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1 : : /* SPDX-License-Identifier: GPL-2.0 */
2 : : /*
3 : : * include/linux/writeback.h
4 : : */
5 : : #ifndef WRITEBACK_H
6 : : #define WRITEBACK_H
7 : :
8 : : #include <linux/sched.h>
9 : : #include <linux/workqueue.h>
10 : : #include <linux/fs.h>
11 : : #include <linux/flex_proportions.h>
12 : : #include <linux/backing-dev-defs.h>
13 : : #include <linux/blk_types.h>
14 : : #include <linux/blk-cgroup.h>
15 : :
16 : : struct bio;
17 : :
18 : : DECLARE_PER_CPU(int, dirty_throttle_leaks);
19 : :
20 : : /*
21 : : * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
22 : : *
23 : : * (thresh - thresh/DIRTY_FULL_SCOPE, thresh)
24 : : *
25 : : * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
26 : : * time) for the dirty pages to drop, unless written enough pages.
27 : : *
28 : : * The global dirty threshold is normally equal to the global dirty limit,
29 : : * except when the system suddenly allocates a lot of anonymous memory and
30 : : * knocks down the global dirty threshold quickly, in which case the global
31 : : * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
32 : : */
33 : : #define DIRTY_SCOPE 8
34 : : #define DIRTY_FULL_SCOPE (DIRTY_SCOPE / 2)
35 : :
36 : : struct backing_dev_info;
37 : :
38 : : /*
39 : : * fs/fs-writeback.c
40 : : */
41 : : enum writeback_sync_modes {
42 : : WB_SYNC_NONE, /* Don't wait on anything */
43 : : WB_SYNC_ALL, /* Wait on every mapping */
44 : : };
45 : :
46 : : /*
47 : : * A control structure which tells the writeback code what to do. These are
48 : : * always on the stack, and hence need no locking. They are always initialised
49 : : * in a manner such that unspecified fields are set to zero.
50 : : */
51 : : struct writeback_control {
52 : : long nr_to_write; /* Write this many pages, and decrement
53 : : this for each page written */
54 : : long pages_skipped; /* Pages which were not written */
55 : :
56 : : /*
57 : : * For a_ops->writepages(): if start or end are non-zero then this is
58 : : * a hint that the filesystem need only write out the pages inside that
59 : : * byterange. The byte at `end' is included in the writeout request.
60 : : */
61 : : loff_t range_start;
62 : : loff_t range_end;
63 : :
64 : : enum writeback_sync_modes sync_mode;
65 : :
66 : : unsigned for_kupdate:1; /* A kupdate writeback */
67 : : unsigned for_background:1; /* A background writeback */
68 : : unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */
69 : : unsigned for_reclaim:1; /* Invoked from the page allocator */
70 : : unsigned range_cyclic:1; /* range_start is cyclic */
71 : : unsigned for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
72 : :
73 : : /*
74 : : * When writeback IOs are bounced through async layers, only the
75 : : * initial synchronous phase should be accounted towards inode
76 : : * cgroup ownership arbitration to avoid confusion. Later stages
77 : : * can set the following flag to disable the accounting.
78 : : */
79 : : unsigned no_cgroup_owner:1;
80 : :
81 : : unsigned punt_to_cgroup:1; /* cgrp punting, see __REQ_CGROUP_PUNT */
82 : :
83 : : #ifdef CONFIG_CGROUP_WRITEBACK
84 : : struct bdi_writeback *wb; /* wb this writeback is issued under */
85 : : struct inode *inode; /* inode being written out */
86 : :
87 : : /* foreign inode detection, see wbc_detach_inode() */
88 : : int wb_id; /* current wb id */
89 : : int wb_lcand_id; /* last foreign candidate wb id */
90 : : int wb_tcand_id; /* this foreign candidate wb id */
91 : : size_t wb_bytes; /* bytes written by current wb */
92 : : size_t wb_lcand_bytes; /* bytes written by last candidate */
93 : : size_t wb_tcand_bytes; /* bytes written by this candidate */
94 : : #endif
95 : : };
96 : :
97 : : static inline int wbc_to_write_flags(struct writeback_control *wbc)
98 : : {
99 : : int flags = 0;
100 : :
101 [ - + ]: 73049 : if (wbc->punt_to_cgroup)
102 : : flags = REQ_CGROUP_PUNT;
103 : :
104 [ + + ]: 73049 : if (wbc->sync_mode == WB_SYNC_ALL)
105 : 14476 : flags |= REQ_SYNC;
106 [ + + ]: 58573 : else if (wbc->for_kupdate || wbc->for_background)
107 : 52994 : flags |= REQ_BACKGROUND;
108 : :
109 : : return flags;
110 : : }
111 : :
112 : : static inline struct cgroup_subsys_state *
113 : : wbc_blkcg_css(struct writeback_control *wbc)
114 : : {
115 : : #ifdef CONFIG_CGROUP_WRITEBACK
116 : : if (wbc->wb)
117 : : return wbc->wb->blkcg_css;
118 : : #endif
119 : : return blkcg_root_css;
120 : : }
121 : :
122 : : /*
123 : : * A wb_domain represents a domain that wb's (bdi_writeback's) belong to
124 : : * and are measured against each other in. There always is one global
125 : : * domain, global_wb_domain, that every wb in the system is a member of.
126 : : * This allows measuring the relative bandwidth of each wb to distribute
127 : : * dirtyable memory accordingly.
128 : : */
129 : : struct wb_domain {
130 : : spinlock_t lock;
131 : :
132 : : /*
133 : : * Scale the writeback cache size proportional to the relative
134 : : * writeout speed.
135 : : *
136 : : * We do this by keeping a floating proportion between BDIs, based
137 : : * on page writeback completions [end_page_writeback()]. Those
138 : : * devices that write out pages fastest will get the larger share,
139 : : * while the slower will get a smaller share.
140 : : *
141 : : * We use page writeout completions because we are interested in
142 : : * getting rid of dirty pages. Having them written out is the
143 : : * primary goal.
144 : : *
145 : : * We introduce a concept of time, a period over which we measure
146 : : * these events, because demand can/will vary over time. The length
147 : : * of this period itself is measured in page writeback completions.
148 : : */
149 : : struct fprop_global completions;
150 : : struct timer_list period_timer; /* timer for aging of completions */
151 : : unsigned long period_time;
152 : :
153 : : /*
154 : : * The dirtyable memory and dirty threshold could be suddenly
155 : : * knocked down by a large amount (eg. on the startup of KVM in a
156 : : * swapless system). This may throw the system into deep dirty
157 : : * exceeded state and throttle heavy/light dirtiers alike. To
158 : : * retain good responsiveness, maintain global_dirty_limit for
159 : : * tracking slowly down to the knocked down dirty threshold.
160 : : *
161 : : * Both fields are protected by ->lock.
162 : : */
163 : : unsigned long dirty_limit_tstamp;
164 : : unsigned long dirty_limit;
165 : : };
166 : :
167 : : /**
168 : : * wb_domain_size_changed - memory available to a wb_domain has changed
169 : : * @dom: wb_domain of interest
170 : : *
171 : : * This function should be called when the amount of memory available to
172 : : * @dom has changed. It resets @dom's dirty limit parameters to prevent
173 : : * the past values which don't match the current configuration from skewing
174 : : * dirty throttling. Without this, when memory size of a wb_domain is
175 : : * greatly reduced, the dirty throttling logic may allow too many pages to
176 : : * be dirtied leading to consecutive unnecessary OOMs and may get stuck in
177 : : * that situation.
178 : : */
179 : 2070 : static inline void wb_domain_size_changed(struct wb_domain *dom)
180 : : {
181 : : spin_lock(&dom->lock);
182 : 2070 : dom->dirty_limit_tstamp = jiffies;
183 : 2070 : dom->dirty_limit = 0;
184 : : spin_unlock(&dom->lock);
185 : 2070 : }
186 : :
187 : : /*
188 : : * fs/fs-writeback.c
189 : : */
190 : : struct bdi_writeback;
191 : : void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
192 : : void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
193 : : enum wb_reason reason);
194 : : void try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason);
195 : : void sync_inodes_sb(struct super_block *);
196 : : void wakeup_flusher_threads(enum wb_reason reason);
197 : : void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
198 : : enum wb_reason reason);
199 : : void inode_wait_for_writeback(struct inode *inode);
200 : :
201 : : /* writeback.h requires fs.h; it, too, is not included from here. */
202 : : static inline void wait_on_inode(struct inode *inode)
203 : : {
204 : 115084 : might_sleep();
205 : 115084 : wait_on_bit(&inode->i_state, __I_NEW, TASK_UNINTERRUPTIBLE);
206 : : }
207 : :
208 : : #ifdef CONFIG_CGROUP_WRITEBACK
209 : :
210 : : #include <linux/cgroup.h>
211 : : #include <linux/bio.h>
212 : :
213 : : void __inode_attach_wb(struct inode *inode, struct page *page);
214 : : void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
215 : : struct inode *inode)
216 : : __releases(&inode->i_lock);
217 : : void wbc_detach_inode(struct writeback_control *wbc);
218 : : void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
219 : : size_t bytes);
220 : : int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr_pages,
221 : : enum wb_reason reason, struct wb_completion *done);
222 : : void cgroup_writeback_umount(void);
223 : :
224 : : /**
225 : : * inode_attach_wb - associate an inode with its wb
226 : : * @inode: inode of interest
227 : : * @page: page being dirtied (may be NULL)
228 : : *
229 : : * If @inode doesn't have its wb, associate it with the wb matching the
230 : : * memcg of @page or, if @page is NULL, %current. May be called w/ or w/o
231 : : * @inode->i_lock.
232 : : */
233 : : static inline void inode_attach_wb(struct inode *inode, struct page *page)
234 : : {
235 [ + + ]: 709993 : if (!inode->i_wb)
236 : 367812 : __inode_attach_wb(inode, page);
237 : : }
238 : :
239 : : /**
240 : : * inode_detach_wb - disassociate an inode from its wb
241 : : * @inode: inode of interest
242 : : *
243 : : * @inode is being freed. Detach from its wb.
244 : : */
245 : 1730831 : static inline void inode_detach_wb(struct inode *inode)
246 : : {
247 [ + + ]: 1730831 : if (inode->i_wb) {
248 [ - + # # ]: 43541 : WARN_ON_ONCE(!(inode->i_state & I_CLEAR));
249 : 43541 : wb_put(inode->i_wb);
250 : 43542 : inode->i_wb = NULL;
251 : : }
252 : 1730832 : }
253 : :
254 : : /**
255 : : * wbc_attach_fdatawrite_inode - associate wbc and inode for fdatawrite
256 : : * @wbc: writeback_control of interest
257 : : * @inode: target inode
258 : : *
259 : : * This function is to be used by __filemap_fdatawrite_range(), which is an
260 : : * alternative entry point into writeback code, and first ensures @inode is
261 : : * associated with a bdi_writeback and attaches it to @wbc.
262 : : */
263 : 1585 : static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
264 : : struct inode *inode)
265 : : {
266 : : spin_lock(&inode->i_lock);
267 : : inode_attach_wb(inode, NULL);
268 : 1585 : wbc_attach_and_unlock_inode(wbc, inode);
269 : 1585 : }
270 : :
271 : : /**
272 : : * wbc_init_bio - writeback specific initializtion of bio
273 : : * @wbc: writeback_control for the writeback in progress
274 : : * @bio: bio to be initialized
275 : : *
276 : : * @bio is a part of the writeback in progress controlled by @wbc. Perform
277 : : * writeback specific initialization. This is used to apply the cgroup
278 : : * writeback context. Must be called after the bio has been associated with
279 : : * a device.
280 : : */
281 : : static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
282 : : {
283 : : /*
284 : : * pageout() path doesn't attach @wbc to the inode being written
285 : : * out. This is intentional as we don't want the function to block
286 : : * behind a slow cgroup. Ultimately, we want pageout() to kick off
287 : : * regular writeback instead of writing things out itself.
288 : : */
289 [ - + ]: 84003 : if (wbc->wb)
290 : 0 : bio_associate_blkg_from_css(bio, wbc->wb->blkcg_css);
291 : : }
292 : :
293 : : #else /* CONFIG_CGROUP_WRITEBACK */
294 : :
295 : : static inline void inode_attach_wb(struct inode *inode, struct page *page)
296 : : {
297 : : }
298 : :
299 : : static inline void inode_detach_wb(struct inode *inode)
300 : : {
301 : : }
302 : :
303 : : static inline void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
304 : : struct inode *inode)
305 : : __releases(&inode->i_lock)
306 : : {
307 : : spin_unlock(&inode->i_lock);
308 : : }
309 : :
310 : : static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
311 : : struct inode *inode)
312 : : {
313 : : }
314 : :
315 : : static inline void wbc_detach_inode(struct writeback_control *wbc)
316 : : {
317 : : }
318 : :
319 : : static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
320 : : {
321 : : }
322 : :
323 : : static inline void wbc_account_cgroup_owner(struct writeback_control *wbc,
324 : : struct page *page, size_t bytes)
325 : : {
326 : : }
327 : :
328 : : static inline void cgroup_writeback_umount(void)
329 : : {
330 : : }
331 : :
332 : : #endif /* CONFIG_CGROUP_WRITEBACK */
333 : :
334 : : /*
335 : : * mm/page-writeback.c
336 : : */
337 : : #ifdef CONFIG_BLOCK
338 : : void laptop_io_completion(struct backing_dev_info *info);
339 : : void laptop_sync_completion(void);
340 : : void laptop_mode_sync(struct work_struct *work);
341 : : void laptop_mode_timer_fn(struct timer_list *t);
342 : : #else
343 : : static inline void laptop_sync_completion(void) { }
344 : : #endif
345 : : bool node_dirty_ok(struct pglist_data *pgdat);
346 : : int wb_domain_init(struct wb_domain *dom, gfp_t gfp);
347 : : #ifdef CONFIG_CGROUP_WRITEBACK
348 : : void wb_domain_exit(struct wb_domain *dom);
349 : : #endif
350 : :
351 : : extern struct wb_domain global_wb_domain;
352 : :
353 : : /* These are exported to sysctl. */
354 : : extern int dirty_background_ratio;
355 : : extern unsigned long dirty_background_bytes;
356 : : extern int vm_dirty_ratio;
357 : : extern unsigned long vm_dirty_bytes;
358 : : extern unsigned int dirty_writeback_interval;
359 : : extern unsigned int dirty_expire_interval;
360 : : extern unsigned int dirtytime_expire_interval;
361 : : extern int vm_highmem_is_dirtyable;
362 : : extern int block_dump;
363 : : extern int laptop_mode;
364 : :
365 : : extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
366 : : void __user *buffer, size_t *lenp,
367 : : loff_t *ppos);
368 : : extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
369 : : void __user *buffer, size_t *lenp,
370 : : loff_t *ppos);
371 : : extern int dirty_ratio_handler(struct ctl_table *table, int write,
372 : : void __user *buffer, size_t *lenp,
373 : : loff_t *ppos);
374 : : extern int dirty_bytes_handler(struct ctl_table *table, int write,
375 : : void __user *buffer, size_t *lenp,
376 : : loff_t *ppos);
377 : : int dirtytime_interval_handler(struct ctl_table *table, int write,
378 : : void __user *buffer, size_t *lenp, loff_t *ppos);
379 : :
380 : : struct ctl_table;
381 : : int dirty_writeback_centisecs_handler(struct ctl_table *, int,
382 : : void __user *, size_t *, loff_t *);
383 : :
384 : : void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
385 : : unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
386 : :
387 : : void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time);
388 : : void balance_dirty_pages_ratelimited(struct address_space *mapping);
389 : : bool wb_over_bg_thresh(struct bdi_writeback *wb);
390 : :
391 : : typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
392 : : void *data);
393 : :
394 : : int generic_writepages(struct address_space *mapping,
395 : : struct writeback_control *wbc);
396 : : void tag_pages_for_writeback(struct address_space *mapping,
397 : : pgoff_t start, pgoff_t end);
398 : : int write_cache_pages(struct address_space *mapping,
399 : : struct writeback_control *wbc, writepage_t writepage,
400 : : void *data);
401 : : int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
402 : : void writeback_set_ratelimit(void);
403 : : void tag_pages_for_writeback(struct address_space *mapping,
404 : : pgoff_t start, pgoff_t end);
405 : :
406 : : void account_page_redirty(struct page *page);
407 : :
408 : : void sb_mark_inode_writeback(struct inode *inode);
409 : : void sb_clear_inode_writeback(struct inode *inode);
410 : :
411 : : #endif /* WRITEBACK_H */
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