private data size */
	struct cftype cftypes; / cgroup files for the policy */
	};

	extern int blkcg_init_queue(struct request_queue *q);
	extern void blkcg_drain_queue(struct request_queue *q);
	extern void blkcg_exit_queue(struct request_queue *q);

	/* Blkio controller policy registration */
	extern void blkio_policy_register(struct blkio_policy_type *);
	extern void blkio_policy_unregister(struct blkio_policy_type *);
	extern void blkg_destroy_all(struct request_queue *q, bool destroy_root);
	extern void update_root_blkg_pd(struct request_queue *q,
	enum blkio_policy_id plid);

	void blkcg_print_blkgs(struct seq_file sf, struct blkio_cgroup blkcg,
	u64 (prfill)(struct seq_file , void *, int),
	int pol, int data, bool show_total);
	u64 __blkg_prfill_u64(struct seq_file sf, void pdata, u64 v);
	u64 __blkg_prfill_rwstat(struct seq_file sf, void pdata,
	const struct blkg_rwstat *rwstat);
	u64 blkg_prfill_stat(struct seq_file sf, void pdata, int off);
	u64 blkg_prfill_rwstat(struct seq_file sf, void pdata, int off);

	struct blkg_conf_ctx {
	struct gendisk *disk;
	struct blkio_group *blkg;
	u64 v;
	};

	int blkg_conf_prep(struct blkio_cgroup blkcg, const char input,
	struct blkg_conf_ctx *ctx);
	void blkg_conf_finish(struct blkg_conf_ctx *ctx);


	/**
	* blkg_to_pdata - get policy private data
	* @blkg: blkg of interest
	* @pol: policy of interest
	*
	* Return pointer to private data associated with the @blkg-@pol pair.
	*/
	static inline void blkg_to_pdata(struct blkio_group blkg,
	struct blkio_policy_type *pol)
	{
	return blkg ? blkg->pd[pol->plid]->pdata : NULL;
	}

	/**
	* pdata_to_blkg - get blkg associated with policy private data
	* @pdata: policy private data of interest
	*
	* @pdata is policy private data. Determine the blkg it's associated with.
	*/
	static inline struct blkio_group pdata_to_blkg(void pdata)
	{
	if (pdata) {
	struct blkg_policy_data *pd =
	container_of(pdata, struct blkg_policy_data, pdata);
	return pd->blkg;
	}
	return NULL;
	}

	static inline char blkg_path(struct blkio_group blkg)
	{
	return blkg->path;
	}

	/**
	* blkg_get - get a blkg reference
	* @blkg: blkg to get
	*
	* The caller should be holding queue_lock and an existing reference.
	*/
	static inline void blkg_get(struct blkio_group *blkg)
	{
	lockdep_assert_held(blkg->q->queue_lock);
	WARN_ON_ONCE(!blkg->refcnt);
	blkg->refcnt++;
	}

	void __blkg_release(struct blkio_group *blkg);

	/**
	* blkg_put - put a blkg reference
	* @blkg: blkg to put
	*
	* The caller should be holding queue_lock.
	*/
	static inline void blkg_put(struct blkio_group *blkg)
	{
	lockdep_assert_held(blkg->q->queue_lock);
	WARN_ON_ONCE(blkg->refcnt <= 0);
	if (!--blkg->refcnt)
	__blkg_release(blkg);
	}

	/**
	* blkg_stat_add - add a value to a blkg_stat
	* @stat: target blkg_stat
	* @val: value to add
	*
	* Add @val to @stat. The caller is responsible for synchronizing calls to
	* this function.
	*/
	static inline void blkg_stat_add(struct blkg_stat *stat, uint64_t val)
	{
	u64_stats_update_begin(&stat->syncp);
	stat->cnt += val;
	u64_stats_update_end(&stat->syncp);
	}

	/**
	* blkg_stat_read - read the current value of a blkg_stat
	* @stat: blkg_stat to read
	*
	* Read the current value of @stat. This function can be called without
	* synchroniztion and takes care of u64 atomicity.
	*/
	static inline uint64_t blkg_stat_read(struct blkg_stat *stat)
	{
	unsigned int start;
	uint64_t v;

	do {
	start = u64_stats_fetch_begin(&stat->syncp);
	v = stat->cnt;
	} while (u64_stats_fetch_retry(&stat->syncp, start));

	return v;
	}

	/**
	* blkg_stat_reset - reset a blkg_stat
	* @stat: blkg_stat to reset
	*/
	static inline void blkg_stat_reset(struct blkg_stat *stat)
	{
	stat->cnt = 0;
	}

	/**
	* blkg_rwstat_add - add a value to a blkg_rwstat
	* @rwstat: target blkg_rwstat
	* @rw: mask of REQ_{WRITE\|SYNC}
	* @val: value to add
	*
	* Add @val to @rwstat. The counters are chosen according to @rw. The
	* caller is responsible for synchronizing calls to this function.
	*/
	static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
	int rw, uint64_t val)
	{
	u64_stats_update_begin(&rwstat->syncp);

	if (rw & REQ_WRITE)
	rwstat->cnt[BLKG_RWSTAT_WRITE] += val;
	else
	rwstat->cnt[BLKG_RWSTAT_READ] += val;
	if (rw & REQ_SYNC)
	rwstat->cnt[BLKG_RWSTAT_SYNC] += val;
	else
	rwstat->cnt[BLKG_RWSTAT_ASYNC] += val;

	u64_stats_update_end(&rwstat->syncp);
	}

	/**
	* blkg_rwstat_read - read the current values of a blkg_rwstat
	* @rwstat: blkg_rwstat to read
	*
	* Read the current snapshot of @rwstat and return it as the return value.
	* This function can be called without synchronization and takes care of
	* u64 atomicity.
	*/
	static struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)
	{
	unsigned int start;
	struct blkg_rwstat tmp;

	do {
	start = u64_stats_fetch_begin(&rwstat->syncp);
	tmp = *rwstat;
	} while (u64_stats_fetch_retry(&rwstat->syncp, start));

	return tmp;
	}

	/**
	* blkg_rwstat_sum - read the total count of a blkg_rwstat
	* @rwstat: blkg_rwstat to read
	*
	* Return the total count of @rwstat regardless of the IO direction. This
	* function can be called without synchronization and takes care of u64
	* atomicity.
	*/
	static inline uint64_t blkg_rwstat_sum(struct blkg_rwstat *rwstat)
	{
	struct blkg_rwstat tmp = blkg_rwstat_read(rwstat);

	return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE];
	}

	/**
	* blkg_rwstat_reset - reset a blkg_rwstat
	* @rwstat: blkg_rwstat to reset
	*/
	static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat)
	{
	memset(rwstat->cnt, 0, sizeof(rwstat->cnt));
	}

	#else

	struct blkio_group {
	};

	struct blkio_policy_type {
	};

	static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
	static inline void blkcg_drain_queue(struct request_queue *q) { }
	static inline void blkcg_exit_queue(struct request_queue *q) { }
	static inline void blkio_policy_register(struct blkio_policy_type *blkiop) { }
	static inline void blkio_policy_unregister(struct blkio_policy_type *blkiop) { }
	static inline void blkg_destroy_all(struct request_queue *q,
	bool destory_root) { }
	static inline void update_root_blkg_pd(struct request_queue *q,
	enum blkio_policy_id plid) { }

	static inline void blkg_to_pdata(struct blkio_group blkg,
	struct blkio_policy_type *pol) { return NULL; }
	static inline struct blkio_group pdata_to_blkg(void pdata,
	struct blkio_policy_type *pol) { return NULL; }
	static inline char blkg_path(struct blkio_group blkg) { return NULL; }
	static inline void blkg_get(struct blkio_group *blkg) { }
	static inline void blkg_put(struct blkio_group *blkg) { }

	#endif

	#ifdef CONFIG_BLK_CGROUP
	extern struct blkio_cgroup blkio_root_cgroup;
	extern struct blkio_cgroup cgroup_to_blkio_cgroup(struct cgroup cgroup);
	extern struct blkio_cgroup bio_blkio_cgroup(struct bio bio);
	extern struct blkio_group blkg_lookup(struct blkio_cgroup blkcg,
	struct request_queue *q);
	struct blkio_group blkg_lookup_create(struct blkio_cgroup blkcg,
	struct request_queue *q,
	bool for_root);
	#else
	struct cgroup;
	static inline struct blkio_cgroup *
	cgroup_to_blkio_cgroup(struct cgroup *cgroup) { return NULL; }
	static inline struct blkio_cgroup *
	bio_blkio_cgroup(struct bio *bio) { return NULL; }

	static inline struct blkio_group blkg_lookup(struct blkio_cgroup blkcg,
	void *key) { return NULL; }
	#endif
	#endif /* _BLK_CGROUP_H */