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 enum 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  */
49 enum 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 
68 struct 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  *
107  * Each bdi_writeback that is not embedded into the backing_dev_info must hold
108  * a reference to the parent backing_dev_info.  See cgwb_create() for details.
109  */
110 struct bdi_writeback {
111 	struct backing_dev_info *bdi;	/* our parent bdi */
112 
113 	unsigned long state;		/* Always use atomic bitops on this */
114 	unsigned long last_old_flush;	/* last old data flush */
115 
116 	struct list_head b_dirty;	/* dirty inodes */
117 	struct list_head b_io;		/* parked for writeback */
118 	struct list_head b_more_io;	/* parked for more writeback */
119 	struct list_head b_dirty_time;	/* time stamps are dirty */
120 	spinlock_t list_lock;		/* protects the b_* lists */
121 
122 	atomic_t writeback_inodes;	/* number of inodes under writeback */
123 	struct percpu_counter stat[NR_WB_STAT_ITEMS];
124 
125 	unsigned long congested;	/* WB_[a]sync_congested flags */
126 
127 	unsigned long bw_time_stamp;	/* last time write bw is updated */
128 	unsigned long dirtied_stamp;
129 	unsigned long written_stamp;	/* pages written at bw_time_stamp */
130 	unsigned long write_bandwidth;	/* the estimated write bandwidth */
131 	unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */
132 
133 	/*
134 	 * The base dirty throttle rate, re-calculated on every 200ms.
135 	 * All the bdi tasks' dirty rate will be curbed under it.
136 	 * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
137 	 * in small steps and is much more smooth/stable than the latter.
138 	 */
139 	unsigned long dirty_ratelimit;
140 	unsigned long balanced_dirty_ratelimit;
141 
142 	struct fprop_local_percpu completions;
143 	int dirty_exceeded;
144 	enum wb_reason start_all_reason;
145 
146 	spinlock_t work_lock;		/* protects work_list & dwork scheduling */
147 	struct list_head work_list;
148 	struct delayed_work dwork;	/* work item used for writeback */
149 	struct delayed_work bw_dwork;	/* work item used for bandwidth estimate */
150 
151 	unsigned long dirty_sleep;	/* last wait */
152 
153 	struct list_head bdi_node;	/* anchored at bdi->wb_list */
154 
155 #ifdef CONFIG_CGROUP_WRITEBACK
156 	struct percpu_ref refcnt;	/* used only for !root wb's */
157 	struct fprop_local_percpu memcg_completions;
158 	struct cgroup_subsys_state *memcg_css; /* the associated memcg */
159 	struct cgroup_subsys_state *blkcg_css; /* and blkcg */
160 	struct list_head memcg_node;	/* anchored at memcg->cgwb_list */
161 	struct list_head blkcg_node;	/* anchored at blkcg->cgwb_list */
162 	struct list_head b_attached;	/* attached inodes, protected by list_lock */
163 	struct list_head offline_node;	/* anchored at offline_cgwbs */
164 
165 	union {
166 		struct work_struct release_work;
167 		struct rcu_head rcu;
168 	};
169 #endif
170 };
171 
172 struct backing_dev_info {
173 	u64 id;
174 	struct rb_node rb_node; /* keyed by ->id */
175 	struct list_head bdi_list;
176 	unsigned long ra_pages;	/* max readahead in PAGE_SIZE units */
177 	unsigned long io_pages;	/* max allowed IO size */
178 
179 	struct kref refcnt;	/* Reference counter for the structure */
180 	unsigned int capabilities; /* Device capabilities */
181 	unsigned int min_ratio;
182 	unsigned int max_ratio, max_prop_frac;
183 
184 	/*
185 	 * Sum of avg_write_bw of wbs with dirty inodes.  > 0 if there are
186 	 * any dirty wbs, which is depended upon by bdi_has_dirty().
187 	 */
188 	atomic_long_t tot_write_bandwidth;
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 
210 enum {
211 	BLK_RW_ASYNC	= 0,
212 	BLK_RW_SYNC	= 1,
213 };
214 
215 void clear_bdi_congested(struct backing_dev_info *bdi, int sync);
216 void set_bdi_congested(struct backing_dev_info *bdi, int sync);
217 
218 struct wb_lock_cookie {
219 	bool locked;
220 	unsigned long flags;
221 };
222 
223 #ifdef CONFIG_CGROUP_WRITEBACK
224 
225 /**
226  * wb_tryget - try to increment a wb's refcount
227  * @wb: bdi_writeback to get
228  */
wb_tryget(struct bdi_writeback * wb)229 static inline bool wb_tryget(struct bdi_writeback *wb)
230 {
231 	if (wb != &wb->bdi->wb)
232 		return percpu_ref_tryget(&wb->refcnt);
233 	return true;
234 }
235 
236 /**
237  * wb_get - increment a wb's refcount
238  * @wb: bdi_writeback to get
239  */
wb_get(struct bdi_writeback * wb)240 static inline void wb_get(struct bdi_writeback *wb)
241 {
242 	if (wb != &wb->bdi->wb)
243 		percpu_ref_get(&wb->refcnt);
244 }
245 
246 /**
247  * wb_put - decrement a wb's refcount
248  * @wb: bdi_writeback to put
249  * @nr: number of references to put
250  */
wb_put_many(struct bdi_writeback * wb,unsigned long nr)251 static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)
252 {
253 	if (WARN_ON_ONCE(!wb->bdi)) {
254 		/*
255 		 * A driver bug might cause a file to be removed before bdi was
256 		 * initialized.
257 		 */
258 		return;
259 	}
260 
261 	if (wb != &wb->bdi->wb)
262 		percpu_ref_put_many(&wb->refcnt, nr);
263 }
264 
265 /**
266  * wb_put - decrement a wb's refcount
267  * @wb: bdi_writeback to put
268  */
wb_put(struct bdi_writeback * wb)269 static inline void wb_put(struct bdi_writeback *wb)
270 {
271 	wb_put_many(wb, 1);
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  */
wb_dying(struct bdi_writeback * wb)280 static 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 
wb_tryget(struct bdi_writeback * wb)287 static inline bool wb_tryget(struct bdi_writeback *wb)
288 {
289 	return true;
290 }
291 
wb_get(struct bdi_writeback * wb)292 static inline void wb_get(struct bdi_writeback *wb)
293 {
294 }
295 
wb_put(struct bdi_writeback * wb)296 static inline void wb_put(struct bdi_writeback *wb)
297 {
298 }
299 
wb_put_many(struct bdi_writeback * wb,unsigned long nr)300 static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)
301 {
302 }
303 
wb_dying(struct bdi_writeback * wb)304 static inline bool wb_dying(struct bdi_writeback *wb)
305 {
306 	return false;
307 }
308 
309 #endif	/* CONFIG_CGROUP_WRITEBACK */
310 
311 #endif	/* __LINUX_BACKING_DEV_DEFS_H */
312