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
17 struct page;
18 struct device;
19 struct dentry;
20
21 /*
22 * Bits in bdi_writeback.state
23 */
24 enum 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
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
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
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,
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 WB_REASON_FOREIGN_FLUSH,
67
68 WB_REASON_MAX,
69 };
70
71 struct wb_completion {
72 atomic_t cnt;
73 wait_queue_head_t *waitq;
74 };
75
76 #define __WB_COMPLETION_INIT(_waitq) \
77 (struct wb_completion){ .cnt = ATOMIC_INIT(1), .waitq = (_waitq) }
78
79 /*
80 * If one wants to wait for one or more wb_writeback_works, each work's
81 * ->done should be set to a wb_completion defined using the following
82 * macro. Once all work items are issued with wb_queue_work(), the caller
83 * can wait for the completion of all using wb_wait_for_completion(). Work
84 * items which are waited upon aren't freed automatically on completion.
85 */
86 #define WB_COMPLETION_INIT(bdi) __WB_COMPLETION_INIT(&(bdi)->wb_waitq)
87
88 #define DEFINE_WB_COMPLETION(cmpl, bdi) \
89 struct wb_completion cmpl = WB_COMPLETION_INIT(bdi)
90
91 /*
92 * For cgroup writeback, multiple wb's may map to the same blkcg. Those
93 * wb's can operate mostly independently but should share the congested
94 * state. To facilitate such sharing, the congested state is tracked using
95 * the following struct which is created on demand, indexed by blkcg ID on
96 * its bdi, and refcounted.
97 */
98 struct bdi_writeback_congested {
99 unsigned long state; /* WB_[a]sync_congested flags */
100 refcount_t refcnt; /* nr of attached wb's and blkg */
101
102 #ifdef CONFIG_CGROUP_WRITEBACK
103 struct backing_dev_info *__bdi; /* the associated bdi, set to NULL
104 * on bdi unregistration. For memcg-wb
105 * internal use only! */
106 int blkcg_id; /* ID of the associated blkcg */
107 struct rb_node rb_node; /* on bdi->cgwb_congestion_tree */
108 #endif
109 };
110
111 /*
112 * Each wb (bdi_writeback) can perform writeback operations, is measured
113 * and throttled, independently. Without cgroup writeback, each bdi
114 * (bdi_writeback) is served by its embedded bdi->wb.
115 *
116 * On the default hierarchy, blkcg implicitly enables memcg. This allows
117 * using memcg's page ownership for attributing writeback IOs, and every
118 * memcg - blkcg combination can be served by its own wb by assigning a
119 * dedicated wb to each memcg, which enables isolation across different
120 * cgroups and propagation of IO back pressure down from the IO layer upto
121 * the tasks which are generating the dirty pages to be written back.
122 *
123 * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
124 * refcounted with the number of inodes attached to it, and pins the memcg
125 * and the corresponding blkcg. As the corresponding blkcg for a memcg may
126 * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
127 * is tested for blkcg after lookup and removed from index on mismatch so
128 * that a new wb for the combination can be created.
129 */
130 struct bdi_writeback {
131 struct backing_dev_info *bdi; /* our parent bdi */
132
133 unsigned long state; /* Always use atomic bitops on this */
134 unsigned long last_old_flush; /* last old data flush */
135
136 struct list_head b_dirty; /* dirty inodes */
137 struct list_head b_io; /* parked for writeback */
138 struct list_head b_more_io; /* parked for more writeback */
139 struct list_head b_dirty_time; /* time stamps are dirty */
140 spinlock_t list_lock; /* protects the b_* lists */
141
142 struct percpu_counter stat[NR_WB_STAT_ITEMS];
143
144 struct bdi_writeback_congested *congested;
145
146 unsigned long bw_time_stamp; /* last time write bw is updated */
147 unsigned long dirtied_stamp;
148 unsigned long written_stamp; /* pages written at bw_time_stamp */
149 unsigned long write_bandwidth; /* the estimated write bandwidth */
150 unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */
151
152 /*
153 * The base dirty throttle rate, re-calculated on every 200ms.
154 * All the bdi tasks' dirty rate will be curbed under it.
155 * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
156 * in small steps and is much more smooth/stable than the latter.
157 */
158 unsigned long dirty_ratelimit;
159 unsigned long balanced_dirty_ratelimit;
160
161 struct fprop_local_percpu completions;
162 int dirty_exceeded;
163 enum wb_reason start_all_reason;
164
165 spinlock_t work_lock; /* protects work_list & dwork scheduling */
166 struct list_head work_list;
167 struct delayed_work dwork; /* work item used for writeback */
168
169 unsigned long dirty_sleep; /* last wait */
170
171 struct list_head bdi_node; /* anchored at bdi->wb_list */
172
173 #ifdef CONFIG_CGROUP_WRITEBACK
174 struct percpu_ref refcnt; /* used only for !root wb's */
175 struct fprop_local_percpu memcg_completions;
176 struct cgroup_subsys_state *memcg_css; /* the associated memcg */
177 struct cgroup_subsys_state *blkcg_css; /* and blkcg */
178 struct list_head memcg_node; /* anchored at memcg->cgwb_list */
179 struct list_head blkcg_node; /* anchored at blkcg->cgwb_list */
180
181 union {
182 struct work_struct release_work;
183 struct rcu_head rcu;
184 };
185 #endif
186 };
187
188 struct backing_dev_info {
189 u64 id;
190 struct rb_node rb_node; /* keyed by ->id */
191 struct list_head bdi_list;
192 unsigned long ra_pages; /* max readahead in PAGE_SIZE units */
193 unsigned long io_pages; /* max allowed IO size */
194 congested_fn *congested_fn; /* Function pointer if device is md/dm */
195 void *congested_data; /* Pointer to aux data for congested func */
196
197 const char *name;
198
199 struct kref refcnt; /* Reference counter for the structure */
200 unsigned int capabilities; /* Device capabilities */
201 unsigned int min_ratio;
202 unsigned int max_ratio, max_prop_frac;
203
204 /*
205 * Sum of avg_write_bw of wbs with dirty inodes. > 0 if there are
206 * any dirty wbs, which is depended upon by bdi_has_dirty().
207 */
208 atomic_long_t tot_write_bandwidth;
209
210 struct bdi_writeback wb; /* the root writeback info for this bdi */
211 struct list_head wb_list; /* list of all wbs */
212 #ifdef CONFIG_CGROUP_WRITEBACK
213 struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
214 struct rb_root cgwb_congested_tree; /* their congested states */
215 struct mutex cgwb_release_mutex; /* protect shutdown of wb structs */
216 struct rw_semaphore wb_switch_rwsem; /* no cgwb switch while syncing */
217 #else
218 struct bdi_writeback_congested *wb_congested;
219 #endif
220 wait_queue_head_t wb_waitq;
221
222 struct device *dev;
223 char dev_name[64];
224 struct device *owner;
225
226 struct timer_list laptop_mode_wb_timer;
227
228 #ifdef CONFIG_DEBUG_FS
229 struct dentry *debug_dir;
230 #endif
231 };
232
233 enum {
234 BLK_RW_ASYNC = 0,
235 BLK_RW_SYNC = 1,
236 };
237
238 void clear_wb_congested(struct bdi_writeback_congested *congested, int sync);
239 void set_wb_congested(struct bdi_writeback_congested *congested, int sync);
240
241 static inline void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
242 {
243 clear_wb_congested(bdi->wb.congested, sync);
244 }
245
246 static inline void set_bdi_congested(struct backing_dev_info *bdi, int sync)
247 {
248 set_wb_congested(bdi->wb.congested, sync);
249 }
250
251 struct wb_lock_cookie {
252 bool locked;
253 unsigned long flags;
254 };
255
256 #ifdef CONFIG_CGROUP_WRITEBACK
257
258 /**
259 * wb_tryget - try to increment a wb's refcount
260 * @wb: bdi_writeback to get
261 */
262 static inline bool wb_tryget(struct bdi_writeback *wb)
263 {
264 if (wb != &wb->bdi->wb)
265 return percpu_ref_tryget(&wb->refcnt);
266 return true;
267 }
268
269 /**
270 * wb_get - increment a wb's refcount
271 * @wb: bdi_writeback to get
272 */
273 static inline void wb_get(struct bdi_writeback *wb)
274 {
275 if (wb != &wb->bdi->wb)
276 percpu_ref_get(&wb->refcnt);
277 }
278
279 /**
280 * wb_put - decrement a wb's refcount
281 * @wb: bdi_writeback to put
282 */
283 static inline void wb_put(struct bdi_writeback *wb)
284 {
285 if (WARN_ON_ONCE(!wb->bdi)) {
286 /*
287 * A driver bug might cause a file to be removed before bdi was
288 * initialized.
289 */
290 return;
291 }
292
293 if (wb != &wb->bdi->wb)
294 percpu_ref_put(&wb->refcnt);
295 }
296
297 /**
298 * wb_dying - is a wb dying?
299 * @wb: bdi_writeback of interest
300 *
301 * Returns whether @wb is unlinked and being drained.
302 */
303 static inline bool wb_dying(struct bdi_writeback *wb)
304 {
305 return percpu_ref_is_dying(&wb->refcnt);
306 }
307
308 #else /* CONFIG_CGROUP_WRITEBACK */
309
310 static inline bool wb_tryget(struct bdi_writeback *wb)
311 {
312 return true;
313 }
314
315 static inline void wb_get(struct bdi_writeback *wb)
316 {
317 }
318
319 static inline void wb_put(struct bdi_writeback *wb)
320 {
321 }
322
323 static inline bool wb_dying(struct bdi_writeback *wb)
324 {
325 return false;
326 }
327
328 #endif /* CONFIG_CGROUP_WRITEBACK */
329
330 #endif /* __LINUX_BACKING_DEV_DEFS_H */