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TOMOYO Linux Cross Reference
Linux/include/linux/backing-dev-defs.h

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  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 
 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  */
 77 struct 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  */
109 struct 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 
167 struct 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 
210 enum {
211         BLK_RW_ASYNC    = 0,
212         BLK_RW_SYNC     = 1,
213 };
214 
215 void clear_wb_congested(struct bdi_writeback_congested *congested, int sync);
216 void set_wb_congested(struct bdi_writeback_congested *congested, int sync);
217 
218 static inline void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
219 {
220         clear_wb_congested(bdi->wb.congested, sync);
221 }
222 
223 static inline void set_bdi_congested(struct backing_dev_info *bdi, int sync)
224 {
225         set_wb_congested(bdi->wb.congested, sync);
226 }
227 
228 struct 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  */
239 static 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  */
250 static 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  */
260 static 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  */
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 
287 static inline bool wb_tryget(struct bdi_writeback *wb)
288 {
289         return true;
290 }
291 
292 static inline void wb_get(struct bdi_writeback *wb)
293 {
294 }
295 
296 static inline void wb_put(struct bdi_writeback *wb)
297 {
298 }
299 
300 static 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 

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