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