Line data Source code
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 :
97 872 : static inline int wbc_to_write_flags(struct writeback_control *wbc)
98 : {
99 872 : int flags = 0;
100 :
101 872 : if (wbc->punt_to_cgroup)
102 0 : flags = REQ_CGROUP_PUNT;
103 :
104 872 : if (wbc->sync_mode == WB_SYNC_ALL)
105 0 : flags |= REQ_SYNC;
106 872 : else if (wbc->for_kupdate || wbc->for_background)
107 872 : flags |= REQ_BACKGROUND;
108 :
109 872 : 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 : static inline void wb_domain_size_changed(struct wb_domain *dom)
180 : {
181 : spin_lock(&dom->lock);
182 : dom->dirty_limit_tstamp = jiffies;
183 : dom->dirty_limit = 0;
184 : spin_unlock(&dom->lock);
185 : }
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 : void inode_io_list_del(struct inode *inode);
201 :
202 : /* writeback.h requires fs.h; it, too, is not included from here. */
203 407 : static inline void wait_on_inode(struct inode *inode)
204 : {
205 407 : might_sleep();
206 407 : wait_on_bit(&inode->i_state, __I_NEW, TASK_UNINTERRUPTIBLE);
207 407 : }
208 :
209 : #ifdef CONFIG_CGROUP_WRITEBACK
210 :
211 : #include <linux/cgroup.h>
212 : #include <linux/bio.h>
213 :
214 : void __inode_attach_wb(struct inode *inode, struct page *page);
215 : void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
216 : struct inode *inode)
217 : __releases(&inode->i_lock);
218 : void wbc_detach_inode(struct writeback_control *wbc);
219 : void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
220 : size_t bytes);
221 : int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr_pages,
222 : enum wb_reason reason, struct wb_completion *done);
223 : void cgroup_writeback_umount(void);
224 :
225 : /**
226 : * inode_attach_wb - associate an inode with its wb
227 : * @inode: inode of interest
228 : * @page: page being dirtied (may be NULL)
229 : *
230 : * If @inode doesn't have its wb, associate it with the wb matching the
231 : * memcg of @page or, if @page is NULL, %current. May be called w/ or w/o
232 : * @inode->i_lock.
233 : */
234 : static inline void inode_attach_wb(struct inode *inode, struct page *page)
235 : {
236 : if (!inode->i_wb)
237 : __inode_attach_wb(inode, page);
238 : }
239 :
240 : /**
241 : * inode_detach_wb - disassociate an inode from its wb
242 : * @inode: inode of interest
243 : *
244 : * @inode is being freed. Detach from its wb.
245 : */
246 : static inline void inode_detach_wb(struct inode *inode)
247 : {
248 : if (inode->i_wb) {
249 : WARN_ON_ONCE(!(inode->i_state & I_CLEAR));
250 : wb_put(inode->i_wb);
251 : inode->i_wb = NULL;
252 : }
253 : }
254 :
255 : /**
256 : * wbc_attach_fdatawrite_inode - associate wbc and inode for fdatawrite
257 : * @wbc: writeback_control of interest
258 : * @inode: target inode
259 : *
260 : * This function is to be used by __filemap_fdatawrite_range(), which is an
261 : * alternative entry point into writeback code, and first ensures @inode is
262 : * associated with a bdi_writeback and attaches it to @wbc.
263 : */
264 : static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
265 : struct inode *inode)
266 : {
267 : spin_lock(&inode->i_lock);
268 : inode_attach_wb(inode, NULL);
269 : wbc_attach_and_unlock_inode(wbc, inode);
270 : }
271 :
272 : /**
273 : * wbc_init_bio - writeback specific initializtion of bio
274 : * @wbc: writeback_control for the writeback in progress
275 : * @bio: bio to be initialized
276 : *
277 : * @bio is a part of the writeback in progress controlled by @wbc. Perform
278 : * writeback specific initialization. This is used to apply the cgroup
279 : * writeback context. Must be called after the bio has been associated with
280 : * a device.
281 : */
282 : static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
283 : {
284 : /*
285 : * pageout() path doesn't attach @wbc to the inode being written
286 : * out. This is intentional as we don't want the function to block
287 : * behind a slow cgroup. Ultimately, we want pageout() to kick off
288 : * regular writeback instead of writing things out itself.
289 : */
290 : if (wbc->wb)
291 : bio_associate_blkg_from_css(bio, wbc->wb->blkcg_css);
292 : }
293 :
294 : #else /* CONFIG_CGROUP_WRITEBACK */
295 :
296 5724 : static inline void inode_attach_wb(struct inode *inode, struct page *page)
297 : {
298 5724 : }
299 :
300 5288 : static inline void inode_detach_wb(struct inode *inode)
301 : {
302 5288 : }
303 :
304 1374 : static inline void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
305 : struct inode *inode)
306 : __releases(&inode->i_lock)
307 : {
308 1374 : spin_unlock(&inode->i_lock);
309 : }
310 :
311 0 : static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
312 : struct inode *inode)
313 : {
314 0 : }
315 :
316 1374 : static inline void wbc_detach_inode(struct writeback_control *wbc)
317 : {
318 1374 : }
319 :
320 116 : static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
321 : {
322 116 : }
323 :
324 514 : static inline void wbc_account_cgroup_owner(struct writeback_control *wbc,
325 : struct page *page, size_t bytes)
326 : {
327 514 : }
328 :
329 98 : static inline void cgroup_writeback_umount(void)
330 : {
331 98 : }
332 :
333 : #endif /* CONFIG_CGROUP_WRITEBACK */
334 :
335 : /*
336 : * mm/page-writeback.c
337 : */
338 : #ifdef CONFIG_BLOCK
339 : void laptop_io_completion(struct backing_dev_info *info);
340 : void laptop_sync_completion(void);
341 : void laptop_mode_sync(struct work_struct *work);
342 : void laptop_mode_timer_fn(struct timer_list *t);
343 : #else
344 : static inline void laptop_sync_completion(void) { }
345 : #endif
346 : bool node_dirty_ok(struct pglist_data *pgdat);
347 : int wb_domain_init(struct wb_domain *dom, gfp_t gfp);
348 : #ifdef CONFIG_CGROUP_WRITEBACK
349 : void wb_domain_exit(struct wb_domain *dom);
350 : #endif
351 :
352 : extern struct wb_domain global_wb_domain;
353 :
354 : /* These are exported to sysctl. */
355 : extern int dirty_background_ratio;
356 : extern unsigned long dirty_background_bytes;
357 : extern int vm_dirty_ratio;
358 : extern unsigned long vm_dirty_bytes;
359 : extern unsigned int dirty_writeback_interval;
360 : extern unsigned int dirty_expire_interval;
361 : extern unsigned int dirtytime_expire_interval;
362 : extern int vm_highmem_is_dirtyable;
363 : extern int block_dump;
364 : extern int laptop_mode;
365 :
366 : int dirty_background_ratio_handler(struct ctl_table *table, int write,
367 : void *buffer, size_t *lenp, loff_t *ppos);
368 : int dirty_background_bytes_handler(struct ctl_table *table, int write,
369 : void *buffer, size_t *lenp, loff_t *ppos);
370 : int dirty_ratio_handler(struct ctl_table *table, int write,
371 : void *buffer, size_t *lenp, loff_t *ppos);
372 : int dirty_bytes_handler(struct ctl_table *table, int write,
373 : void *buffer, size_t *lenp, loff_t *ppos);
374 : int dirtytime_interval_handler(struct ctl_table *table, int write,
375 : void *buffer, size_t *lenp, loff_t *ppos);
376 : int dirty_writeback_centisecs_handler(struct ctl_table *table, int write,
377 : void *buffer, size_t *lenp, loff_t *ppos);
378 :
379 : void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
380 : unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
381 :
382 : void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time);
383 : void balance_dirty_pages_ratelimited(struct address_space *mapping);
384 : bool wb_over_bg_thresh(struct bdi_writeback *wb);
385 :
386 : typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
387 : void *data);
388 :
389 : int generic_writepages(struct address_space *mapping,
390 : struct writeback_control *wbc);
391 : void tag_pages_for_writeback(struct address_space *mapping,
392 : pgoff_t start, pgoff_t end);
393 : int write_cache_pages(struct address_space *mapping,
394 : struct writeback_control *wbc, writepage_t writepage,
395 : void *data);
396 : int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
397 : void writeback_set_ratelimit(void);
398 : void tag_pages_for_writeback(struct address_space *mapping,
399 : pgoff_t start, pgoff_t end);
400 :
401 : void account_page_redirty(struct page *page);
402 :
403 : void sb_mark_inode_writeback(struct inode *inode);
404 : void sb_clear_inode_writeback(struct inode *inode);
405 :
406 : #endif /* WRITEBACK_H */
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