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 :
15 : struct bio;
16 :
17 : DECLARE_PER_CPU(int, dirty_throttle_leaks);
18 :
19 : /*
20 : * The global dirty threshold is normally equal to the global dirty limit,
21 : * except when the system suddenly allocates a lot of anonymous memory and
22 : * knocks down the global dirty threshold quickly, in which case the global
23 : * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
24 : */
25 : #define DIRTY_SCOPE 8
26 :
27 : struct backing_dev_info;
28 :
29 : /*
30 : * fs/fs-writeback.c
31 : */
32 : enum writeback_sync_modes {
33 : WB_SYNC_NONE, /* Don't wait on anything */
34 : WB_SYNC_ALL, /* Wait on every mapping */
35 : };
36 :
37 : /*
38 : * A control structure which tells the writeback code what to do. These are
39 : * always on the stack, and hence need no locking. They are always initialised
40 : * in a manner such that unspecified fields are set to zero.
41 : */
42 : struct writeback_control {
43 : long nr_to_write; /* Write this many pages, and decrement
44 : this for each page written */
45 : long pages_skipped; /* Pages which were not written */
46 :
47 : /*
48 : * For a_ops->writepages(): if start or end are non-zero then this is
49 : * a hint that the filesystem need only write out the pages inside that
50 : * byterange. The byte at `end' is included in the writeout request.
51 : */
52 : loff_t range_start;
53 : loff_t range_end;
54 :
55 : enum writeback_sync_modes sync_mode;
56 :
57 : unsigned for_kupdate:1; /* A kupdate writeback */
58 : unsigned for_background:1; /* A background writeback */
59 : unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */
60 : unsigned for_reclaim:1; /* Invoked from the page allocator */
61 : unsigned range_cyclic:1; /* range_start is cyclic */
62 : unsigned for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
63 : unsigned unpinned_fscache_wb:1; /* Cleared I_PINNING_FSCACHE_WB */
64 :
65 : /*
66 : * When writeback IOs are bounced through async layers, only the
67 : * initial synchronous phase should be accounted towards inode
68 : * cgroup ownership arbitration to avoid confusion. Later stages
69 : * can set the following flag to disable the accounting.
70 : */
71 : unsigned no_cgroup_owner:1;
72 :
73 : unsigned punt_to_cgroup:1; /* cgrp punting, see __REQ_CGROUP_PUNT */
74 :
75 : /* To enable batching of swap writes to non-block-device backends,
76 : * "plug" can be set point to a 'struct swap_iocb *'. When all swap
77 : * writes have been submitted, if with swap_iocb is not NULL,
78 : * swap_write_unplug() should be called.
79 : */
80 : struct swap_iocb **swap_plug;
81 :
82 : #ifdef CONFIG_CGROUP_WRITEBACK
83 : struct bdi_writeback *wb; /* wb this writeback is issued under */
84 : struct inode *inode; /* inode being written out */
85 :
86 : /* foreign inode detection, see wbc_detach_inode() */
87 : int wb_id; /* current wb id */
88 : int wb_lcand_id; /* last foreign candidate wb id */
89 : int wb_tcand_id; /* this foreign candidate wb id */
90 : size_t wb_bytes; /* bytes written by current wb */
91 : size_t wb_lcand_bytes; /* bytes written by last candidate */
92 : size_t wb_tcand_bytes; /* bytes written by this candidate */
93 : #endif
94 : };
95 :
96 : static inline blk_opf_t wbc_to_write_flags(struct writeback_control *wbc)
97 : {
98 0 : blk_opf_t flags = 0;
99 :
100 0 : if (wbc->punt_to_cgroup)
101 0 : flags = REQ_CGROUP_PUNT;
102 :
103 0 : if (wbc->sync_mode == WB_SYNC_ALL)
104 0 : flags |= REQ_SYNC;
105 0 : else if (wbc->for_kupdate || wbc->for_background)
106 0 : flags |= REQ_BACKGROUND;
107 :
108 : return flags;
109 : }
110 :
111 : #ifdef CONFIG_CGROUP_WRITEBACK
112 : #define wbc_blkcg_css(wbc) \
113 : ((wbc)->wb ? (wbc)->wb->blkcg_css : blkcg_root_css)
114 : #else
115 : #define wbc_blkcg_css(wbc) (blkcg_root_css)
116 : #endif /* CONFIG_CGROUP_WRITEBACK */
117 :
118 : /*
119 : * A wb_domain represents a domain that wb's (bdi_writeback's) belong to
120 : * and are measured against each other in. There always is one global
121 : * domain, global_wb_domain, that every wb in the system is a member of.
122 : * This allows measuring the relative bandwidth of each wb to distribute
123 : * dirtyable memory accordingly.
124 : */
125 : struct wb_domain {
126 : spinlock_t lock;
127 :
128 : /*
129 : * Scale the writeback cache size proportional to the relative
130 : * writeout speed.
131 : *
132 : * We do this by keeping a floating proportion between BDIs, based
133 : * on page writeback completions [end_page_writeback()]. Those
134 : * devices that write out pages fastest will get the larger share,
135 : * while the slower will get a smaller share.
136 : *
137 : * We use page writeout completions because we are interested in
138 : * getting rid of dirty pages. Having them written out is the
139 : * primary goal.
140 : *
141 : * We introduce a concept of time, a period over which we measure
142 : * these events, because demand can/will vary over time. The length
143 : * of this period itself is measured in page writeback completions.
144 : */
145 : struct fprop_global completions;
146 : struct timer_list period_timer; /* timer for aging of completions */
147 : unsigned long period_time;
148 :
149 : /*
150 : * The dirtyable memory and dirty threshold could be suddenly
151 : * knocked down by a large amount (eg. on the startup of KVM in a
152 : * swapless system). This may throw the system into deep dirty
153 : * exceeded state and throttle heavy/light dirtiers alike. To
154 : * retain good responsiveness, maintain global_dirty_limit for
155 : * tracking slowly down to the knocked down dirty threshold.
156 : *
157 : * Both fields are protected by ->lock.
158 : */
159 : unsigned long dirty_limit_tstamp;
160 : unsigned long dirty_limit;
161 : };
162 :
163 : /**
164 : * wb_domain_size_changed - memory available to a wb_domain has changed
165 : * @dom: wb_domain of interest
166 : *
167 : * This function should be called when the amount of memory available to
168 : * @dom has changed. It resets @dom's dirty limit parameters to prevent
169 : * the past values which don't match the current configuration from skewing
170 : * dirty throttling. Without this, when memory size of a wb_domain is
171 : * greatly reduced, the dirty throttling logic may allow too many pages to
172 : * be dirtied leading to consecutive unnecessary OOMs and may get stuck in
173 : * that situation.
174 : */
175 : static inline void wb_domain_size_changed(struct wb_domain *dom)
176 : {
177 : spin_lock(&dom->lock);
178 : dom->dirty_limit_tstamp = jiffies;
179 : dom->dirty_limit = 0;
180 : spin_unlock(&dom->lock);
181 : }
182 :
183 : /*
184 : * fs/fs-writeback.c
185 : */
186 : struct bdi_writeback;
187 : void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
188 : void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
189 : enum wb_reason reason);
190 : void try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason);
191 : void sync_inodes_sb(struct super_block *);
192 : void wakeup_flusher_threads(enum wb_reason reason);
193 : void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
194 : enum wb_reason reason);
195 : void inode_wait_for_writeback(struct inode *inode);
196 : void inode_io_list_del(struct inode *inode);
197 :
198 : /* writeback.h requires fs.h; it, too, is not included from here. */
199 : static inline void wait_on_inode(struct inode *inode)
200 : {
201 : might_sleep();
202 0 : wait_on_bit(&inode->i_state, __I_NEW, TASK_UNINTERRUPTIBLE);
203 : }
204 :
205 : #ifdef CONFIG_CGROUP_WRITEBACK
206 :
207 : #include <linux/cgroup.h>
208 : #include <linux/bio.h>
209 :
210 : void __inode_attach_wb(struct inode *inode, struct folio *folio);
211 : void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
212 : struct inode *inode)
213 : __releases(&inode->i_lock);
214 : void wbc_detach_inode(struct writeback_control *wbc);
215 : void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
216 : size_t bytes);
217 : int cgroup_writeback_by_id(u64 bdi_id, int memcg_id,
218 : enum wb_reason reason, struct wb_completion *done);
219 : void cgroup_writeback_umount(void);
220 : bool cleanup_offline_cgwb(struct bdi_writeback *wb);
221 :
222 : /**
223 : * inode_attach_wb - associate an inode with its wb
224 : * @inode: inode of interest
225 : * @folio: folio being dirtied (may be NULL)
226 : *
227 : * If @inode doesn't have its wb, associate it with the wb matching the
228 : * memcg of @folio or, if @folio is NULL, %current. May be called w/ or w/o
229 : * @inode->i_lock.
230 : */
231 : static inline void inode_attach_wb(struct inode *inode, struct folio *folio)
232 : {
233 : if (!inode->i_wb)
234 : __inode_attach_wb(inode, folio);
235 : }
236 :
237 : /**
238 : * inode_detach_wb - disassociate an inode from its wb
239 : * @inode: inode of interest
240 : *
241 : * @inode is being freed. Detach from its wb.
242 : */
243 : static inline void inode_detach_wb(struct inode *inode)
244 : {
245 : if (inode->i_wb) {
246 : WARN_ON_ONCE(!(inode->i_state & I_CLEAR));
247 : wb_put(inode->i_wb);
248 : inode->i_wb = NULL;
249 : }
250 : }
251 :
252 : /**
253 : * wbc_attach_fdatawrite_inode - associate wbc and inode for fdatawrite
254 : * @wbc: writeback_control of interest
255 : * @inode: target inode
256 : *
257 : * This function is to be used by __filemap_fdatawrite_range(), which is an
258 : * alternative entry point into writeback code, and first ensures @inode is
259 : * associated with a bdi_writeback and attaches it to @wbc.
260 : */
261 : static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
262 : struct inode *inode)
263 : {
264 : spin_lock(&inode->i_lock);
265 : inode_attach_wb(inode, NULL);
266 : wbc_attach_and_unlock_inode(wbc, inode);
267 : }
268 :
269 : /**
270 : * wbc_init_bio - writeback specific initializtion of bio
271 : * @wbc: writeback_control for the writeback in progress
272 : * @bio: bio to be initialized
273 : *
274 : * @bio is a part of the writeback in progress controlled by @wbc. Perform
275 : * writeback specific initialization. This is used to apply the cgroup
276 : * writeback context. Must be called after the bio has been associated with
277 : * a device.
278 : */
279 : static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
280 : {
281 : /*
282 : * pageout() path doesn't attach @wbc to the inode being written
283 : * out. This is intentional as we don't want the function to block
284 : * behind a slow cgroup. Ultimately, we want pageout() to kick off
285 : * regular writeback instead of writing things out itself.
286 : */
287 : if (wbc->wb)
288 : bio_associate_blkg_from_css(bio, wbc->wb->blkcg_css);
289 : }
290 :
291 : #else /* CONFIG_CGROUP_WRITEBACK */
292 :
293 : static inline void inode_attach_wb(struct inode *inode, struct folio *folio)
294 : {
295 : }
296 :
297 : static inline void inode_detach_wb(struct inode *inode)
298 : {
299 : }
300 :
301 : static inline void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
302 : struct inode *inode)
303 : __releases(&inode->i_lock)
304 : {
305 0 : spin_unlock(&inode->i_lock);
306 : }
307 :
308 : static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
309 : struct inode *inode)
310 : {
311 : }
312 :
313 : static inline void wbc_detach_inode(struct writeback_control *wbc)
314 : {
315 : }
316 :
317 : static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
318 : {
319 : }
320 :
321 : static inline void wbc_account_cgroup_owner(struct writeback_control *wbc,
322 : struct page *page, size_t bytes)
323 : {
324 : }
325 :
326 : static inline void cgroup_writeback_umount(void)
327 : {
328 : }
329 :
330 : #endif /* CONFIG_CGROUP_WRITEBACK */
331 :
332 : /*
333 : * mm/page-writeback.c
334 : */
335 : void laptop_io_completion(struct backing_dev_info *info);
336 : void laptop_sync_completion(void);
337 : void laptop_mode_timer_fn(struct timer_list *t);
338 : bool node_dirty_ok(struct pglist_data *pgdat);
339 : int wb_domain_init(struct wb_domain *dom, gfp_t gfp);
340 : #ifdef CONFIG_CGROUP_WRITEBACK
341 : void wb_domain_exit(struct wb_domain *dom);
342 : #endif
343 :
344 : extern struct wb_domain global_wb_domain;
345 :
346 : /* These are exported to sysctl. */
347 : extern unsigned int dirty_writeback_interval;
348 : extern unsigned int dirty_expire_interval;
349 : extern unsigned int dirtytime_expire_interval;
350 : extern int laptop_mode;
351 :
352 : int dirtytime_interval_handler(struct ctl_table *table, int write,
353 : void *buffer, size_t *lenp, loff_t *ppos);
354 :
355 : void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
356 : unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
357 :
358 : void wb_update_bandwidth(struct bdi_writeback *wb);
359 :
360 : /* Invoke balance dirty pages in async mode. */
361 : #define BDP_ASYNC 0x0001
362 :
363 : void balance_dirty_pages_ratelimited(struct address_space *mapping);
364 : int balance_dirty_pages_ratelimited_flags(struct address_space *mapping,
365 : unsigned int flags);
366 :
367 : bool wb_over_bg_thresh(struct bdi_writeback *wb);
368 :
369 : typedef int (*writepage_t)(struct folio *folio, struct writeback_control *wbc,
370 : void *data);
371 :
372 : void tag_pages_for_writeback(struct address_space *mapping,
373 : pgoff_t start, pgoff_t end);
374 : int write_cache_pages(struct address_space *mapping,
375 : struct writeback_control *wbc, writepage_t writepage,
376 : void *data);
377 : int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
378 : void writeback_set_ratelimit(void);
379 : void tag_pages_for_writeback(struct address_space *mapping,
380 : pgoff_t start, pgoff_t end);
381 :
382 : bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio);
383 : void folio_account_redirty(struct folio *folio);
384 : static inline void account_page_redirty(struct page *page)
385 : {
386 : folio_account_redirty(page_folio(page));
387 : }
388 : bool folio_redirty_for_writepage(struct writeback_control *, struct folio *);
389 : bool redirty_page_for_writepage(struct writeback_control *, struct page *);
390 :
391 : void sb_mark_inode_writeback(struct inode *inode);
392 : void sb_clear_inode_writeback(struct inode *inode);
393 :
394 : #endif /* WRITEBACK_H */
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