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TOMOYO Linux Cross Reference
Linux/include/linux/writeback.h

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  1 /*
  2  * include/linux/writeback.h
  3  */
  4 #ifndef WRITEBACK_H
  5 #define WRITEBACK_H
  6 
  7 #include <linux/sched.h>
  8 #include <linux/workqueue.h>
  9 #include <linux/fs.h>
 10 #include <linux/flex_proportions.h>
 11 #include <linux/backing-dev-defs.h>
 12 #include <linux/blk_types.h>
 13 
 14 struct bio;
 15 
 16 DECLARE_PER_CPU(int, dirty_throttle_leaks);
 17 
 18 /*
 19  * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
 20  *
 21  *      (thresh - thresh/DIRTY_FULL_SCOPE, thresh)
 22  *
 23  * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
 24  * time) for the dirty pages to drop, unless written enough pages.
 25  *
 26  * The global dirty threshold is normally equal to the global dirty limit,
 27  * except when the system suddenly allocates a lot of anonymous memory and
 28  * knocks down the global dirty threshold quickly, in which case the global
 29  * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
 30  */
 31 #define DIRTY_SCOPE             8
 32 #define DIRTY_FULL_SCOPE        (DIRTY_SCOPE / 2)
 33 
 34 struct backing_dev_info;
 35 
 36 /*
 37  * fs/fs-writeback.c
 38  */
 39 enum writeback_sync_modes {
 40         WB_SYNC_NONE,   /* Don't wait on anything */
 41         WB_SYNC_ALL,    /* Wait on every mapping */
 42 };
 43 
 44 /*
 45  * why some writeback work was initiated
 46  */
 47 enum wb_reason {
 48         WB_REASON_BACKGROUND,
 49         WB_REASON_VMSCAN,
 50         WB_REASON_SYNC,
 51         WB_REASON_PERIODIC,
 52         WB_REASON_LAPTOP_TIMER,
 53         WB_REASON_FREE_MORE_MEM,
 54         WB_REASON_FS_FREE_SPACE,
 55         /*
 56          * There is no bdi forker thread any more and works are done
 57          * by emergency worker, however, this is TPs userland visible
 58          * and we'll be exposing exactly the same information,
 59          * so it has a mismatch name.
 60          */
 61         WB_REASON_FORKER_THREAD,
 62 
 63         WB_REASON_MAX,
 64 };
 65 
 66 /*
 67  * A control structure which tells the writeback code what to do.  These are
 68  * always on the stack, and hence need no locking.  They are always initialised
 69  * in a manner such that unspecified fields are set to zero.
 70  */
 71 struct writeback_control {
 72         long nr_to_write;               /* Write this many pages, and decrement
 73                                            this for each page written */
 74         long pages_skipped;             /* Pages which were not written */
 75 
 76         /*
 77          * For a_ops->writepages(): if start or end are non-zero then this is
 78          * a hint that the filesystem need only write out the pages inside that
 79          * byterange.  The byte at `end' is included in the writeout request.
 80          */
 81         loff_t range_start;
 82         loff_t range_end;
 83 
 84         enum writeback_sync_modes sync_mode;
 85 
 86         unsigned for_kupdate:1;         /* A kupdate writeback */
 87         unsigned for_background:1;      /* A background writeback */
 88         unsigned tagged_writepages:1;   /* tag-and-write to avoid livelock */
 89         unsigned for_reclaim:1;         /* Invoked from the page allocator */
 90         unsigned range_cyclic:1;        /* range_start is cyclic */
 91         unsigned for_sync:1;            /* sync(2) WB_SYNC_ALL writeback */
 92 #ifdef CONFIG_CGROUP_WRITEBACK
 93         struct bdi_writeback *wb;       /* wb this writeback is issued under */
 94         struct inode *inode;            /* inode being written out */
 95 
 96         /* foreign inode detection, see wbc_detach_inode() */
 97         int wb_id;                      /* current wb id */
 98         int wb_lcand_id;                /* last foreign candidate wb id */
 99         int wb_tcand_id;                /* this foreign candidate wb id */
100         size_t wb_bytes;                /* bytes written by current wb */
101         size_t wb_lcand_bytes;          /* bytes written by last candidate */
102         size_t wb_tcand_bytes;          /* bytes written by this candidate */
103 #endif
104 };
105 
106 static inline int wbc_to_write_flags(struct writeback_control *wbc)
107 {
108         if (wbc->sync_mode == WB_SYNC_ALL)
109                 return REQ_SYNC;
110         else if (wbc->for_kupdate || wbc->for_background)
111                 return REQ_BACKGROUND;
112 
113         return 0;
114 }
115 
116 /*
117  * A wb_domain represents a domain that wb's (bdi_writeback's) belong to
118  * and are measured against each other in.  There always is one global
119  * domain, global_wb_domain, that every wb in the system is a member of.
120  * This allows measuring the relative bandwidth of each wb to distribute
121  * dirtyable memory accordingly.
122  */
123 struct wb_domain {
124         spinlock_t lock;
125 
126         /*
127          * Scale the writeback cache size proportional to the relative
128          * writeout speed.
129          *
130          * We do this by keeping a floating proportion between BDIs, based
131          * on page writeback completions [end_page_writeback()]. Those
132          * devices that write out pages fastest will get the larger share,
133          * while the slower will get a smaller share.
134          *
135          * We use page writeout completions because we are interested in
136          * getting rid of dirty pages. Having them written out is the
137          * primary goal.
138          *
139          * We introduce a concept of time, a period over which we measure
140          * these events, because demand can/will vary over time. The length
141          * of this period itself is measured in page writeback completions.
142          */
143         struct fprop_global completions;
144         struct timer_list period_timer; /* timer for aging of completions */
145         unsigned long period_time;
146 
147         /*
148          * The dirtyable memory and dirty threshold could be suddenly
149          * knocked down by a large amount (eg. on the startup of KVM in a
150          * swapless system). This may throw the system into deep dirty
151          * exceeded state and throttle heavy/light dirtiers alike. To
152          * retain good responsiveness, maintain global_dirty_limit for
153          * tracking slowly down to the knocked down dirty threshold.
154          *
155          * Both fields are protected by ->lock.
156          */
157         unsigned long dirty_limit_tstamp;
158         unsigned long dirty_limit;
159 };
160 
161 /**
162  * wb_domain_size_changed - memory available to a wb_domain has changed
163  * @dom: wb_domain of interest
164  *
165  * This function should be called when the amount of memory available to
166  * @dom has changed.  It resets @dom's dirty limit parameters to prevent
167  * the past values which don't match the current configuration from skewing
168  * dirty throttling.  Without this, when memory size of a wb_domain is
169  * greatly reduced, the dirty throttling logic may allow too many pages to
170  * be dirtied leading to consecutive unnecessary OOMs and may get stuck in
171  * that situation.
172  */
173 static inline void wb_domain_size_changed(struct wb_domain *dom)
174 {
175         spin_lock(&dom->lock);
176         dom->dirty_limit_tstamp = jiffies;
177         dom->dirty_limit = 0;
178         spin_unlock(&dom->lock);
179 }
180 
181 /*
182  * fs/fs-writeback.c
183  */     
184 struct bdi_writeback;
185 void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
186 void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
187                                                         enum wb_reason reason);
188 bool try_to_writeback_inodes_sb(struct super_block *, enum wb_reason reason);
189 bool try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
190                                    enum wb_reason reason);
191 void sync_inodes_sb(struct super_block *);
192 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
193 void inode_wait_for_writeback(struct inode *inode);
194 
195 /* writeback.h requires fs.h; it, too, is not included from here. */
196 static inline void wait_on_inode(struct inode *inode)
197 {
198         might_sleep();
199         wait_on_bit(&inode->i_state, __I_NEW, TASK_UNINTERRUPTIBLE);
200 }
201 
202 #ifdef CONFIG_CGROUP_WRITEBACK
203 
204 #include <linux/cgroup.h>
205 #include <linux/bio.h>
206 
207 void __inode_attach_wb(struct inode *inode, struct page *page);
208 void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
209                                  struct inode *inode)
210         __releases(&inode->i_lock);
211 void wbc_detach_inode(struct writeback_control *wbc);
212 void wbc_account_io(struct writeback_control *wbc, struct page *page,
213                     size_t bytes);
214 void cgroup_writeback_umount(void);
215 
216 /**
217  * inode_attach_wb - associate an inode with its wb
218  * @inode: inode of interest
219  * @page: page being dirtied (may be NULL)
220  *
221  * If @inode doesn't have its wb, associate it with the wb matching the
222  * memcg of @page or, if @page is NULL, %current.  May be called w/ or w/o
223  * @inode->i_lock.
224  */
225 static inline void inode_attach_wb(struct inode *inode, struct page *page)
226 {
227         if (!inode->i_wb)
228                 __inode_attach_wb(inode, page);
229 }
230 
231 /**
232  * inode_detach_wb - disassociate an inode from its wb
233  * @inode: inode of interest
234  *
235  * @inode is being freed.  Detach from its wb.
236  */
237 static inline void inode_detach_wb(struct inode *inode)
238 {
239         if (inode->i_wb) {
240                 wb_put(inode->i_wb);
241                 inode->i_wb = NULL;
242         }
243 }
244 
245 /**
246  * wbc_attach_fdatawrite_inode - associate wbc and inode for fdatawrite
247  * @wbc: writeback_control of interest
248  * @inode: target inode
249  *
250  * This function is to be used by __filemap_fdatawrite_range(), which is an
251  * alternative entry point into writeback code, and first ensures @inode is
252  * associated with a bdi_writeback and attaches it to @wbc.
253  */
254 static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
255                                                struct inode *inode)
256 {
257         spin_lock(&inode->i_lock);
258         inode_attach_wb(inode, NULL);
259         wbc_attach_and_unlock_inode(wbc, inode);
260 }
261 
262 /**
263  * wbc_init_bio - writeback specific initializtion of bio
264  * @wbc: writeback_control for the writeback in progress
265  * @bio: bio to be initialized
266  *
267  * @bio is a part of the writeback in progress controlled by @wbc.  Perform
268  * writeback specific initialization.  This is used to apply the cgroup
269  * writeback context.
270  */
271 static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
272 {
273         /*
274          * pageout() path doesn't attach @wbc to the inode being written
275          * out.  This is intentional as we don't want the function to block
276          * behind a slow cgroup.  Ultimately, we want pageout() to kick off
277          * regular writeback instead of writing things out itself.
278          */
279         if (wbc->wb)
280                 bio_associate_blkcg(bio, wbc->wb->blkcg_css);
281 }
282 
283 #else   /* CONFIG_CGROUP_WRITEBACK */
284 
285 static inline void inode_attach_wb(struct inode *inode, struct page *page)
286 {
287 }
288 
289 static inline void inode_detach_wb(struct inode *inode)
290 {
291 }
292 
293 static inline void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
294                                                struct inode *inode)
295         __releases(&inode->i_lock)
296 {
297         spin_unlock(&inode->i_lock);
298 }
299 
300 static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
301                                                struct inode *inode)
302 {
303 }
304 
305 static inline void wbc_detach_inode(struct writeback_control *wbc)
306 {
307 }
308 
309 static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
310 {
311 }
312 
313 static inline void wbc_account_io(struct writeback_control *wbc,
314                                   struct page *page, size_t bytes)
315 {
316 }
317 
318 static inline void cgroup_writeback_umount(void)
319 {
320 }
321 
322 #endif  /* CONFIG_CGROUP_WRITEBACK */
323 
324 /*
325  * mm/page-writeback.c
326  */
327 #ifdef CONFIG_BLOCK
328 void laptop_io_completion(struct backing_dev_info *info);
329 void laptop_sync_completion(void);
330 void laptop_mode_sync(struct work_struct *work);
331 void laptop_mode_timer_fn(unsigned long data);
332 #else
333 static inline void laptop_sync_completion(void) { }
334 #endif
335 bool node_dirty_ok(struct pglist_data *pgdat);
336 int wb_domain_init(struct wb_domain *dom, gfp_t gfp);
337 #ifdef CONFIG_CGROUP_WRITEBACK
338 void wb_domain_exit(struct wb_domain *dom);
339 #endif
340 
341 extern struct wb_domain global_wb_domain;
342 
343 /* These are exported to sysctl. */
344 extern int dirty_background_ratio;
345 extern unsigned long dirty_background_bytes;
346 extern int vm_dirty_ratio;
347 extern unsigned long vm_dirty_bytes;
348 extern unsigned int dirty_writeback_interval;
349 extern unsigned int dirty_expire_interval;
350 extern unsigned int dirtytime_expire_interval;
351 extern int vm_highmem_is_dirtyable;
352 extern int block_dump;
353 extern int laptop_mode;
354 
355 extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
356                 void __user *buffer, size_t *lenp,
357                 loff_t *ppos);
358 extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
359                 void __user *buffer, size_t *lenp,
360                 loff_t *ppos);
361 extern int dirty_ratio_handler(struct ctl_table *table, int write,
362                 void __user *buffer, size_t *lenp,
363                 loff_t *ppos);
364 extern int dirty_bytes_handler(struct ctl_table *table, int write,
365                 void __user *buffer, size_t *lenp,
366                 loff_t *ppos);
367 int dirtytime_interval_handler(struct ctl_table *table, int write,
368                                void __user *buffer, size_t *lenp, loff_t *ppos);
369 
370 struct ctl_table;
371 int dirty_writeback_centisecs_handler(struct ctl_table *, int,
372                                       void __user *, size_t *, loff_t *);
373 
374 void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
375 unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
376 
377 void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time);
378 void balance_dirty_pages_ratelimited(struct address_space *mapping);
379 bool wb_over_bg_thresh(struct bdi_writeback *wb);
380 
381 typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
382                                 void *data);
383 
384 int generic_writepages(struct address_space *mapping,
385                        struct writeback_control *wbc);
386 void tag_pages_for_writeback(struct address_space *mapping,
387                              pgoff_t start, pgoff_t end);
388 int write_cache_pages(struct address_space *mapping,
389                       struct writeback_control *wbc, writepage_t writepage,
390                       void *data);
391 int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
392 void writeback_set_ratelimit(void);
393 void tag_pages_for_writeback(struct address_space *mapping,
394                              pgoff_t start, pgoff_t end);
395 
396 void account_page_redirty(struct page *page);
397 
398 void sb_mark_inode_writeback(struct inode *inode);
399 void sb_clear_inode_writeback(struct inode *inode);
400 
401 #endif          /* WRITEBACK_H */
402 

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