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_stat_item {
32	WB_RECLAIMABLE,
33	WB_WRITEBACK,
34	WB_DIRTIED,
35	WB_WRITTEN,
36	NR_WB_STAT_ITEMS
37};
38
39#define WB_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
40
41/*
42 * why some writeback work was initiated
43 */
44enum wb_reason {
45	WB_REASON_BACKGROUND,
46	WB_REASON_VMSCAN,
47	WB_REASON_SYNC,
48	WB_REASON_PERIODIC,
49	WB_REASON_LAPTOP_TIMER,
50	WB_REASON_FS_FREE_SPACE,
51	/*
52	 * There is no bdi forker thread any more and works are done
53	 * by emergency worker, however, this is TPs userland visible
54	 * and we'll be exposing exactly the same information,
55	 * so it has a mismatch name.
56	 */
57	WB_REASON_FORKER_THREAD,
58	WB_REASON_FOREIGN_FLUSH,
59
60	WB_REASON_MAX,
61};
62
63struct wb_completion {
64	atomic_t		cnt;
65	wait_queue_head_t	*waitq;
66};
67
68#define __WB_COMPLETION_INIT(_waitq)	\
69	(struct wb_completion){ .cnt = ATOMIC_INIT(1), .waitq = (_waitq) }
70
71/*
72 * If one wants to wait for one or more wb_writeback_works, each work's
73 * ->done should be set to a wb_completion defined using the following
74 * macro.  Once all work items are issued with wb_queue_work(), the caller
75 * can wait for the completion of all using wb_wait_for_completion().  Work
76 * items which are waited upon aren't freed automatically on completion.
77 */
78#define WB_COMPLETION_INIT(bdi)		__WB_COMPLETION_INIT(&(bdi)->wb_waitq)
79
80#define DEFINE_WB_COMPLETION(cmpl, bdi)	\
81	struct wb_completion cmpl = WB_COMPLETION_INIT(bdi)
82
83/*
84 * Each wb (bdi_writeback) can perform writeback operations, is measured
85 * and throttled, independently.  Without cgroup writeback, each bdi
86 * (bdi_writeback) is served by its embedded bdi->wb.
87 *
88 * On the default hierarchy, blkcg implicitly enables memcg.  This allows
89 * using memcg's page ownership for attributing writeback IOs, and every
90 * memcg - blkcg combination can be served by its own wb by assigning a
91 * dedicated wb to each memcg, which enables isolation across different
92 * cgroups and propagation of IO back pressure down from the IO layer upto
93 * the tasks which are generating the dirty pages to be written back.
94 *
95 * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
96 * refcounted with the number of inodes attached to it, and pins the memcg
97 * and the corresponding blkcg.  As the corresponding blkcg for a memcg may
98 * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
99 * is tested for blkcg after lookup and removed from index on mismatch so
100 * that a new wb for the combination can be created.
101 *
102 * Each bdi_writeback that is not embedded into the backing_dev_info must hold
103 * a reference to the parent backing_dev_info.  See cgwb_create() for details.
104 */
105struct bdi_writeback {
106	struct backing_dev_info *bdi;	/* our parent bdi */
107
108	unsigned long state;		/* Always use atomic bitops on this */
109	unsigned long last_old_flush;	/* last old data flush */
110
111	struct list_head b_dirty;	/* dirty inodes */
112	struct list_head b_io;		/* parked for writeback */
113	struct list_head b_more_io;	/* parked for more writeback */
114	struct list_head b_dirty_time;	/* time stamps are dirty */
115	spinlock_t list_lock;		/* protects the b_* lists */
116
117	atomic_t writeback_inodes;	/* number of inodes under writeback */
118	struct percpu_counter stat[NR_WB_STAT_ITEMS];
119
120	unsigned long bw_time_stamp;	/* last time write bw is updated */
121	unsigned long dirtied_stamp;
122	unsigned long written_stamp;	/* pages written at bw_time_stamp */
123	unsigned long write_bandwidth;	/* the estimated write bandwidth */
124	unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */
125
126	/*
127	 * The base dirty throttle rate, re-calculated on every 200ms.
128	 * All the bdi tasks' dirty rate will be curbed under it.
129	 * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
130	 * in small steps and is much more smooth/stable than the latter.
131	 */
132	unsigned long dirty_ratelimit;
133	unsigned long balanced_dirty_ratelimit;
134
135	struct fprop_local_percpu completions;
136	int dirty_exceeded;
137	enum wb_reason start_all_reason;
138
139	spinlock_t work_lock;		/* protects work_list & dwork scheduling */
140	struct list_head work_list;
141	struct delayed_work dwork;	/* work item used for writeback */
142	struct delayed_work bw_dwork;	/* work item used for bandwidth estimate */
143
144	struct list_head bdi_node;	/* anchored at bdi->wb_list */
145
146#ifdef CONFIG_CGROUP_WRITEBACK
147	struct percpu_ref refcnt;	/* used only for !root wb's */
148	struct fprop_local_percpu memcg_completions;
149	struct cgroup_subsys_state *memcg_css; /* the associated memcg */
150	struct cgroup_subsys_state *blkcg_css; /* and blkcg */
151	struct list_head memcg_node;	/* anchored at memcg->cgwb_list */
152	struct list_head blkcg_node;	/* anchored at blkcg->cgwb_list */
153	struct list_head b_attached;	/* attached inodes, protected by list_lock */
154	struct list_head offline_node;	/* anchored at offline_cgwbs */
155
156	union {
157		struct work_struct release_work;
158		struct rcu_head rcu;
159	};
160#endif
161};
162
163struct backing_dev_info {
164	u64 id;
165	struct rb_node rb_node; /* keyed by ->id */
166	struct list_head bdi_list;
167	unsigned long ra_pages;	/* max readahead in PAGE_SIZE units */
168	unsigned long io_pages;	/* max allowed IO size */
169
170	struct kref refcnt;	/* Reference counter for the structure */
171	unsigned int capabilities; /* Device capabilities */
172	unsigned int min_ratio;
173	unsigned int max_ratio, max_prop_frac;
174
175	/*
176	 * Sum of avg_write_bw of wbs with dirty inodes.  > 0 if there are
177	 * any dirty wbs, which is depended upon by bdi_has_dirty().
178	 */
179	atomic_long_t tot_write_bandwidth;
180	/*
181	 * Jiffies when last process was dirty throttled on this bdi. Used by
182	 * blk-wbt.
183	 */
184	unsigned long last_bdp_sleep;
185
186	struct bdi_writeback wb;  /* the root writeback info for this bdi */
187	struct list_head wb_list; /* list of all wbs */
188#ifdef CONFIG_CGROUP_WRITEBACK
189	struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
190	struct mutex cgwb_release_mutex;  /* protect shutdown of wb structs */
191	struct rw_semaphore wb_switch_rwsem; /* no cgwb switch while syncing */
192#endif
193	wait_queue_head_t wb_waitq;
194
195	struct device *dev;
196	char dev_name[64];
197	struct device *owner;
198
199	struct timer_list laptop_mode_wb_timer;
200
201#ifdef CONFIG_DEBUG_FS
202	struct dentry *debug_dir;
203#endif
204};
205
206struct wb_lock_cookie {
207	bool locked;
208	unsigned long flags;
209};
210
211#ifdef CONFIG_CGROUP_WRITEBACK
212
213/**
214 * wb_tryget - try to increment a wb's refcount
215 * @wb: bdi_writeback to get
216 */
217static inline bool wb_tryget(struct bdi_writeback *wb)
218{
219	if (wb != &wb->bdi->wb)
220		return percpu_ref_tryget(&wb->refcnt);
221	return true;
222}
223
224/**
225 * wb_get - increment a wb's refcount
226 * @wb: bdi_writeback to get
227 */
228static inline void wb_get(struct bdi_writeback *wb)
229{
230	if (wb != &wb->bdi->wb)
231		percpu_ref_get(&wb->refcnt);
232}
233
234/**
235 * wb_put - decrement a wb's refcount
236 * @wb: bdi_writeback to put
237 * @nr: number of references to put
238 */
239static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)
240{
241	if (WARN_ON_ONCE(!wb->bdi)) {
242		/*
243		 * A driver bug might cause a file to be removed before bdi was
244		 * initialized.
245		 */
246		return;
247	}
248
249	if (wb != &wb->bdi->wb)
250		percpu_ref_put_many(&wb->refcnt, nr);
251}
252
253/**
254 * wb_put - decrement a wb's refcount
255 * @wb: bdi_writeback to put
256 */
257static inline void wb_put(struct bdi_writeback *wb)
258{
259	wb_put_many(wb, 1);
260}
261
262/**
263 * wb_dying - is a wb dying?
264 * @wb: bdi_writeback of interest
265 *
266 * Returns whether @wb is unlinked and being drained.
267 */
268static inline bool wb_dying(struct bdi_writeback *wb)
269{
270	return percpu_ref_is_dying(&wb->refcnt);
271}
272
273#else	/* CONFIG_CGROUP_WRITEBACK */
274
275static inline bool wb_tryget(struct bdi_writeback *wb)
276{
277	return true;
278}
279
280static inline void wb_get(struct bdi_writeback *wb)
281{
282}
283
284static inline void wb_put(struct bdi_writeback *wb)
285{
286}
287
288static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)
289{
290}
291
292static inline bool wb_dying(struct bdi_writeback *wb)
293{
294	return false;
295}
296
297#endif	/* CONFIG_CGROUP_WRITEBACK */
298
299#endif	/* __LINUX_BACKING_DEV_DEFS_H */
300