xref: /linux/include/linux/backing-dev-defs.h (revision 79790b6818e96c58fe2bffee1b418c16e64e7b80)
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_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  */
44 enum 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 
63 struct 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  */
105 struct 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 
163 struct 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 
206 struct 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  */
wb_tryget(struct bdi_writeback * wb)217 static 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  */
wb_get(struct bdi_writeback * wb)228 static 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  */
wb_put_many(struct bdi_writeback * wb,unsigned long nr)239 static 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  */
wb_put(struct bdi_writeback * wb)257 static 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  */
wb_dying(struct bdi_writeback * wb)268 static 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 
wb_tryget(struct bdi_writeback * wb)275 static inline bool wb_tryget(struct bdi_writeback *wb)
276 {
277 	return true;
278 }
279 
wb_get(struct bdi_writeback * wb)280 static inline void wb_get(struct bdi_writeback *wb)
281 {
282 }
283 
wb_put(struct bdi_writeback * wb)284 static inline void wb_put(struct bdi_writeback *wb)
285 {
286 }
287 
wb_put_many(struct bdi_writeback * wb,unsigned long nr)288 static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)
289 {
290 }
291 
wb_dying(struct bdi_writeback * wb)292 static 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