Linux kernel mirror (for testing)
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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/fs.h>
9
10/*
11 * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
12 *
13 * (thresh - thresh/DIRTY_FULL_SCOPE, thresh)
14 *
15 * The 1/16 region above the global dirty limit will be put to maximum pauses:
16 *
17 * (limit, limit + limit/DIRTY_MAXPAUSE_AREA)
18 *
19 * The 1/16 region above the max-pause region, dirty exceeded bdi's will be put
20 * to loops:
21 *
22 * (limit + limit/DIRTY_MAXPAUSE_AREA, limit + limit/DIRTY_PASSGOOD_AREA)
23 *
24 * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
25 * time) for the dirty pages to drop, unless written enough pages.
26 *
27 * The global dirty threshold is normally equal to the global dirty limit,
28 * except when the system suddenly allocates a lot of anonymous memory and
29 * knocks down the global dirty threshold quickly, in which case the global
30 * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
31 */
32#define DIRTY_SCOPE 8
33#define DIRTY_FULL_SCOPE (DIRTY_SCOPE / 2)
34#define DIRTY_MAXPAUSE_AREA 16
35#define DIRTY_PASSGOOD_AREA 8
36
37/*
38 * 4MB minimal write chunk size
39 */
40#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_CACHE_SHIFT - 10))
41
42struct backing_dev_info;
43
44/*
45 * fs/fs-writeback.c
46 */
47enum writeback_sync_modes {
48 WB_SYNC_NONE, /* Don't wait on anything */
49 WB_SYNC_ALL, /* Wait on every mapping */
50};
51
52/*
53 * A control structure which tells the writeback code what to do. These are
54 * always on the stack, and hence need no locking. They are always initialised
55 * in a manner such that unspecified fields are set to zero.
56 */
57struct writeback_control {
58 enum writeback_sync_modes sync_mode;
59 long nr_to_write; /* Write this many pages, and decrement
60 this for each page written */
61 long pages_skipped; /* Pages which were not written */
62
63 /*
64 * For a_ops->writepages(): is start or end are non-zero then this is
65 * a hint that the filesystem need only write out the pages inside that
66 * byterange. The byte at `end' is included in the writeout request.
67 */
68 loff_t range_start;
69 loff_t range_end;
70
71 unsigned for_kupdate:1; /* A kupdate writeback */
72 unsigned for_background:1; /* A background writeback */
73 unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */
74 unsigned for_reclaim:1; /* Invoked from the page allocator */
75 unsigned range_cyclic:1; /* range_start is cyclic */
76};
77
78/*
79 * fs/fs-writeback.c
80 */
81struct bdi_writeback;
82int inode_wait(void *);
83void writeback_inodes_sb(struct super_block *);
84void writeback_inodes_sb_nr(struct super_block *, unsigned long nr);
85int writeback_inodes_sb_if_idle(struct super_block *);
86int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr);
87void sync_inodes_sb(struct super_block *);
88long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages);
89long wb_do_writeback(struct bdi_writeback *wb, int force_wait);
90void wakeup_flusher_threads(long nr_pages);
91
92/* writeback.h requires fs.h; it, too, is not included from here. */
93static inline void wait_on_inode(struct inode *inode)
94{
95 might_sleep();
96 wait_on_bit(&inode->i_state, __I_NEW, inode_wait, TASK_UNINTERRUPTIBLE);
97}
98static inline void inode_sync_wait(struct inode *inode)
99{
100 might_sleep();
101 wait_on_bit(&inode->i_state, __I_SYNC, inode_wait,
102 TASK_UNINTERRUPTIBLE);
103}
104
105
106/*
107 * mm/page-writeback.c
108 */
109#ifdef CONFIG_BLOCK
110void laptop_io_completion(struct backing_dev_info *info);
111void laptop_sync_completion(void);
112void laptop_mode_sync(struct work_struct *work);
113void laptop_mode_timer_fn(unsigned long data);
114#else
115static inline void laptop_sync_completion(void) { }
116#endif
117void throttle_vm_writeout(gfp_t gfp_mask);
118
119extern unsigned long global_dirty_limit;
120
121/* These are exported to sysctl. */
122extern int dirty_background_ratio;
123extern unsigned long dirty_background_bytes;
124extern int vm_dirty_ratio;
125extern unsigned long vm_dirty_bytes;
126extern unsigned int dirty_writeback_interval;
127extern unsigned int dirty_expire_interval;
128extern int vm_highmem_is_dirtyable;
129extern int block_dump;
130extern int laptop_mode;
131
132extern unsigned long determine_dirtyable_memory(void);
133
134extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
135 void __user *buffer, size_t *lenp,
136 loff_t *ppos);
137extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
138 void __user *buffer, size_t *lenp,
139 loff_t *ppos);
140extern int dirty_ratio_handler(struct ctl_table *table, int write,
141 void __user *buffer, size_t *lenp,
142 loff_t *ppos);
143extern int dirty_bytes_handler(struct ctl_table *table, int write,
144 void __user *buffer, size_t *lenp,
145 loff_t *ppos);
146
147struct ctl_table;
148int dirty_writeback_centisecs_handler(struct ctl_table *, int,
149 void __user *, size_t *, loff_t *);
150
151void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
152unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
153 unsigned long dirty);
154
155void __bdi_update_bandwidth(struct backing_dev_info *bdi,
156 unsigned long thresh,
157 unsigned long dirty,
158 unsigned long bdi_thresh,
159 unsigned long bdi_dirty,
160 unsigned long start_time);
161
162void page_writeback_init(void);
163void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
164 unsigned long nr_pages_dirtied);
165
166static inline void
167balance_dirty_pages_ratelimited(struct address_space *mapping)
168{
169 balance_dirty_pages_ratelimited_nr(mapping, 1);
170}
171
172typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
173 void *data);
174
175int generic_writepages(struct address_space *mapping,
176 struct writeback_control *wbc);
177void tag_pages_for_writeback(struct address_space *mapping,
178 pgoff_t start, pgoff_t end);
179int write_cache_pages(struct address_space *mapping,
180 struct writeback_control *wbc, writepage_t writepage,
181 void *data);
182int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
183void set_page_dirty_balance(struct page *page, int page_mkwrite);
184void writeback_set_ratelimit(void);
185void tag_pages_for_writeback(struct address_space *mapping,
186 pgoff_t start, pgoff_t end);
187
188/* pdflush.c */
189extern int nr_pdflush_threads; /* Global so it can be exported to sysctl
190 read-only. */
191
192
193#endif /* WRITEBACK_H */