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