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
36typedef int (congested_fn)(void *, int);
37
38enum 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
48/*
49 * why some writeback work was initiated
50 */
51enum wb_reason {
52 WB_REASON_BACKGROUND,
53 WB_REASON_VMSCAN,
54 WB_REASON_SYNC,
55 WB_REASON_PERIODIC,
56 WB_REASON_LAPTOP_TIMER,
57 WB_REASON_FREE_MORE_MEM,
58 WB_REASON_FS_FREE_SPACE,
59 /*
60 * There is no bdi forker thread any more and works are done
61 * by emergency worker, however, this is TPs userland visible
62 * and we'll be exposing exactly the same information,
63 * so it has a mismatch name.
64 */
65 WB_REASON_FORKER_THREAD,
66
67 WB_REASON_MAX,
68};
69
70/*
71 * For cgroup writeback, multiple wb's may map to the same blkcg. Those
72 * wb's can operate mostly independently but should share the congested
73 * state. To facilitate such sharing, the congested state is tracked using
74 * the following struct which is created on demand, indexed by blkcg ID on
75 * its bdi, and refcounted.
76 */
77struct bdi_writeback_congested {
78 unsigned long state; /* WB_[a]sync_congested flags */
79 refcount_t refcnt; /* nr of attached wb's and blkg */
80
81#ifdef CONFIG_CGROUP_WRITEBACK
82 struct backing_dev_info *__bdi; /* the associated bdi, set to NULL
83 * on bdi unregistration. For memcg-wb
84 * internal use only! */
85 int blkcg_id; /* ID of the associated blkcg */
86 struct rb_node rb_node; /* on bdi->cgwb_congestion_tree */
87#endif
88};
89
90/*
91 * Each wb (bdi_writeback) can perform writeback operations, is measured
92 * and throttled, independently. Without cgroup writeback, each bdi
93 * (bdi_writeback) is served by its embedded bdi->wb.
94 *
95 * On the default hierarchy, blkcg implicitly enables memcg. This allows
96 * using memcg's page ownership for attributing writeback IOs, and every
97 * memcg - blkcg combination can be served by its own wb by assigning a
98 * dedicated wb to each memcg, which enables isolation across different
99 * cgroups and propagation of IO back pressure down from the IO layer upto
100 * the tasks which are generating the dirty pages to be written back.
101 *
102 * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
103 * refcounted with the number of inodes attached to it, and pins the memcg
104 * and the corresponding blkcg. As the corresponding blkcg for a memcg may
105 * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
106 * is tested for blkcg after lookup and removed from index on mismatch so
107 * that a new wb for the combination can be created.
108 */
109struct bdi_writeback {
110 struct backing_dev_info *bdi; /* our parent bdi */
111
112 unsigned long state; /* Always use atomic bitops on this */
113 unsigned long last_old_flush; /* last old data flush */
114
115 struct list_head b_dirty; /* dirty inodes */
116 struct list_head b_io; /* parked for writeback */
117 struct list_head b_more_io; /* parked for more writeback */
118 struct list_head b_dirty_time; /* time stamps are dirty */
119 spinlock_t list_lock; /* protects the b_* lists */
120
121 struct percpu_counter stat[NR_WB_STAT_ITEMS];
122
123 struct bdi_writeback_congested *congested;
124
125 unsigned long bw_time_stamp; /* last time write bw is updated */
126 unsigned long dirtied_stamp;
127 unsigned long written_stamp; /* pages written at bw_time_stamp */
128 unsigned long write_bandwidth; /* the estimated write bandwidth */
129 unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */
130
131 /*
132 * The base dirty throttle rate, re-calculated on every 200ms.
133 * All the bdi tasks' dirty rate will be curbed under it.
134 * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
135 * in small steps and is much more smooth/stable than the latter.
136 */
137 unsigned long dirty_ratelimit;
138 unsigned long balanced_dirty_ratelimit;
139
140 struct fprop_local_percpu completions;
141 int dirty_exceeded;
142 enum wb_reason start_all_reason;
143
144 spinlock_t work_lock; /* protects work_list & dwork scheduling */
145 struct list_head work_list;
146 struct delayed_work dwork; /* work item used for writeback */
147
148 unsigned long dirty_sleep; /* last wait */
149
150 struct list_head bdi_node; /* anchored at bdi->wb_list */
151
152#ifdef CONFIG_CGROUP_WRITEBACK
153 struct percpu_ref refcnt; /* used only for !root wb's */
154 struct fprop_local_percpu memcg_completions;
155 struct cgroup_subsys_state *memcg_css; /* the associated memcg */
156 struct cgroup_subsys_state *blkcg_css; /* and blkcg */
157 struct list_head memcg_node; /* anchored at memcg->cgwb_list */
158 struct list_head blkcg_node; /* anchored at blkcg->cgwb_list */
159
160 union {
161 struct work_struct release_work;
162 struct rcu_head rcu;
163 };
164#endif
165};
166
167struct backing_dev_info {
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 congested_fn *congested_fn; /* Function pointer if device is md/dm */
172 void *congested_data; /* Pointer to aux data for congested func */
173
174 const char *name;
175
176 struct kref refcnt; /* Reference counter for the structure */
177 unsigned int capabilities; /* Device capabilities */
178 unsigned int min_ratio;
179 unsigned int max_ratio, max_prop_frac;
180
181 /*
182 * Sum of avg_write_bw of wbs with dirty inodes. > 0 if there are
183 * any dirty wbs, which is depended upon by bdi_has_dirty().
184 */
185 atomic_long_t tot_write_bandwidth;
186
187 struct bdi_writeback wb; /* the root writeback info for this bdi */
188 struct list_head wb_list; /* list of all wbs */
189#ifdef CONFIG_CGROUP_WRITEBACK
190 struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
191 struct rb_root cgwb_congested_tree; /* their congested states */
192 struct mutex cgwb_release_mutex; /* protect shutdown of wb structs */
193 struct rw_semaphore wb_switch_rwsem; /* no cgwb switch while syncing */
194#else
195 struct bdi_writeback_congested *wb_congested;
196#endif
197 wait_queue_head_t wb_waitq;
198
199 struct device *dev;
200 struct device *owner;
201
202 struct timer_list laptop_mode_wb_timer;
203
204#ifdef CONFIG_DEBUG_FS
205 struct dentry *debug_dir;
206 struct dentry *debug_stats;
207#endif
208};
209
210enum {
211 BLK_RW_ASYNC = 0,
212 BLK_RW_SYNC = 1,
213};
214
215void clear_wb_congested(struct bdi_writeback_congested *congested, int sync);
216void set_wb_congested(struct bdi_writeback_congested *congested, int sync);
217
218static inline void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
219{
220 clear_wb_congested(bdi->wb.congested, sync);
221}
222
223static inline void set_bdi_congested(struct backing_dev_info *bdi, int sync)
224{
225 set_wb_congested(bdi->wb.congested, sync);
226}
227
228struct wb_lock_cookie {
229 bool locked;
230 unsigned long flags;
231};
232
233#ifdef CONFIG_CGROUP_WRITEBACK
234
235/**
236 * wb_tryget - try to increment a wb's refcount
237 * @wb: bdi_writeback to get
238 */
239static inline bool wb_tryget(struct bdi_writeback *wb)
240{
241 if (wb != &wb->bdi->wb)
242 return percpu_ref_tryget(&wb->refcnt);
243 return true;
244}
245
246/**
247 * wb_get - increment a wb's refcount
248 * @wb: bdi_writeback to get
249 */
250static inline void wb_get(struct bdi_writeback *wb)
251{
252 if (wb != &wb->bdi->wb)
253 percpu_ref_get(&wb->refcnt);
254}
255
256/**
257 * wb_put - decrement a wb's refcount
258 * @wb: bdi_writeback to put
259 */
260static inline void wb_put(struct bdi_writeback *wb)
261{
262 if (WARN_ON_ONCE(!wb->bdi)) {
263 /*
264 * A driver bug might cause a file to be removed before bdi was
265 * initialized.
266 */
267 return;
268 }
269
270 if (wb != &wb->bdi->wb)
271 percpu_ref_put(&wb->refcnt);
272}
273
274/**
275 * wb_dying - is a wb dying?
276 * @wb: bdi_writeback of interest
277 *
278 * Returns whether @wb is unlinked and being drained.
279 */
280static inline bool wb_dying(struct bdi_writeback *wb)
281{
282 return percpu_ref_is_dying(&wb->refcnt);
283}
284
285#else /* CONFIG_CGROUP_WRITEBACK */
286
287static inline bool wb_tryget(struct bdi_writeback *wb)
288{
289 return true;
290}
291
292static inline void wb_get(struct bdi_writeback *wb)
293{
294}
295
296static inline void wb_put(struct bdi_writeback *wb)
297{
298}
299
300static inline bool wb_dying(struct bdi_writeback *wb)
301{
302 return false;
303}
304
305#endif /* CONFIG_CGROUP_WRITEBACK */
306
307#endif /* __LINUX_BACKING_DEV_DEFS_H */
308