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