[thirdparty/linux.git] / include / linux / backing-dev-defs.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_BACKING_DEV_DEFS_H
#define __LINUX_BACKING_DEV_DEFS_H

#include <linux/list.h>
#include <linux/radix-tree.h>
#include <linux/rbtree.h>
#include <linux/spinlock.h>
#include <linux/percpu_counter.h>
#include <linux/percpu-refcount.h>
#include <linux/flex_proportions.h>
#include <linux/timer.h>
#include <linux/workqueue.h>
#include <linux/kref.h>
#include <linux/refcount.h>

struct page;
struct device;
struct dentry;

/*
 * Bits in bdi_writeback.state
 */
enum wb_state {
	WB_registered,		/* bdi_register() was done */
	WB_writeback_running,	/* Writeback is in progress */
	WB_has_dirty_io,	/* Dirty inodes on ->b_{dirty|io|more_io} */
	WB_start_all,		/* nr_pages == 0 (all) work pending */
};

enum wb_congested_state {
	WB_async_congested,	/* The async (write) queue is getting full */
	WB_sync_congested,	/* The sync queue is getting full */
};

typedef int (congested_fn)(void *, int);

enum wb_stat_item {
	WB_RECLAIMABLE,
	WB_WRITEBACK,
	WB_DIRTIED,
	WB_WRITTEN,
	NR_WB_STAT_ITEMS
};

#define WB_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))

/*
 * why some writeback work was initiated
 */
enum wb_reason {
	WB_REASON_BACKGROUND,
	WB_REASON_VMSCAN,
	WB_REASON_SYNC,
	WB_REASON_PERIODIC,
	WB_REASON_LAPTOP_TIMER,
	WB_REASON_FS_FREE_SPACE,
	/*
	 * There is no bdi forker thread any more and works are done
	 * by emergency worker, however, this is TPs userland visible
	 * and we'll be exposing exactly the same information,
	 * so it has a mismatch name.
	 */
	WB_REASON_FORKER_THREAD,
	WB_REASON_FOREIGN_FLUSH,

	WB_REASON_MAX,
};

struct wb_completion {
	atomic_t		cnt;
	wait_queue_head_t	*waitq;
};

#define __WB_COMPLETION_INIT(_waitq)	\
	(struct wb_completion){ .cnt = ATOMIC_INIT(1), .waitq = (_waitq) }

/*
 * If one wants to wait for one or more wb_writeback_works, each work's
 * ->done should be set to a wb_completion defined using the following
 * macro.  Once all work items are issued with wb_queue_work(), the caller
 * can wait for the completion of all using wb_wait_for_completion().  Work
 * items which are waited upon aren't freed automatically on completion.
 */
#define WB_COMPLETION_INIT(bdi)		__WB_COMPLETION_INIT(&(bdi)->wb_waitq)

#define DEFINE_WB_COMPLETION(cmpl, bdi)	\
	struct wb_completion cmpl = WB_COMPLETION_INIT(bdi)

/*
 * For cgroup writeback, multiple wb's may map to the same blkcg.  Those
 * wb's can operate mostly independently but should share the congested
 * state.  To facilitate such sharing, the congested state is tracked using
 * the following struct which is created on demand, indexed by blkcg ID on
 * its bdi, and refcounted.
 */
struct bdi_writeback_congested {
	unsigned long state;		/* WB_[a]sync_congested flags */
	refcount_t refcnt;		/* nr of attached wb's and blkg */

#ifdef CONFIG_CGROUP_WRITEBACK
	struct backing_dev_info *__bdi;	/* the associated bdi, set to NULL
					 * on bdi unregistration. For memcg-wb
					 * internal use only! */
	int blkcg_id;			/* ID of the associated blkcg */
	struct rb_node rb_node;		/* on bdi->cgwb_congestion_tree */
#endif
};

/*
 * Each wb (bdi_writeback) can perform writeback operations, is measured
 * and throttled, independently.  Without cgroup writeback, each bdi
 * (bdi_writeback) is served by its embedded bdi->wb.
 *
 * On the default hierarchy, blkcg implicitly enables memcg.  This allows
 * using memcg's page ownership for attributing writeback IOs, and every
 * memcg - blkcg combination can be served by its own wb by assigning a
 * dedicated wb to each memcg, which enables isolation across different
 * cgroups and propagation of IO back pressure down from the IO layer upto
 * the tasks which are generating the dirty pages to be written back.
 *
 * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
 * refcounted with the number of inodes attached to it, and pins the memcg
 * and the corresponding blkcg.  As the corresponding blkcg for a memcg may
 * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
 * is tested for blkcg after lookup and removed from index on mismatch so
 * that a new wb for the combination can be created.
 */
struct bdi_writeback {
	struct backing_dev_info *bdi;	/* our parent bdi */

	unsigned long state;		/* Always use atomic bitops on this */
	unsigned long last_old_flush;	/* last old data flush */

	struct list_head b_dirty;	/* dirty inodes */
	struct list_head b_io;		/* parked for writeback */
	struct list_head b_more_io;	/* parked for more writeback */
	struct list_head b_dirty_time;	/* time stamps are dirty */
	spinlock_t list_lock;		/* protects the b_* lists */

	struct percpu_counter stat[NR_WB_STAT_ITEMS];

	struct bdi_writeback_congested *congested;

	unsigned long bw_time_stamp;	/* last time write bw is updated */
	unsigned long dirtied_stamp;
	unsigned long written_stamp;	/* pages written at bw_time_stamp */
	unsigned long write_bandwidth;	/* the estimated write bandwidth */
	unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */

	/*
	 * The base dirty throttle rate, re-calculated on every 200ms.
	 * All the bdi tasks' dirty rate will be curbed under it.
	 * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
	 * in small steps and is much more smooth/stable than the latter.
	 */
	unsigned long dirty_ratelimit;
	unsigned long balanced_dirty_ratelimit;

	struct fprop_local_percpu completions;
	int dirty_exceeded;
	enum wb_reason start_all_reason;

	spinlock_t work_lock;		/* protects work_list & dwork scheduling */
	struct list_head work_list;
	struct delayed_work dwork;	/* work item used for writeback */

	unsigned long dirty_sleep;	/* last wait */

	struct list_head bdi_node;	/* anchored at bdi->wb_list */

#ifdef CONFIG_CGROUP_WRITEBACK
	struct percpu_ref refcnt;	/* used only for !root wb's */
	struct fprop_local_percpu memcg_completions;
	struct cgroup_subsys_state *memcg_css; /* the associated memcg */
	struct cgroup_subsys_state *blkcg_css; /* and blkcg */
	struct list_head memcg_node;	/* anchored at memcg->cgwb_list */
	struct list_head blkcg_node;	/* anchored at blkcg->cgwb_list */

	union {
		struct work_struct release_work;
		struct rcu_head rcu;
	};
#endif
};

struct backing_dev_info {
	u64 id;
	struct rb_node rb_node; /* keyed by ->id */
	struct list_head bdi_list;
	unsigned long ra_pages;	/* max readahead in PAGE_SIZE units */
	unsigned long io_pages;	/* max allowed IO size */
	congested_fn *congested_fn; /* Function pointer if device is md/dm */
	void *congested_data;	/* Pointer to aux data for congested func */

	const char *name;

	struct kref refcnt;	/* Reference counter for the structure */
	unsigned int capabilities; /* Device capabilities */
	unsigned int min_ratio;
	unsigned int max_ratio, max_prop_frac;

	/*
	 * Sum of avg_write_bw of wbs with dirty inodes.  > 0 if there are
	 * any dirty wbs, which is depended upon by bdi_has_dirty().
	 */
	atomic_long_t tot_write_bandwidth;

	struct bdi_writeback wb;  /* the root writeback info for this bdi */
	struct list_head wb_list; /* list of all wbs */
#ifdef CONFIG_CGROUP_WRITEBACK
	struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
	struct rb_root cgwb_congested_tree; /* their congested states */
	struct mutex cgwb_release_mutex;  /* protect shutdown of wb structs */
	struct rw_semaphore wb_switch_rwsem; /* no cgwb switch while syncing */
#else
	struct bdi_writeback_congested *wb_congested;
#endif
	wait_queue_head_t wb_waitq;

	struct device *dev;
	char dev_name[64];
	struct device *owner;

	struct timer_list laptop_mode_wb_timer;

#ifdef CONFIG_DEBUG_FS
	struct dentry *debug_dir;
#endif
};

enum {
	BLK_RW_ASYNC	= 0,
	BLK_RW_SYNC	= 1,
};

void clear_wb_congested(struct bdi_writeback_congested *congested, int sync);
void set_wb_congested(struct bdi_writeback_congested *congested, int sync);

static inline void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
{
	clear_wb_congested(bdi->wb.congested, sync);
}

static inline void set_bdi_congested(struct backing_dev_info *bdi, int sync)
{
	set_wb_congested(bdi->wb.congested, sync);
}

struct wb_lock_cookie {
	bool locked;
	unsigned long flags;
};

#ifdef CONFIG_CGROUP_WRITEBACK

/**
 * wb_tryget - try to increment a wb's refcount
 * @wb: bdi_writeback to get
 */
static inline bool wb_tryget(struct bdi_writeback *wb)
{
	if (wb != &wb->bdi->wb)
		return percpu_ref_tryget(&wb->refcnt);
	return true;
}

/**
 * wb_get - increment a wb's refcount
 * @wb: bdi_writeback to get
 */
static inline void wb_get(struct bdi_writeback *wb)
{
	if (wb != &wb->bdi->wb)
		percpu_ref_get(&wb->refcnt);
}

/**
 * wb_put - decrement a wb's refcount
 * @wb: bdi_writeback to put
 */
static inline void wb_put(struct bdi_writeback *wb)
{
	if (WARN_ON_ONCE(!wb->bdi)) {
		/*
		 * A driver bug might cause a file to be removed before bdi was
		 * initialized.
		 */
		return;
	}

	if (wb != &wb->bdi->wb)
		percpu_ref_put(&wb->refcnt);
}

/**
 * wb_dying - is a wb dying?
 * @wb: bdi_writeback of interest
 *
 * Returns whether @wb is unlinked and being drained.
 */
static inline bool wb_dying(struct bdi_writeback *wb)
{
	return percpu_ref_is_dying(&wb->refcnt);
}

#else	/* CONFIG_CGROUP_WRITEBACK */

static inline bool wb_tryget(struct bdi_writeback *wb)
{
	return true;
}

static inline void wb_get(struct bdi_writeback *wb)
{
}

static inline void wb_put(struct bdi_writeback *wb)
{
}

static inline bool wb_dying(struct bdi_writeback *wb)
{
	return false;
}

#endif	/* CONFIG_CGROUP_WRITEBACK */

#endif	/* __LINUX_BACKING_DEV_DEFS_H */
Commit	Line	Data
b2441318	1	/* SPDX-License-Identifier: GPL-2.0 */
66114cad TH	2	#ifndef __LINUX_BACKING_DEV_DEFS_H
	3	#define __LINUX_BACKING_DEV_DEFS_H
	4
	5	#include <linux/list.h>
52ebea74 TH	6	#include <linux/radix-tree.h>
52ebea74 TH	7	#include <linux/rbtree.h>
66114cad TH	8	#include <linux/spinlock.h>
66114cad TH	9	#include <linux/percpu_counter.h>
52ebea74	10	#include <linux/percpu-refcount.h>
66114cad TH	11	#include <linux/flex_proportions.h>
	12	#include <linux/timer.h>
	13	#include <linux/workqueue.h>
d03f6cdc	14	#include <linux/kref.h>
e58dd0de	15	#include <linux/refcount.h>
66114cad TH	16
	17	struct page;
	18	struct device;
	19	struct dentry;
	20
	21	/*
	22	* Bits in bdi_writeback.state
	23	*/
	24	enum wb_state {
66114cad TH	25	WB_registered, /* bdi_register() was done */
66114cad TH	26	WB_writeback_running, /* Writeback is in progress */
d6c10f1f	27	WB_has_dirty_io, /* Dirty inodes on ->b_{dirty\|io\|more_io} */
aac8d41c	28	WB_start_all, /* nr_pages == 0 (all) work pending */
66114cad TH	29	};
66114cad TH	30
4aa9c692 TH	31	enum wb_congested_state {
	32	WB_async_congested, /* The async (write) queue is getting full */
	33	WB_sync_congested, /* The sync queue is getting full */
	34	};
	35
66114cad TH	36	typedef int (congested_fn)(void *, int);
	37
	38	enum wb_stat_item {
	39	WB_RECLAIMABLE,
	40	WB_WRITEBACK,
	41	WB_DIRTIED,
	42	WB_WRITTEN,
	43	NR_WB_STAT_ITEMS
	44	};
	45
	46	#define WB_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
	47
85009b4f JA	48	/*
	49	* why some writeback work was initiated
	50	*/
	51	enum wb_reason {
	52	WB_REASON_BACKGROUND,
	53	WB_REASON_VMSCAN,
	54	WB_REASON_SYNC,
	55	WB_REASON_PERIODIC,
	56	WB_REASON_LAPTOP_TIMER,
85009b4f JA	57	WB_REASON_FS_FREE_SPACE,
	58	/*
	59	* There is no bdi forker thread any more and works are done
	60	* by emergency worker, however, this is TPs userland visible
	61	* and we'll be exposing exactly the same information,
	62	* so it has a mismatch name.
	63	*/
	64	WB_REASON_FORKER_THREAD,
97b27821	65	WB_REASON_FOREIGN_FLUSH,
85009b4f JA	66
	67	WB_REASON_MAX,
	68	};
	69
5b9cce4c TH	70	struct wb_completion {
	71	atomic_t cnt;
	72	wait_queue_head_t *waitq;
	73	};
	74
	75	#define __WB_COMPLETION_INIT(_waitq) \
	76	(struct wb_completion){ .cnt = ATOMIC_INIT(1), .waitq = (_waitq) }
	77
	78	/*
	79	* If one wants to wait for one or more wb_writeback_works, each work's
	80	* ->done should be set to a wb_completion defined using the following
	81	* macro. Once all work items are issued with wb_queue_work(), the caller
	82	* can wait for the completion of all using wb_wait_for_completion(). Work
	83	* items which are waited upon aren't freed automatically on completion.
	84	*/
	85	#define WB_COMPLETION_INIT(bdi) __WB_COMPLETION_INIT(&(bdi)->wb_waitq)
	86
	87	#define DEFINE_WB_COMPLETION(cmpl, bdi) \
	88	struct wb_completion cmpl = WB_COMPLETION_INIT(bdi)
	89
52ebea74 TH	90	/*
	91	* For cgroup writeback, multiple wb's may map to the same blkcg. Those
	92	* wb's can operate mostly independently but should share the congested
	93	* state. To facilitate such sharing, the congested state is tracked using
	94	* the following struct which is created on demand, indexed by blkcg ID on
	95	* its bdi, and refcounted.
	96	*/
4aa9c692 TH	97	struct bdi_writeback_congested {
4aa9c692 TH	98	unsigned long state; /* WB_[a]sync_congested flags */
e58dd0de	99	refcount_t refcnt; /* nr of attached wb's and blkg */
52ebea74 TH	100
52ebea74 TH	101	#ifdef CONFIG_CGROUP_WRITEBACK
b7d680d7 JK	102	struct backing_dev_info __bdi; / the associated bdi, set to NULL
	103	* on bdi unregistration. For memcg-wb
	104	* internal use only! */
52ebea74 TH	105	int blkcg_id; /* ID of the associated blkcg */
	106	struct rb_node rb_node; /* on bdi->cgwb_congestion_tree */
	107	#endif
4aa9c692 TH	108	};
4aa9c692 TH	109
52ebea74 TH	110	/*
	111	* Each wb (bdi_writeback) can perform writeback operations, is measured
	112	* and throttled, independently. Without cgroup writeback, each bdi
	113	* (bdi_writeback) is served by its embedded bdi->wb.
	114	*
	115	* On the default hierarchy, blkcg implicitly enables memcg. This allows
	116	* using memcg's page ownership for attributing writeback IOs, and every
	117	* memcg - blkcg combination can be served by its own wb by assigning a
	118	* dedicated wb to each memcg, which enables isolation across different
	119	* cgroups and propagation of IO back pressure down from the IO layer upto
	120	* the tasks which are generating the dirty pages to be written back.
	121	*
	122	* A cgroup wb is indexed on its bdi by the ID of the associated memcg,
	123	* refcounted with the number of inodes attached to it, and pins the memcg
	124	* and the corresponding blkcg. As the corresponding blkcg for a memcg may
	125	* change as blkcg is disabled and enabled higher up in the hierarchy, a wb
	126	* is tested for blkcg after lookup and removed from index on mismatch so
	127	* that a new wb for the combination can be created.
	128	*/
66114cad TH	129	struct bdi_writeback {
	130	struct backing_dev_info bdi; / our parent bdi */
	131
	132	unsigned long state; /* Always use atomic bitops on this */
	133	unsigned long last_old_flush; /* last old data flush */
	134
	135	struct list_head b_dirty; /* dirty inodes */
	136	struct list_head b_io; /* parked for writeback */
	137	struct list_head b_more_io; /* parked for more writeback */
	138	struct list_head b_dirty_time; /* time stamps are dirty */
	139	spinlock_t list_lock; /* protects the b_* lists */
	140
	141	struct percpu_counter stat[NR_WB_STAT_ITEMS];
	142
4aa9c692 TH	143	struct bdi_writeback_congested *congested;
4aa9c692 TH	144
66114cad TH	145	unsigned long bw_time_stamp; /* last time write bw is updated */
	146	unsigned long dirtied_stamp;
	147	unsigned long written_stamp; /* pages written at bw_time_stamp */
	148	unsigned long write_bandwidth; /* the estimated write bandwidth */
95a46c65	149	unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */
66114cad TH	150
	151	/*
	152	* The base dirty throttle rate, re-calculated on every 200ms.
	153	* All the bdi tasks' dirty rate will be curbed under it.
	154	* @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
	155	* in small steps and is much more smooth/stable than the latter.
	156	*/
	157	unsigned long dirty_ratelimit;
	158	unsigned long balanced_dirty_ratelimit;
	159
	160	struct fprop_local_percpu completions;
	161	int dirty_exceeded;
85009b4f	162	enum wb_reason start_all_reason;
66114cad TH	163
	164	spinlock_t work_lock; /* protects work_list & dwork scheduling */
	165	struct list_head work_list;
	166	struct delayed_work dwork; /* work item used for writeback */
52ebea74	167
b57d74af JA	168	unsigned long dirty_sleep; /* last wait */
b57d74af JA	169
b817525a TH	170	struct list_head bdi_node; /* anchored at bdi->wb_list */
b817525a TH	171
52ebea74 TH	172	#ifdef CONFIG_CGROUP_WRITEBACK
52ebea74 TH	173	struct percpu_ref refcnt; /* used only for !root wb's */
841710aa	174	struct fprop_local_percpu memcg_completions;
52ebea74 TH	175	struct cgroup_subsys_state memcg_css; / the associated memcg */
	176	struct cgroup_subsys_state blkcg_css; / and blkcg */
	177	struct list_head memcg_node; /* anchored at memcg->cgwb_list */
	178	struct list_head blkcg_node; /* anchored at blkcg->cgwb_list */
	179
	180	union {
	181	struct work_struct release_work;
	182	struct rcu_head rcu;
	183	};
	184	#endif
66114cad TH	185	};
	186
	187	struct backing_dev_info {
34f8fe50 TH	188	u64 id;
34f8fe50 TH	189	struct rb_node rb_node; /* keyed by ->id */
66114cad	190	struct list_head bdi_list;
ea1754a0	191	unsigned long ra_pages; /* max readahead in PAGE_SIZE units */
9491ae4a	192	unsigned long io_pages; /* max allowed IO size */
66114cad TH	193	congested_fn congested_fn; / Function pointer if device is md/dm */
	194	void congested_data; / Pointer to aux data for congested func */
	195
fca39346	196	const char *name;
66114cad	197
d03f6cdc	198	struct kref refcnt; /* Reference counter for the structure */
8db378a5	199	unsigned int capabilities; /* Device capabilities */
66114cad TH	200	unsigned int min_ratio;
	201	unsigned int max_ratio, max_prop_frac;
	202
95a46c65 TH	203	/*
	204	* Sum of avg_write_bw of wbs with dirty inodes. > 0 if there are
	205	* any dirty wbs, which is depended upon by bdi_has_dirty().
	206	*/
	207	atomic_long_t tot_write_bandwidth;
766a9d6e	208
52ebea74	209	struct bdi_writeback wb; /* the root writeback info for this bdi */
b817525a	210	struct list_head wb_list; /* list of all wbs */
52ebea74 TH	211	#ifdef CONFIG_CGROUP_WRITEBACK
	212	struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
	213	struct rb_root cgwb_congested_tree; /* their congested states */
3ee7e869	214	struct mutex cgwb_release_mutex; /* protect shutdown of wb structs */
7fc5854f	215	struct rw_semaphore wb_switch_rwsem; /* no cgwb switch while syncing */
a13f35e8 TH	216	#else
a13f35e8 TH	217	struct bdi_writeback_congested *wb_congested;
52ebea74	218	#endif
cc395d7f TH	219	wait_queue_head_t wb_waitq;
cc395d7f TH	220
66114cad	221	struct device *dev;
6bd87eec	222	char dev_name[64];
df08c32c	223	struct device *owner;
66114cad TH	224
	225	struct timer_list laptop_mode_wb_timer;
	226
	227	#ifdef CONFIG_DEBUG_FS
	228	struct dentry *debug_dir;
66114cad TH	229	#endif
	230	};
	231
	232	enum {
	233	BLK_RW_ASYNC = 0,
	234	BLK_RW_SYNC = 1,
	235	};
	236
ec8a6f26 TH	237	void clear_wb_congested(struct bdi_writeback_congested *congested, int sync);
	238	void set_wb_congested(struct bdi_writeback_congested *congested, int sync);
	239
	240	static inline void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
	241	{
	242	clear_wb_congested(bdi->wb.congested, sync);
	243	}
	244
	245	static inline void set_bdi_congested(struct backing_dev_info *bdi, int sync)
	246	{
	247	set_wb_congested(bdi->wb.congested, sync);
	248	}
66114cad	249
2e898e4c GT	250	struct wb_lock_cookie {
	251	bool locked;
	252	unsigned long flags;
	253	};
	254
21c6321f TH	255	#ifdef CONFIG_CGROUP_WRITEBACK
	256
	257	/**
	258	* wb_tryget - try to increment a wb's refcount
	259	* @wb: bdi_writeback to get
	260	*/
	261	static inline bool wb_tryget(struct bdi_writeback *wb)
	262	{
	263	if (wb != &wb->bdi->wb)
	264	return percpu_ref_tryget(&wb->refcnt);
	265	return true;
	266	}
	267
	268	/**
	269	* wb_get - increment a wb's refcount
	270	* @wb: bdi_writeback to get
	271	*/
	272	static inline void wb_get(struct bdi_writeback *wb)
	273	{
	274	if (wb != &wb->bdi->wb)
	275	percpu_ref_get(&wb->refcnt);
	276	}
	277
	278	/**
	279	* wb_put - decrement a wb's refcount
	280	* @wb: bdi_writeback to put
	281	*/
	282	static inline void wb_put(struct bdi_writeback *wb)
	283	{
368686a9 AR	284	if (WARN_ON_ONCE(!wb->bdi)) {
	285	/*
	286	* A driver bug might cause a file to be removed before bdi was
	287	* initialized.
	288	*/
	289	return;
	290	}
	291
21c6321f TH	292	if (wb != &wb->bdi->wb)
	293	percpu_ref_put(&wb->refcnt);
	294	}
	295
e8a7abf5 TH	296	/**
	297	* wb_dying - is a wb dying?
	298	* @wb: bdi_writeback of interest
	299	*
	300	* Returns whether @wb is unlinked and being drained.
	301	*/
	302	static inline bool wb_dying(struct bdi_writeback *wb)
	303	{
	304	return percpu_ref_is_dying(&wb->refcnt);
	305	}
	306
21c6321f TH	307	#else /* CONFIG_CGROUP_WRITEBACK */
	308
	309	static inline bool wb_tryget(struct bdi_writeback *wb)
	310	{
	311	return true;
	312	}
	313
	314	static inline void wb_get(struct bdi_writeback *wb)
	315	{
	316	}
	317
	318	static inline void wb_put(struct bdi_writeback *wb)
	319	{
	320	}
	321
e8a7abf5 TH	322	static inline bool wb_dying(struct bdi_writeback *wb)
	323	{
	324	return false;
	325	}
	326
21c6321f TH	327	#endif /* CONFIG_CGROUP_WRITEBACK */
21c6321f TH	328
66114cad	329	#endif /* __LINUX_BACKING_DEV_DEFS_H */