projects/linux·blob v5.10-rc1 · refs

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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/blk-cgroup.h>
15
16struct bio;
17
18DECLARE_PER_CPU(int, dirty_throttle_leaks);
19
20/*
21 * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
22 *
23 * (thresh - thresh/DIRTY_FULL_SCOPE, thresh)
24 *
25 * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
26 * time) for the dirty pages to drop, unless written enough pages.
27 *
28 * The global dirty threshold is normally equal to the global dirty limit,
29 * except when the system suddenly allocates a lot of anonymous memory and
30 * knocks down the global dirty threshold quickly, in which case the global
31 * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
32 */
33#define DIRTY_SCOPE 8
34#define DIRTY_FULL_SCOPE (DIRTY_SCOPE / 2)
35
36struct backing_dev_info;
37
38/*
39 * fs/fs-writeback.c
40 */
41enum writeback_sync_modes {
42 WB_SYNC_NONE, /* Don't wait on anything */
43 WB_SYNC_ALL, /* Wait on every mapping */
44};
45
46/*
47 * A control structure which tells the writeback code what to do. These are
48 * always on the stack, and hence need no locking. They are always initialised
49 * in a manner such that unspecified fields are set to zero.
50 */
51struct writeback_control {
52 long nr_to_write; /* Write this many pages, and decrement
53 this for each page written */
54 long pages_skipped; /* Pages which were not written */
55
56 /*
57 * For a_ops->writepages(): if start or end are non-zero then this is
58 * a hint that the filesystem need only write out the pages inside that
59 * byterange. The byte at `end' is included in the writeout request.
60 */
61 loff_t range_start;
62 loff_t range_end;
63
64 enum writeback_sync_modes sync_mode;
65
66 unsigned for_kupdate:1; /* A kupdate writeback */
67 unsigned for_background:1; /* A background writeback */
68 unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */
69 unsigned for_reclaim:1; /* Invoked from the page allocator */
70 unsigned range_cyclic:1; /* range_start is cyclic */
71 unsigned for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
72
73 /*
74 * When writeback IOs are bounced through async layers, only the
75 * initial synchronous phase should be accounted towards inode
76 * cgroup ownership arbitration to avoid confusion. Later stages
77 * can set the following flag to disable the accounting.
78 */
79 unsigned no_cgroup_owner:1;
80
81 unsigned punt_to_cgroup:1; /* cgrp punting, see __REQ_CGROUP_PUNT */
82
83#ifdef CONFIG_CGROUP_WRITEBACK
84 struct bdi_writeback *wb; /* wb this writeback is issued under */
85 struct inode *inode; /* inode being written out */
86
87 /* foreign inode detection, see wbc_detach_inode() */
88 int wb_id; /* current wb id */
89 int wb_lcand_id; /* last foreign candidate wb id */
90 int wb_tcand_id; /* this foreign candidate wb id */
91 size_t wb_bytes; /* bytes written by current wb */
92 size_t wb_lcand_bytes; /* bytes written by last candidate */
93 size_t wb_tcand_bytes; /* bytes written by this candidate */
94#endif
95};
96
97static inline int wbc_to_write_flags(struct writeback_control *wbc)
98{
99 int flags = 0;
100
101 if (wbc->punt_to_cgroup)
102 flags = REQ_CGROUP_PUNT;
103
104 if (wbc->sync_mode == WB_SYNC_ALL)
105 flags |= REQ_SYNC;
106 else if (wbc->for_kupdate || wbc->for_background)
107 flags |= REQ_BACKGROUND;
108
109 return flags;
110}
111
112static inline struct cgroup_subsys_state *
113wbc_blkcg_css(struct writeback_control *wbc)
114{
115#ifdef CONFIG_CGROUP_WRITEBACK
116 if (wbc->wb)
117 return wbc->wb->blkcg_css;
118#endif
119 return blkcg_root_css;
120}
121
122/*
123 * A wb_domain represents a domain that wb's (bdi_writeback's) belong to
124 * and are measured against each other in. There always is one global
125 * domain, global_wb_domain, that every wb in the system is a member of.
126 * This allows measuring the relative bandwidth of each wb to distribute
127 * dirtyable memory accordingly.
128 */
129struct wb_domain {
130 spinlock_t lock;
131
132 /*
133 * Scale the writeback cache size proportional to the relative
134 * writeout speed.
135 *
136 * We do this by keeping a floating proportion between BDIs, based
137 * on page writeback completions [end_page_writeback()]. Those
138 * devices that write out pages fastest will get the larger share,
139 * while the slower will get a smaller share.
140 *
141 * We use page writeout completions because we are interested in
142 * getting rid of dirty pages. Having them written out is the
143 * primary goal.
144 *
145 * We introduce a concept of time, a period over which we measure
146 * these events, because demand can/will vary over time. The length
147 * of this period itself is measured in page writeback completions.
148 */
149 struct fprop_global completions;
150 struct timer_list period_timer; /* timer for aging of completions */
151 unsigned long period_time;
152
153 /*
154 * The dirtyable memory and dirty threshold could be suddenly
155 * knocked down by a large amount (eg. on the startup of KVM in a
156 * swapless system). This may throw the system into deep dirty
157 * exceeded state and throttle heavy/light dirtiers alike. To
158 * retain good responsiveness, maintain global_dirty_limit for
159 * tracking slowly down to the knocked down dirty threshold.
160 *
161 * Both fields are protected by ->lock.
162 */
163 unsigned long dirty_limit_tstamp;
164 unsigned long dirty_limit;
165};
166
167/**
168 * wb_domain_size_changed - memory available to a wb_domain has changed
169 * @dom: wb_domain of interest
170 *
171 * This function should be called when the amount of memory available to
172 * @dom has changed. It resets @dom's dirty limit parameters to prevent
173 * the past values which don't match the current configuration from skewing
174 * dirty throttling. Without this, when memory size of a wb_domain is
175 * greatly reduced, the dirty throttling logic may allow too many pages to
176 * be dirtied leading to consecutive unnecessary OOMs and may get stuck in
177 * that situation.
178 */
179static inline void wb_domain_size_changed(struct wb_domain *dom)
180{
181 spin_lock(&dom->lock);
182 dom->dirty_limit_tstamp = jiffies;
183 dom->dirty_limit = 0;
184 spin_unlock(&dom->lock);
185}
186
187/*
188 * fs/fs-writeback.c
189 */
190struct bdi_writeback;
191void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
192void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
193 enum wb_reason reason);
194void try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason);
195void sync_inodes_sb(struct super_block *);
196void wakeup_flusher_threads(enum wb_reason reason);
197void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
198 enum wb_reason reason);
199void inode_wait_for_writeback(struct inode *inode);
200void inode_io_list_del(struct inode *inode);
201
202/* writeback.h requires fs.h; it, too, is not included from here. */
203static inline void wait_on_inode(struct inode *inode)
204{
205 might_sleep();
206 wait_on_bit(&inode->i_state, __I_NEW, TASK_UNINTERRUPTIBLE);
207}
208
209#ifdef CONFIG_CGROUP_WRITEBACK
210
211#include <linux/cgroup.h>
212#include <linux/bio.h>
213
214void __inode_attach_wb(struct inode *inode, struct page *page);
215void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
216 struct inode *inode)
217 __releases(&inode->i_lock);
218void wbc_detach_inode(struct writeback_control *wbc);
219void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
220 size_t bytes);
221int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr_pages,
222 enum wb_reason reason, struct wb_completion *done);
223void cgroup_writeback_umount(void);
224
225/**
226 * inode_attach_wb - associate an inode with its wb
227 * @inode: inode of interest
228 * @page: page being dirtied (may be NULL)
229 *
230 * If @inode doesn't have its wb, associate it with the wb matching the
231 * memcg of @page or, if @page is NULL, %current. May be called w/ or w/o
232 * @inode->i_lock.
233 */
234static inline void inode_attach_wb(struct inode *inode, struct page *page)
235{
236 if (!inode->i_wb)
237 __inode_attach_wb(inode, page);
238}
239
240/**
241 * inode_detach_wb - disassociate an inode from its wb
242 * @inode: inode of interest
243 *
244 * @inode is being freed. Detach from its wb.
245 */
246static inline void inode_detach_wb(struct inode *inode)
247{
248 if (inode->i_wb) {
249 WARN_ON_ONCE(!(inode->i_state & I_CLEAR));
250 wb_put(inode->i_wb);
251 inode->i_wb = NULL;
252 }
253}
254
255/**
256 * wbc_attach_fdatawrite_inode - associate wbc and inode for fdatawrite
257 * @wbc: writeback_control of interest
258 * @inode: target inode
259 *
260 * This function is to be used by __filemap_fdatawrite_range(), which is an
261 * alternative entry point into writeback code, and first ensures @inode is
262 * associated with a bdi_writeback and attaches it to @wbc.
263 */
264static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
265 struct inode *inode)
266{
267 spin_lock(&inode->i_lock);
268 inode_attach_wb(inode, NULL);
269 wbc_attach_and_unlock_inode(wbc, inode);
270}
271
272/**
273 * wbc_init_bio - writeback specific initializtion of bio
274 * @wbc: writeback_control for the writeback in progress
275 * @bio: bio to be initialized
276 *
277 * @bio is a part of the writeback in progress controlled by @wbc. Perform
278 * writeback specific initialization. This is used to apply the cgroup
279 * writeback context. Must be called after the bio has been associated with
280 * a device.
281 */
282static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
283{
284 /*
285 * pageout() path doesn't attach @wbc to the inode being written
286 * out. This is intentional as we don't want the function to block
287 * behind a slow cgroup. Ultimately, we want pageout() to kick off
288 * regular writeback instead of writing things out itself.
289 */
290 if (wbc->wb)
291 bio_associate_blkg_from_css(bio, wbc->wb->blkcg_css);
292}
293
294#else /* CONFIG_CGROUP_WRITEBACK */
295
296static inline void inode_attach_wb(struct inode *inode, struct page *page)
297{
298}
299
300static inline void inode_detach_wb(struct inode *inode)
301{
302}
303
304static inline void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
305 struct inode *inode)
306 __releases(&inode->i_lock)
307{
308 spin_unlock(&inode->i_lock);
309}
310
311static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
312 struct inode *inode)
313{
314}
315
316static inline void wbc_detach_inode(struct writeback_control *wbc)
317{
318}
319
320static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
321{
322}
323
324static inline void wbc_account_cgroup_owner(struct writeback_control *wbc,
325 struct page *page, size_t bytes)
326{
327}
328
329static inline void cgroup_writeback_umount(void)
330{
331}
332
333#endif /* CONFIG_CGROUP_WRITEBACK */
334
335/*
336 * mm/page-writeback.c
337 */
338#ifdef CONFIG_BLOCK
339void laptop_io_completion(struct backing_dev_info *info);
340void laptop_sync_completion(void);
341void laptop_mode_sync(struct work_struct *work);
342void laptop_mode_timer_fn(struct timer_list *t);
343#else
344static inline void laptop_sync_completion(void) { }
345#endif
346bool node_dirty_ok(struct pglist_data *pgdat);
347int wb_domain_init(struct wb_domain *dom, gfp_t gfp);
348#ifdef CONFIG_CGROUP_WRITEBACK
349void wb_domain_exit(struct wb_domain *dom);
350#endif
351
352extern struct wb_domain global_wb_domain;
353
354/* These are exported to sysctl. */
355extern int dirty_background_ratio;
356extern unsigned long dirty_background_bytes;
357extern int vm_dirty_ratio;
358extern unsigned long vm_dirty_bytes;
359extern unsigned int dirty_writeback_interval;
360extern unsigned int dirty_expire_interval;
361extern unsigned int dirtytime_expire_interval;
362extern int vm_highmem_is_dirtyable;
363extern int block_dump;
364extern int laptop_mode;
365
366int dirty_background_ratio_handler(struct ctl_table *table, int write,
367 void *buffer, size_t *lenp, loff_t *ppos);
368int dirty_background_bytes_handler(struct ctl_table *table, int write,
369 void *buffer, size_t *lenp, loff_t *ppos);
370int dirty_ratio_handler(struct ctl_table *table, int write,
371 void *buffer, size_t *lenp, loff_t *ppos);
372int dirty_bytes_handler(struct ctl_table *table, int write,
373 void *buffer, size_t *lenp, loff_t *ppos);
374int dirtytime_interval_handler(struct ctl_table *table, int write,
375 void *buffer, size_t *lenp, loff_t *ppos);
376int dirty_writeback_centisecs_handler(struct ctl_table *table, int write,
377 void *buffer, size_t *lenp, loff_t *ppos);
378
379void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
380unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
381
382void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time);
383void balance_dirty_pages_ratelimited(struct address_space *mapping);
384bool wb_over_bg_thresh(struct bdi_writeback *wb);
385
386typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
387 void *data);
388
389int generic_writepages(struct address_space *mapping,
390 struct writeback_control *wbc);
391void tag_pages_for_writeback(struct address_space *mapping,
392 pgoff_t start, pgoff_t end);
393int write_cache_pages(struct address_space *mapping,
394 struct writeback_control *wbc, writepage_t writepage,
395 void *data);
396int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
397void writeback_set_ratelimit(void);
398void tag_pages_for_writeback(struct address_space *mapping,
399 pgoff_t start, pgoff_t end);
400
401void account_page_redirty(struct page *page);
402
403void sb_mark_inode_writeback(struct inode *inode);
404void sb_clear_inode_writeback(struct inode *inode);
405
406#endif /* WRITEBACK_H */