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 struct work_struct switch_work; /* work used to perform inode switching
156 * to this wb */
157 struct llist_head switch_wbs_ctxs; /* queued contexts for
158 * writeback switching */
159
160 union {
161 struct work_struct release_work;
162 struct rcu_head rcu;
163 };
164#endif
165};
166
167struct backing_dev_info {
168 u64 id;
169 struct rb_node rb_node; /* keyed by ->id */
170 struct list_head bdi_list;
171 unsigned long ra_pages; /* max readahead in PAGE_SIZE units */
172 unsigned long io_pages; /* max allowed IO size */
173
174 struct kref refcnt; /* Reference counter for the structure */
175 unsigned int capabilities; /* Device capabilities */
176 unsigned int min_ratio;
177 unsigned int max_ratio, max_prop_frac;
178
179 /*
180 * Sum of avg_write_bw of wbs with dirty inodes. > 0 if there are
181 * any dirty wbs, which is depended upon by bdi_has_dirty().
182 */
183 atomic_long_t tot_write_bandwidth;
184 /*
185 * Jiffies when last process was dirty throttled on this bdi. Used by
186 * blk-wbt.
187 */
188 unsigned long last_bdp_sleep;
189
190 struct bdi_writeback wb; /* the root writeback info for this bdi */
191 struct list_head wb_list; /* list of all wbs */
192#ifdef CONFIG_CGROUP_WRITEBACK
193 struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
194 struct mutex cgwb_release_mutex; /* protect shutdown of wb structs */
195 struct rw_semaphore wb_switch_rwsem; /* no cgwb switch while syncing */
196#endif
197 wait_queue_head_t wb_waitq;
198
199 struct device *dev;
200 char dev_name[64];
201 struct device *owner;
202
203 struct timer_list laptop_mode_wb_timer;
204
205#ifdef CONFIG_DEBUG_FS
206 struct dentry *debug_dir;
207#endif
208};
209
210struct wb_lock_cookie {
211 bool locked;
212 unsigned long flags;
213};
214
215#ifdef CONFIG_CGROUP_WRITEBACK
216
217/**
218 * wb_tryget - try to increment a wb's refcount
219 * @wb: bdi_writeback to get
220 */
221static inline bool wb_tryget(struct bdi_writeback *wb)
222{
223 if (wb != &wb->bdi->wb)
224 return percpu_ref_tryget(&wb->refcnt);
225 return true;
226}
227
228/**
229 * wb_get - increment a wb's refcount
230 * @wb: bdi_writeback to get
231 */
232static inline void wb_get(struct bdi_writeback *wb)
233{
234 if (wb != &wb->bdi->wb)
235 percpu_ref_get(&wb->refcnt);
236}
237
238/**
239 * wb_put - decrement a wb's refcount
240 * @wb: bdi_writeback to put
241 * @nr: number of references to put
242 */
243static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)
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_many(&wb->refcnt, nr);
255}
256
257/**
258 * wb_put - decrement a wb's refcount
259 * @wb: bdi_writeback to put
260 */
261static inline void wb_put(struct bdi_writeback *wb)
262{
263 wb_put_many(wb, 1);
264}
265
266/**
267 * wb_dying - is a wb dying?
268 * @wb: bdi_writeback of interest
269 *
270 * Returns whether @wb is unlinked and being drained.
271 */
272static inline bool wb_dying(struct bdi_writeback *wb)
273{
274 return percpu_ref_is_dying(&wb->refcnt);
275}
276
277#else /* CONFIG_CGROUP_WRITEBACK */
278
279static inline bool wb_tryget(struct bdi_writeback *wb)
280{
281 return true;
282}
283
284static inline void wb_get(struct bdi_writeback *wb)
285{
286}
287
288static inline void wb_put(struct bdi_writeback *wb)
289{
290}
291
292static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)
293{
294}
295
296static inline bool wb_dying(struct bdi_writeback *wb)
297{
298 return false;
299}
300
301#endif /* CONFIG_CGROUP_WRITEBACK */
302
303#endif /* __LINUX_BACKING_DEV_DEFS_H */
304