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 
wbc_to_write_flags(struct writeback_control * wbc)96 static inline blk_opf_t wbc_to_write_flags(struct writeback_control *wbc)
97 {
98 	blk_opf_t flags = 0;
99 
100 	if (wbc->punt_to_cgroup)
101 		flags = REQ_CGROUP_PUNT;
102 
103 	if (wbc->sync_mode == WB_SYNC_ALL)
104 		flags |= REQ_SYNC;
105 	else if (wbc->for_kupdate || wbc->for_background)
106 		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  */
wb_domain_size_changed(struct wb_domain * dom)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. */
wait_on_inode(struct inode * inode)199 static inline void wait_on_inode(struct inode *inode)
200 {
201 	might_sleep();
202 	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  */
inode_attach_wb(struct inode * inode,struct folio * folio)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  */
inode_detach_wb(struct inode * inode)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  */
wbc_attach_fdatawrite_inode(struct writeback_control * wbc,struct inode * inode)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  */
wbc_init_bio(struct writeback_control * wbc,struct bio * bio)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 
inode_attach_wb(struct inode * inode,struct folio * folio)293 static inline void inode_attach_wb(struct inode *inode, struct folio *folio)
294 {
295 }
296 
inode_detach_wb(struct inode * inode)297 static inline void inode_detach_wb(struct inode *inode)
298 {
299 }
300 
wbc_attach_and_unlock_inode(struct writeback_control * wbc,struct inode * inode)301 static inline void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
302 					       struct inode *inode)
303 	__releases(&inode->i_lock)
304 {
305 	spin_unlock(&inode->i_lock);
306 }
307 
wbc_attach_fdatawrite_inode(struct writeback_control * wbc,struct inode * inode)308 static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
309 					       struct inode *inode)
310 {
311 }
312 
wbc_detach_inode(struct writeback_control * wbc)313 static inline void wbc_detach_inode(struct writeback_control *wbc)
314 {
315 }
316 
wbc_init_bio(struct writeback_control * wbc,struct bio * bio)317 static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
318 {
319 }
320 
wbc_account_cgroup_owner(struct writeback_control * wbc,struct page * page,size_t bytes)321 static inline void wbc_account_cgroup_owner(struct writeback_control *wbc,
322 					    struct page *page, size_t bytes)
323 {
324 }
325 
cgroup_writeback_umount(void)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);
account_page_redirty(struct page * page)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 */
395