1 /*
2 * include/linux/writeback.h
3 */
4 #ifndef WRITEBACK_H
5 #define WRITEBACK_H
6
7 #include <linux/sched.h>
8 #include <linux/workqueue.h>
9 #include <linux/fs.h>
10 #include <linux/flex_proportions.h>
11 #include <linux/backing-dev-defs.h>
12
13 DECLARE_PER_CPU(int, dirty_throttle_leaks);
14
15 /*
16 * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
17 *
18 * (thresh - thresh/DIRTY_FULL_SCOPE, thresh)
19 *
20 * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
21 * time) for the dirty pages to drop, unless written enough pages.
22 *
23 * The global dirty threshold is normally equal to the global dirty limit,
24 * except when the system suddenly allocates a lot of anonymous memory and
25 * knocks down the global dirty threshold quickly, in which case the global
26 * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
27 */
28 #define DIRTY_SCOPE 8
29 #define DIRTY_FULL_SCOPE (DIRTY_SCOPE / 2)
30
31 struct backing_dev_info;
32
33 /*
34 * fs/fs-writeback.c
35 */
36 enum writeback_sync_modes {
37 WB_SYNC_NONE, /* Don't wait on anything */
38 WB_SYNC_ALL, /* Wait on every mapping */
39 };
40
41 /*
42 * why some writeback work was initiated
43 */
44 enum wb_reason {
45 WB_REASON_BACKGROUND,
46 WB_REASON_TRY_TO_FREE_PAGES,
47 WB_REASON_SYNC,
48 WB_REASON_PERIODIC,
49 WB_REASON_LAPTOP_TIMER,
50 WB_REASON_FREE_MORE_MEM,
51 WB_REASON_FS_FREE_SPACE,
52 /*
53 * There is no bdi forker thread any more and works are done
54 * by emergency worker, however, this is TPs userland visible
55 * and we'll be exposing exactly the same information,
56 * so it has a mismatch name.
57 */
58 WB_REASON_FORKER_THREAD,
59
60 WB_REASON_MAX,
61 };
62
63 /*
64 * A control structure which tells the writeback code what to do. These are
65 * always on the stack, and hence need no locking. They are always initialised
66 * in a manner such that unspecified fields are set to zero.
67 */
68 struct writeback_control {
69 long nr_to_write; /* Write this many pages, and decrement
70 this for each page written */
71 long pages_skipped; /* Pages which were not written */
72
73 /*
74 * For a_ops->writepages(): if start or end are non-zero then this is
75 * a hint that the filesystem need only write out the pages inside that
76 * byterange. The byte at `end' is included in the writeout request.
77 */
78 loff_t range_start;
79 loff_t range_end;
80
81 enum writeback_sync_modes sync_mode;
82
83 unsigned for_kupdate:1; /* A kupdate writeback */
84 unsigned for_background:1; /* A background writeback */
85 unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */
86 unsigned for_reclaim:1; /* Invoked from the page allocator */
87 unsigned range_cyclic:1; /* range_start is cyclic */
88 unsigned for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
89 #ifdef CONFIG_CGROUP_WRITEBACK
90 struct bdi_writeback *wb; /* wb this writeback is issued under */
91 struct inode *inode; /* inode being written out */
92
93 /* foreign inode detection, see wbc_detach_inode() */
94 int wb_id; /* current wb id */
95 int wb_lcand_id; /* last foreign candidate wb id */
96 int wb_tcand_id; /* this foreign candidate wb id */
97 size_t wb_bytes; /* bytes written by current wb */
98 size_t wb_lcand_bytes; /* bytes written by last candidate */
99 size_t wb_tcand_bytes; /* bytes written by this candidate */
100 #endif
101 };
102
103 /*
104 * A wb_domain represents a domain that wb's (bdi_writeback's) belong to
105 * and are measured against each other in. There always is one global
106 * domain, global_wb_domain, that every wb in the system is a member of.
107 * This allows measuring the relative bandwidth of each wb to distribute
108 * dirtyable memory accordingly.
109 */
110 struct wb_domain {
111 spinlock_t lock;
112
113 /*
114 * Scale the writeback cache size proportional to the relative
115 * writeout speed.
116 *
117 * We do this by keeping a floating proportion between BDIs, based
118 * on page writeback completions [end_page_writeback()]. Those
119 * devices that write out pages fastest will get the larger share,
120 * while the slower will get a smaller share.
121 *
122 * We use page writeout completions because we are interested in
123 * getting rid of dirty pages. Having them written out is the
124 * primary goal.
125 *
126 * We introduce a concept of time, a period over which we measure
127 * these events, because demand can/will vary over time. The length
128 * of this period itself is measured in page writeback completions.
129 */
130 struct fprop_global completions;
131 struct timer_list period_timer; /* timer for aging of completions */
132 unsigned long period_time;
133
134 /*
135 * The dirtyable memory and dirty threshold could be suddenly
136 * knocked down by a large amount (eg. on the startup of KVM in a
137 * swapless system). This may throw the system into deep dirty
138 * exceeded state and throttle heavy/light dirtiers alike. To
139 * retain good responsiveness, maintain global_dirty_limit for
140 * tracking slowly down to the knocked down dirty threshold.
141 *
142 * Both fields are protected by ->lock.
143 */
144 unsigned long dirty_limit_tstamp;
145 unsigned long dirty_limit;
146 };
147
148 /**
149 * wb_domain_size_changed - memory available to a wb_domain has changed
150 * @dom: wb_domain of interest
151 *
152 * This function should be called when the amount of memory available to
153 * @dom has changed. It resets @dom's dirty limit parameters to prevent
154 * the past values which don't match the current configuration from skewing
155 * dirty throttling. Without this, when memory size of a wb_domain is
156 * greatly reduced, the dirty throttling logic may allow too many pages to
157 * be dirtied leading to consecutive unnecessary OOMs and may get stuck in
158 * that situation.
159 */
wb_domain_size_changed(struct wb_domain * dom)160 static inline void wb_domain_size_changed(struct wb_domain *dom)
161 {
162 spin_lock(&dom->lock);
163 dom->dirty_limit_tstamp = jiffies;
164 dom->dirty_limit = 0;
165 spin_unlock(&dom->lock);
166 }
167
168 /*
169 * fs/fs-writeback.c
170 */
171 struct bdi_writeback;
172 void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
173 void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
174 enum wb_reason reason);
175 bool try_to_writeback_inodes_sb(struct super_block *, enum wb_reason reason);
176 bool try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
177 enum wb_reason reason);
178 void sync_inodes_sb(struct super_block *);
179 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
180 void inode_wait_for_writeback(struct inode *inode);
181
182 /* writeback.h requires fs.h; it, too, is not included from here. */
wait_on_inode(struct inode * inode)183 static inline void wait_on_inode(struct inode *inode)
184 {
185 might_sleep();
186 wait_on_bit(&inode->i_state, __I_NEW, TASK_UNINTERRUPTIBLE);
187 }
188
189 #ifdef CONFIG_CGROUP_WRITEBACK
190
191 #include <linux/cgroup.h>
192 #include <linux/bio.h>
193
194 void __inode_attach_wb(struct inode *inode, struct page *page);
195 void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
196 struct inode *inode)
197 __releases(&inode->i_lock);
198 void wbc_detach_inode(struct writeback_control *wbc);
199 void wbc_account_io(struct writeback_control *wbc, struct page *page,
200 size_t bytes);
201
202 /**
203 * inode_attach_wb - associate an inode with its wb
204 * @inode: inode of interest
205 * @page: page being dirtied (may be NULL)
206 *
207 * If @inode doesn't have its wb, associate it with the wb matching the
208 * memcg of @page or, if @page is NULL, %current. May be called w/ or w/o
209 * @inode->i_lock.
210 */
inode_attach_wb(struct inode * inode,struct page * page)211 static inline void inode_attach_wb(struct inode *inode, struct page *page)
212 {
213 if (!inode->i_wb)
214 __inode_attach_wb(inode, page);
215 }
216
217 /**
218 * inode_detach_wb - disassociate an inode from its wb
219 * @inode: inode of interest
220 *
221 * @inode is being freed. Detach from its wb.
222 */
inode_detach_wb(struct inode * inode)223 static inline void inode_detach_wb(struct inode *inode)
224 {
225 if (inode->i_wb) {
226 wb_put(inode->i_wb);
227 inode->i_wb = NULL;
228 }
229 }
230
231 /**
232 * wbc_attach_fdatawrite_inode - associate wbc and inode for fdatawrite
233 * @wbc: writeback_control of interest
234 * @inode: target inode
235 *
236 * This function is to be used by __filemap_fdatawrite_range(), which is an
237 * alternative entry point into writeback code, and first ensures @inode is
238 * associated with a bdi_writeback and attaches it to @wbc.
239 */
wbc_attach_fdatawrite_inode(struct writeback_control * wbc,struct inode * inode)240 static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
241 struct inode *inode)
242 {
243 spin_lock(&inode->i_lock);
244 inode_attach_wb(inode, NULL);
245 wbc_attach_and_unlock_inode(wbc, inode);
246 }
247
248 /**
249 * wbc_init_bio - writeback specific initializtion of bio
250 * @wbc: writeback_control for the writeback in progress
251 * @bio: bio to be initialized
252 *
253 * @bio is a part of the writeback in progress controlled by @wbc. Perform
254 * writeback specific initialization. This is used to apply the cgroup
255 * writeback context.
256 */
wbc_init_bio(struct writeback_control * wbc,struct bio * bio)257 static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
258 {
259 /*
260 * pageout() path doesn't attach @wbc to the inode being written
261 * out. This is intentional as we don't want the function to block
262 * behind a slow cgroup. Ultimately, we want pageout() to kick off
263 * regular writeback instead of writing things out itself.
264 */
265 if (wbc->wb)
266 bio_associate_blkcg(bio, wbc->wb->blkcg_css);
267 }
268
269 #else /* CONFIG_CGROUP_WRITEBACK */
270
inode_attach_wb(struct inode * inode,struct page * page)271 static inline void inode_attach_wb(struct inode *inode, struct page *page)
272 {
273 }
274
inode_detach_wb(struct inode * inode)275 static inline void inode_detach_wb(struct inode *inode)
276 {
277 }
278
wbc_attach_and_unlock_inode(struct writeback_control * wbc,struct inode * inode)279 static inline void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
280 struct inode *inode)
281 __releases(&inode->i_lock)
282 {
283 spin_unlock(&inode->i_lock);
284 }
285
wbc_attach_fdatawrite_inode(struct writeback_control * wbc,struct inode * inode)286 static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
287 struct inode *inode)
288 {
289 }
290
wbc_detach_inode(struct writeback_control * wbc)291 static inline void wbc_detach_inode(struct writeback_control *wbc)
292 {
293 }
294
wbc_init_bio(struct writeback_control * wbc,struct bio * bio)295 static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
296 {
297 }
298
wbc_account_io(struct writeback_control * wbc,struct page * page,size_t bytes)299 static inline void wbc_account_io(struct writeback_control *wbc,
300 struct page *page, size_t bytes)
301 {
302 }
303
304 #endif /* CONFIG_CGROUP_WRITEBACK */
305
306 /*
307 * mm/page-writeback.c
308 */
309 #ifdef CONFIG_BLOCK
310 void laptop_io_completion(struct backing_dev_info *info);
311 void laptop_sync_completion(void);
312 void laptop_mode_sync(struct work_struct *work);
313 void laptop_mode_timer_fn(unsigned long data);
314 #else
laptop_sync_completion(void)315 static inline void laptop_sync_completion(void) { }
316 #endif
317 void throttle_vm_writeout(gfp_t gfp_mask);
318 bool zone_dirty_ok(struct zone *zone);
319 int wb_domain_init(struct wb_domain *dom, gfp_t gfp);
320 #ifdef CONFIG_CGROUP_WRITEBACK
321 void wb_domain_exit(struct wb_domain *dom);
322 #endif
323
324 extern struct wb_domain global_wb_domain;
325
326 /* These are exported to sysctl. */
327 extern int dirty_background_ratio;
328 extern unsigned long dirty_background_bytes;
329 extern int vm_dirty_ratio;
330 extern unsigned long vm_dirty_bytes;
331 extern unsigned int dirty_writeback_interval;
332 extern unsigned int dirty_expire_interval;
333 extern unsigned int dirtytime_expire_interval;
334 extern int vm_highmem_is_dirtyable;
335 extern int block_dump;
336 extern int laptop_mode;
337
338 extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
339 void __user *buffer, size_t *lenp,
340 loff_t *ppos);
341 extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
342 void __user *buffer, size_t *lenp,
343 loff_t *ppos);
344 extern int dirty_ratio_handler(struct ctl_table *table, int write,
345 void __user *buffer, size_t *lenp,
346 loff_t *ppos);
347 extern int dirty_bytes_handler(struct ctl_table *table, int write,
348 void __user *buffer, size_t *lenp,
349 loff_t *ppos);
350 int dirtytime_interval_handler(struct ctl_table *table, int write,
351 void __user *buffer, size_t *lenp, loff_t *ppos);
352
353 struct ctl_table;
354 int dirty_writeback_centisecs_handler(struct ctl_table *, int,
355 void __user *, size_t *, loff_t *);
356
357 void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
358 unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
359
360 void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time);
361 void page_writeback_init(void);
362 void balance_dirty_pages_ratelimited(struct address_space *mapping);
363 bool wb_over_bg_thresh(struct bdi_writeback *wb);
364
365 typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
366 void *data);
367
368 int generic_writepages(struct address_space *mapping,
369 struct writeback_control *wbc);
370 void tag_pages_for_writeback(struct address_space *mapping,
371 pgoff_t start, pgoff_t end);
372 int write_cache_pages(struct address_space *mapping,
373 struct writeback_control *wbc, writepage_t writepage,
374 void *data);
375 int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
376 void writeback_set_ratelimit(void);
377 void tag_pages_for_writeback(struct address_space *mapping,
378 pgoff_t start, pgoff_t end);
379
380 void account_page_redirty(struct page *page);
381
382 #endif /* WRITEBACK_H */
383