1 /* SPDX-License-Identifier: GPL-2.0 */
3 * include/linux/writeback.h
8 #include <linux/sched.h>
9 #include <linux/workqueue.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>
18 DECLARE_PER_CPU(int, dirty_throttle_leaks
);
21 * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
23 * (thresh - thresh/DIRTY_FULL_SCOPE, thresh)
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.
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.
34 #define DIRTY_FULL_SCOPE (DIRTY_SCOPE / 2)
36 struct backing_dev_info
;
41 enum writeback_sync_modes
{
42 WB_SYNC_NONE
, /* Don't wait on anything */
43 WB_SYNC_ALL
, /* Wait on every mapping */
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.
51 struct 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 */
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.
64 enum writeback_sync_modes sync_mode
;
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 */
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.
79 unsigned no_cgroup_owner
:1;
81 unsigned punt_to_cgroup
:1; /* cgrp punting, see __REQ_CGROUP_PUNT */
83 #ifdef CONFIG_CGROUP_WRITEBACK
84 struct bdi_writeback
*wb
; /* wb this writeback is issued under */
85 struct inode
*inode
; /* inode being written out */
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 */
97 static inline int wbc_to_write_flags(struct writeback_control
*wbc
)
101 if (wbc
->punt_to_cgroup
)
102 flags
= REQ_CGROUP_PUNT
;
104 if (wbc
->sync_mode
== WB_SYNC_ALL
)
106 else if (wbc
->for_kupdate
|| wbc
->for_background
)
107 flags
|= REQ_BACKGROUND
;
112 static inline struct cgroup_subsys_state
*
113 wbc_blkcg_css(struct writeback_control
*wbc
)
115 #ifdef CONFIG_CGROUP_WRITEBACK
117 return wbc
->wb
->blkcg_css
;
119 return blkcg_root_css
;
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.
133 * Scale the writeback cache size proportional to the relative
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.
141 * We use page writeout completions because we are interested in
142 * getting rid of dirty pages. Having them written out is the
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.
149 struct fprop_global completions
;
150 struct timer_list period_timer
; /* timer for aging of completions */
151 unsigned long period_time
;
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.
161 * Both fields are protected by ->lock.
163 unsigned long dirty_limit_tstamp
;
164 unsigned long dirty_limit
;
168 * wb_domain_size_changed - memory available to a wb_domain has changed
169 * @dom: wb_domain of interest
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
179 static inline void wb_domain_size_changed(struct wb_domain
*dom
)
181 spin_lock(&dom
->lock
);
182 dom
->dirty_limit_tstamp
= jiffies
;
183 dom
->dirty_limit
= 0;
184 spin_unlock(&dom
->lock
);
190 struct bdi_writeback
;
191 void writeback_inodes_sb(struct super_block
*, enum wb_reason reason
);
192 void writeback_inodes_sb_nr(struct super_block
*, unsigned long nr
,
193 enum wb_reason reason
);
194 void try_to_writeback_inodes_sb(struct super_block
*sb
, enum wb_reason reason
);
195 void sync_inodes_sb(struct super_block
*);
196 void wakeup_flusher_threads(enum wb_reason reason
);
197 void wakeup_flusher_threads_bdi(struct backing_dev_info
*bdi
,
198 enum wb_reason reason
);
199 void inode_wait_for_writeback(struct inode
*inode
);
201 /* writeback.h requires fs.h; it, too, is not included from here. */
202 static inline void wait_on_inode(struct inode
*inode
)
205 wait_on_bit(&inode
->i_state
, __I_NEW
, TASK_UNINTERRUPTIBLE
);
208 #ifdef CONFIG_CGROUP_WRITEBACK
210 #include <linux/cgroup.h>
211 #include <linux/bio.h>
213 void __inode_attach_wb(struct inode
*inode
, struct page
*page
);
214 void wbc_attach_and_unlock_inode(struct writeback_control
*wbc
,
216 __releases(&inode
->i_lock
);
217 void wbc_detach_inode(struct writeback_control
*wbc
);
218 void wbc_account_cgroup_owner(struct writeback_control
*wbc
, struct page
*page
,
220 int cgroup_writeback_by_id(u64 bdi_id
, int memcg_id
, unsigned long nr_pages
,
221 enum wb_reason reason
, struct wb_completion
*done
);
222 void cgroup_writeback_umount(void);
225 * inode_attach_wb - associate an inode with its wb
226 * @inode: inode of interest
227 * @page: page being dirtied (may be NULL)
229 * If @inode doesn't have its wb, associate it with the wb matching the
230 * memcg of @page or, if @page is NULL, %current. May be called w/ or w/o
233 static inline void inode_attach_wb(struct inode
*inode
, struct page
*page
)
236 __inode_attach_wb(inode
, page
);
240 * inode_detach_wb - disassociate an inode from its wb
241 * @inode: inode of interest
243 * @inode is being freed. Detach from its wb.
245 static inline void inode_detach_wb(struct inode
*inode
)
248 WARN_ON_ONCE(!(inode
->i_state
& I_CLEAR
));
255 * wbc_attach_fdatawrite_inode - associate wbc and inode for fdatawrite
256 * @wbc: writeback_control of interest
257 * @inode: target inode
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.
263 static inline void wbc_attach_fdatawrite_inode(struct writeback_control
*wbc
,
266 spin_lock(&inode
->i_lock
);
267 inode_attach_wb(inode
, NULL
);
268 wbc_attach_and_unlock_inode(wbc
, inode
);
272 * wbc_init_bio - writeback specific initializtion of bio
273 * @wbc: writeback_control for the writeback in progress
274 * @bio: bio to be initialized
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
281 static inline void wbc_init_bio(struct writeback_control
*wbc
, struct bio
*bio
)
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.
290 bio_associate_blkg_from_css(bio
, wbc
->wb
->blkcg_css
);
293 #else /* CONFIG_CGROUP_WRITEBACK */
295 static inline void inode_attach_wb(struct inode
*inode
, struct page
*page
)
299 static inline void inode_detach_wb(struct inode
*inode
)
303 static inline void wbc_attach_and_unlock_inode(struct writeback_control
*wbc
,
305 __releases(&inode
->i_lock
)
307 spin_unlock(&inode
->i_lock
);
310 static inline void wbc_attach_fdatawrite_inode(struct writeback_control
*wbc
,
315 static inline void wbc_detach_inode(struct writeback_control
*wbc
)
319 static inline void wbc_init_bio(struct writeback_control
*wbc
, struct bio
*bio
)
323 static inline void wbc_account_cgroup_owner(struct writeback_control
*wbc
,
324 struct page
*page
, size_t bytes
)
328 static inline void cgroup_writeback_umount(void)
332 #endif /* CONFIG_CGROUP_WRITEBACK */
335 * mm/page-writeback.c
338 void laptop_io_completion(struct backing_dev_info
*info
);
339 void laptop_sync_completion(void);
340 void laptop_mode_sync(struct work_struct
*work
);
341 void laptop_mode_timer_fn(struct timer_list
*t
);
343 static inline void laptop_sync_completion(void) { }
345 bool node_dirty_ok(struct pglist_data
*pgdat
);
346 int wb_domain_init(struct wb_domain
*dom
, gfp_t gfp
);
347 #ifdef CONFIG_CGROUP_WRITEBACK
348 void wb_domain_exit(struct wb_domain
*dom
);
351 extern struct wb_domain global_wb_domain
;
353 /* These are exported to sysctl. */
354 extern int dirty_background_ratio
;
355 extern unsigned long dirty_background_bytes
;
356 extern int vm_dirty_ratio
;
357 extern unsigned long vm_dirty_bytes
;
358 extern unsigned int dirty_writeback_interval
;
359 extern unsigned int dirty_expire_interval
;
360 extern unsigned int dirtytime_expire_interval
;
361 extern int vm_highmem_is_dirtyable
;
362 extern int block_dump
;
363 extern int laptop_mode
;
365 extern int dirty_background_ratio_handler(struct ctl_table
*table
, int write
,
366 void __user
*buffer
, size_t *lenp
,
368 extern int dirty_background_bytes_handler(struct ctl_table
*table
, int write
,
369 void __user
*buffer
, size_t *lenp
,
371 extern int dirty_ratio_handler(struct ctl_table
*table
, int write
,
372 void __user
*buffer
, size_t *lenp
,
374 extern int dirty_bytes_handler(struct ctl_table
*table
, int write
,
375 void __user
*buffer
, size_t *lenp
,
377 int dirtytime_interval_handler(struct ctl_table
*table
, int write
,
378 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
);
381 int dirty_writeback_centisecs_handler(struct ctl_table
*, int,
382 void __user
*, size_t *, loff_t
*);
384 void global_dirty_limits(unsigned long *pbackground
, unsigned long *pdirty
);
385 unsigned long wb_calc_thresh(struct bdi_writeback
*wb
, unsigned long thresh
);
387 void wb_update_bandwidth(struct bdi_writeback
*wb
, unsigned long start_time
);
388 void balance_dirty_pages_ratelimited(struct address_space
*mapping
);
389 bool wb_over_bg_thresh(struct bdi_writeback
*wb
);
391 typedef int (*writepage_t
)(struct page
*page
, struct writeback_control
*wbc
,
394 int generic_writepages(struct address_space
*mapping
,
395 struct writeback_control
*wbc
);
396 void tag_pages_for_writeback(struct address_space
*mapping
,
397 pgoff_t start
, pgoff_t end
);
398 int write_cache_pages(struct address_space
*mapping
,
399 struct writeback_control
*wbc
, writepage_t writepage
,
401 int do_writepages(struct address_space
*mapping
, struct writeback_control
*wbc
);
402 void writeback_set_ratelimit(void);
403 void tag_pages_for_writeback(struct address_space
*mapping
,
404 pgoff_t start
, pgoff_t end
);
406 void account_page_redirty(struct page
*page
);
408 void sb_mark_inode_writeback(struct inode
*inode
);
409 void sb_clear_inode_writeback(struct inode
*inode
);
411 #endif /* WRITEBACK_H */