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 
wbc_to_write_flags(struct writeback_control * wbc)94 static inline blk_opf_t wbc_to_write_flags(struct writeback_control *wbc)
95 {
96 	blk_opf_t flags = 0;
97 
98 	if (wbc->sync_mode == WB_SYNC_ALL)
99 		flags |= REQ_SYNC;
100 	else if (wbc->for_kupdate || wbc->for_background)
101 		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  */
wb_domain_size_changed(struct wb_domain * dom)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. */
wait_on_inode(struct inode * inode)194 static inline void wait_on_inode(struct inode *inode)
195 {
196 	might_sleep();
197 	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  */
inode_attach_wb(struct inode * inode,struct folio * folio)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  */
inode_detach_wb(struct inode * inode)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  */
wbc_attach_fdatawrite_inode(struct writeback_control * wbc,struct inode * inode)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  */
wbc_init_bio(struct writeback_control * wbc,struct bio * bio)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 
inode_attach_wb(struct inode * inode,struct folio * folio)288 static inline void inode_attach_wb(struct inode *inode, struct folio *folio)
289 {
290 }
291 
inode_detach_wb(struct inode * inode)292 static inline void inode_detach_wb(struct inode *inode)
293 {
294 }
295 
wbc_attach_and_unlock_inode(struct writeback_control * wbc,struct inode * inode)296 static inline void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
297 					       struct inode *inode)
298 	__releases(&inode->i_lock)
299 {
300 	spin_unlock(&inode->i_lock);
301 }
302 
wbc_attach_fdatawrite_inode(struct writeback_control * wbc,struct inode * inode)303 static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
304 					       struct inode *inode)
305 {
306 }
307 
wbc_detach_inode(struct writeback_control * wbc)308 static inline void wbc_detach_inode(struct writeback_control *wbc)
309 {
310 }
311 
wbc_init_bio(struct writeback_control * wbc,struct bio * bio)312 static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
313 {
314 }
315 
wbc_account_cgroup_owner(struct writeback_control * wbc,struct page * page,size_t bytes)316 static inline void wbc_account_cgroup_owner(struct writeback_control *wbc,
317 					    struct page *page, size_t bytes)
318 {
319 }
320 
cgroup_writeback_umount(void)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 bool folio_redirty_for_writepage(struct writeback_control *, struct folio *);
379 bool redirty_page_for_writepage(struct writeback_control *, struct page *);
380 
381 void sb_mark_inode_writeback(struct inode *inode);
382 void sb_clear_inode_writeback(struct inode *inode);
383 
384 #endif		/* WRITEBACK_H */
385