[go: up one dir, main page]
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
16struct bio;
17
18DECLARE_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
28struct backing_dev_info;
29
30/*
31 * fs/fs-writeback.c
32 */
33enum 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 */
43struct 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 range_cyclic:1; /* range_start is cyclic */
63 unsigned for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
64 unsigned unpinned_netfs_wb:1; /* Cleared I_PINNING_NETFS_WB */
65
66 /*
67 * When writeback IOs are bounced through async layers, only the
68 * initial synchronous phase should be accounted towards inode
69 * cgroup ownership arbitration to avoid confusion. Later stages
70 * can set the following flag to disable the accounting.
71 */
72 unsigned no_cgroup_owner:1;
73
74 /* internal fields used by the ->writepages implementation: */
75 struct folio_batch fbatch;
76 pgoff_t index;
77 int saved_err;
78
79#ifdef CONFIG_CGROUP_WRITEBACK
80 struct bdi_writeback *wb; /* wb this writeback is issued under */
81 struct inode *inode; /* inode being written out */
82
83 /* foreign inode detection, see wbc_detach_inode() */
84 int wb_id; /* current wb id */
85 int wb_lcand_id; /* last foreign candidate wb id */
86 int wb_tcand_id; /* this foreign candidate wb id */
87 size_t wb_bytes; /* bytes written by current wb */
88 size_t wb_lcand_bytes; /* bytes written by last candidate */
89 size_t wb_tcand_bytes; /* bytes written by this candidate */
90#endif
91};
92
93static inline blk_opf_t wbc_to_write_flags(struct writeback_control *wbc)
94{
95 blk_opf_t flags = 0;
96
97 if (wbc->sync_mode == WB_SYNC_ALL)
98 flags |= REQ_SYNC;
99 else if (wbc->for_kupdate || wbc->for_background)
100 flags |= REQ_BACKGROUND;
101
102 return flags;
103}
104
105#ifdef CONFIG_CGROUP_WRITEBACK
106#define wbc_blkcg_css(wbc) \
107 ((wbc)->wb ? (wbc)->wb->blkcg_css : blkcg_root_css)
108#else
109#define wbc_blkcg_css(wbc) (blkcg_root_css)
110#endif /* CONFIG_CGROUP_WRITEBACK */
111
112/*
113 * A wb_domain represents a domain that wb's (bdi_writeback's) belong to
114 * and are measured against each other in. There always is one global
115 * domain, global_wb_domain, that every wb in the system is a member of.
116 * This allows measuring the relative bandwidth of each wb to distribute
117 * dirtyable memory accordingly.
118 */
119struct wb_domain {
120 spinlock_t lock;
121
122 /*
123 * Scale the writeback cache size proportional to the relative
124 * writeout speed.
125 *
126 * We do this by keeping a floating proportion between BDIs, based
127 * on page writeback completions [end_page_writeback()]. Those
128 * devices that write out pages fastest will get the larger share,
129 * while the slower will get a smaller share.
130 *
131 * We use page writeout completions because we are interested in
132 * getting rid of dirty pages. Having them written out is the
133 * primary goal.
134 *
135 * We introduce a concept of time, a period over which we measure
136 * these events, because demand can/will vary over time. The length
137 * of this period itself is measured in page writeback completions.
138 */
139 struct fprop_global completions;
140 struct timer_list period_timer; /* timer for aging of completions */
141 unsigned long period_time;
142
143 /*
144 * The dirtyable memory and dirty threshold could be suddenly
145 * knocked down by a large amount (eg. on the startup of KVM in a
146 * swapless system). This may throw the system into deep dirty
147 * exceeded state and throttle heavy/light dirtiers alike. To
148 * retain good responsiveness, maintain global_dirty_limit for
149 * tracking slowly down to the knocked down dirty threshold.
150 *
151 * Both fields are protected by ->lock.
152 */
153 unsigned long dirty_limit_tstamp;
154 unsigned long dirty_limit;
155};
156
157/**
158 * wb_domain_size_changed - memory available to a wb_domain has changed
159 * @dom: wb_domain of interest
160 *
161 * This function should be called when the amount of memory available to
162 * @dom has changed. It resets @dom's dirty limit parameters to prevent
163 * the past values which don't match the current configuration from skewing
164 * dirty throttling. Without this, when memory size of a wb_domain is
165 * greatly reduced, the dirty throttling logic may allow too many pages to
166 * be dirtied leading to consecutive unnecessary OOMs and may get stuck in
167 * that situation.
168 */
169static inline void wb_domain_size_changed(struct wb_domain *dom)
170{
171 spin_lock(lock: &dom->lock);
172 dom->dirty_limit_tstamp = jiffies;
173 dom->dirty_limit = 0;
174 spin_unlock(lock: &dom->lock);
175}
176
177/*
178 * fs/fs-writeback.c
179 */
180struct bdi_writeback;
181void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
182void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
183 enum wb_reason reason);
184void try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason);
185void sync_inodes_sb(struct super_block *);
186void wakeup_flusher_threads(enum wb_reason reason);
187void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
188 enum wb_reason reason);
189void inode_wait_for_writeback(struct inode *inode);
190void inode_io_list_del(struct inode *inode);
191
192static inline xa_mark_t wbc_to_tag(struct writeback_control *wbc)
193{
194 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
195 return PAGECACHE_TAG_TOWRITE;
196 return PAGECACHE_TAG_DIRTY;
197}
198
199#ifdef CONFIG_CGROUP_WRITEBACK
200
201#include <linux/cgroup.h>
202#include <linux/bio.h>
203
204void __inode_attach_wb(struct inode *inode, struct folio *folio);
205void wbc_detach_inode(struct writeback_control *wbc);
206void wbc_account_cgroup_owner(struct writeback_control *wbc, struct folio *folio,
207 size_t bytes);
208int cgroup_writeback_by_id(u64 bdi_id, int memcg_id,
209 enum wb_reason reason, struct wb_completion *done);
210void cgroup_writeback_umount(struct super_block *sb);
211bool cleanup_offline_cgwb(struct bdi_writeback *wb);
212
213/**
214 * inode_attach_wb - associate an inode with its wb
215 * @inode: inode of interest
216 * @folio: folio being dirtied (may be NULL)
217 *
218 * If @inode doesn't have its wb, associate it with the wb matching the
219 * memcg of @folio or, if @folio is NULL, %current. May be called w/ or w/o
220 * @inode->i_lock.
221 */
222static inline void inode_attach_wb(struct inode *inode, struct folio *folio)
223{
224 if (!inode->i_wb)
225 __inode_attach_wb(inode, folio);
226}
227
228/**
229 * inode_detach_wb - disassociate an inode from its wb
230 * @inode: inode of interest
231 *
232 * @inode is being freed. Detach from its wb.
233 */
234static inline void inode_detach_wb(struct inode *inode)
235{
236 if (inode->i_wb) {
237 WARN_ON_ONCE(!(inode_state_read_once(inode) & I_CLEAR));
238 wb_put(wb: inode->i_wb);
239 inode->i_wb = NULL;
240 }
241}
242
243void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
244 struct inode *inode);
245
246/**
247 * wbc_init_bio - writeback specific initializtion of bio
248 * @wbc: writeback_control for the writeback in progress
249 * @bio: bio to be initialized
250 *
251 * @bio is a part of the writeback in progress controlled by @wbc. Perform
252 * writeback specific initialization. This is used to apply the cgroup
253 * writeback context. Must be called after the bio has been associated with
254 * a device.
255 */
256static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
257{
258 /*
259 * pageout() path doesn't attach @wbc to the inode being written
260 * out. This is intentional as we don't want the function to block
261 * behind a slow cgroup. Ultimately, we want pageout() to kick off
262 * regular writeback instead of writing things out itself.
263 */
264 if (wbc->wb)
265 bio_associate_blkg_from_css(bio, css: wbc->wb->blkcg_css);
266}
267
268void inode_switch_wbs_work_fn(struct work_struct *work);
269
270#else /* CONFIG_CGROUP_WRITEBACK */
271
272static inline void inode_attach_wb(struct inode *inode, struct folio *folio)
273{
274}
275
276static inline void inode_detach_wb(struct inode *inode)
277{
278}
279
280static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
281 struct inode *inode)
282{
283}
284
285static inline void wbc_detach_inode(struct writeback_control *wbc)
286{
287}
288
289static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
290{
291}
292
293static inline void wbc_account_cgroup_owner(struct writeback_control *wbc,
294 struct folio *folio, size_t bytes)
295{
296}
297
298static inline void cgroup_writeback_umount(struct super_block *sb)
299{
300}
301
302#endif /* CONFIG_CGROUP_WRITEBACK */
303
304/*
305 * mm/page-writeback.c
306 */
307/* consolidated parameters for balance_dirty_pages() and its subroutines */
308struct dirty_throttle_control {
309#ifdef CONFIG_CGROUP_WRITEBACK
310 struct wb_domain *dom;
311 struct dirty_throttle_control *gdtc; /* only set in memcg dtc's */
312#endif
313 struct bdi_writeback *wb;
314 struct fprop_local_percpu *wb_completions;
315
316 unsigned long avail; /* dirtyable */
317 unsigned long dirty; /* file_dirty + write + nfs */
318 unsigned long thresh; /* dirty threshold */
319 unsigned long bg_thresh; /* dirty background threshold */
320 unsigned long limit; /* hard dirty limit */
321
322 unsigned long wb_dirty; /* per-wb counterparts */
323 unsigned long wb_thresh;
324 unsigned long wb_bg_thresh;
325
326 unsigned long pos_ratio;
327 bool freerun;
328 bool dirty_exceeded;
329};
330
331void laptop_io_completion(struct backing_dev_info *info);
332void laptop_sync_completion(void);
333void laptop_mode_timer_fn(struct timer_list *t);
334bool node_dirty_ok(struct pglist_data *pgdat);
335int wb_domain_init(struct wb_domain *dom, gfp_t gfp);
336#ifdef CONFIG_CGROUP_WRITEBACK
337void wb_domain_exit(struct wb_domain *dom);
338#endif
339
340extern struct wb_domain global_wb_domain;
341
342/* These are exported to sysctl. */
343extern unsigned int dirty_writeback_interval;
344extern unsigned int dirty_expire_interval;
345extern int laptop_mode;
346
347void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
348unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
349unsigned long cgwb_calc_thresh(struct bdi_writeback *wb);
350
351void wb_update_bandwidth(struct bdi_writeback *wb);
352
353/* Invoke balance dirty pages in async mode. */
354#define BDP_ASYNC 0x0001
355
356void balance_dirty_pages_ratelimited(struct address_space *mapping);
357int balance_dirty_pages_ratelimited_flags(struct address_space *mapping,
358 unsigned int flags);
359
360bool wb_over_bg_thresh(struct bdi_writeback *wb);
361
362struct folio *writeback_iter(struct address_space *mapping,
363 struct writeback_control *wbc, struct folio *folio, int *error);
364
365int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
366void writeback_set_ratelimit(void);
367void tag_pages_for_writeback(struct address_space *mapping,
368 pgoff_t start, pgoff_t end);
369
370bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio);
371bool folio_redirty_for_writepage(struct writeback_control *, struct folio *);
372bool redirty_page_for_writepage(struct writeback_control *, struct page *);
373
374void sb_mark_inode_writeback(struct inode *inode);
375void sb_clear_inode_writeback(struct inode *inode);
376
377/*
378 * 4MB minimal write chunk size
379 */
380#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_SHIFT - 10))
381
382#endif /* WRITEBACK_H */
383

source code of linux/include/linux/writeback.h