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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 * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
16 * time) for the dirty pages to drop, unless written enough pages.
17 *
18 * The global dirty threshold is normally equal to the global dirty limit,
19 * except when the system suddenly allocates a lot of anonymous memory and
20 * knocks down the global dirty threshold quickly, in which case the global
21 * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
22 */
23#define DIRTY_SCOPE 8
24#define DIRTY_FULL_SCOPE (DIRTY_SCOPE / 2)
25
26/*
27 * 4MB minimal write chunk size
28 */
29#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_CACHE_SHIFT - 10))
30
31struct backing_dev_info;
32
33/*
34 * fs/fs-writeback.c
35 */
36enum writeback_sync_modes {
37 WB_SYNC_NONE, /* Don't wait on anything */
38 WB_SYNC_ALL, /* Wait on every mapping */
39};
40
41/*
42 * why some writeback work was initiated
43 */
44enum wb_reason {
45 WB_REASON_BACKGROUND,
46 WB_REASON_TRY_TO_FREE_PAGES,
47 WB_REASON_SYNC,
48 WB_REASON_PERIODIC,
49 WB_REASON_LAPTOP_TIMER,
50 WB_REASON_FREE_MORE_MEM,
51 WB_REASON_FS_FREE_SPACE,
52 WB_REASON_FORKER_THREAD,
53
54 WB_REASON_MAX,
55};
56extern const char *wb_reason_name[];
57
58/*
59 * A control structure which tells the writeback code what to do. These are
60 * always on the stack, and hence need no locking. They are always initialised
61 * in a manner such that unspecified fields are set to zero.
62 */
63struct writeback_control {
64 enum writeback_sync_modes sync_mode;
65 long nr_to_write; /* Write this many pages, and decrement
66 this for each page written */
67 long pages_skipped; /* Pages which were not written */
68
69 /*
70 * For a_ops->writepages(): is start or end are non-zero then this is
71 * a hint that the filesystem need only write out the pages inside that
72 * byterange. The byte at `end' is included in the writeout request.
73 */
74 loff_t range_start;
75 loff_t range_end;
76
77 unsigned for_kupdate:1; /* A kupdate writeback */
78 unsigned for_background:1; /* A background writeback */
79 unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */
80 unsigned for_reclaim:1; /* Invoked from the page allocator */
81 unsigned range_cyclic:1; /* range_start is cyclic */
82};
83
84/*
85 * fs/fs-writeback.c
86 */
87struct bdi_writeback;
88int inode_wait(void *);
89void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
90void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
91 enum wb_reason reason);
92int writeback_inodes_sb_if_idle(struct super_block *, enum wb_reason reason);
93int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr,
94 enum wb_reason reason);
95void sync_inodes_sb(struct super_block *);
96long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
97 enum wb_reason reason);
98long wb_do_writeback(struct bdi_writeback *wb, int force_wait);
99void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
100
101/* writeback.h requires fs.h; it, too, is not included from here. */
102static inline void wait_on_inode(struct inode *inode)
103{
104 might_sleep();
105 wait_on_bit(&inode->i_state, __I_NEW, inode_wait, TASK_UNINTERRUPTIBLE);
106}
107static inline void inode_sync_wait(struct inode *inode)
108{
109 might_sleep();
110 wait_on_bit(&inode->i_state, __I_SYNC, inode_wait,
111 TASK_UNINTERRUPTIBLE);
112}
113
114
115/*
116 * mm/page-writeback.c
117 */
118#ifdef CONFIG_BLOCK
119void laptop_io_completion(struct backing_dev_info *info);
120void laptop_sync_completion(void);
121void laptop_mode_sync(struct work_struct *work);
122void laptop_mode_timer_fn(unsigned long data);
123#else
124static inline void laptop_sync_completion(void) { }
125#endif
126void throttle_vm_writeout(gfp_t gfp_mask);
127
128extern unsigned long global_dirty_limit;
129
130/* These are exported to sysctl. */
131extern int dirty_background_ratio;
132extern unsigned long dirty_background_bytes;
133extern int vm_dirty_ratio;
134extern unsigned long vm_dirty_bytes;
135extern unsigned int dirty_writeback_interval;
136extern unsigned int dirty_expire_interval;
137extern int vm_highmem_is_dirtyable;
138extern int block_dump;
139extern int laptop_mode;
140
141extern unsigned long determine_dirtyable_memory(void);
142
143extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
144 void __user *buffer, size_t *lenp,
145 loff_t *ppos);
146extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
147 void __user *buffer, size_t *lenp,
148 loff_t *ppos);
149extern int dirty_ratio_handler(struct ctl_table *table, int write,
150 void __user *buffer, size_t *lenp,
151 loff_t *ppos);
152extern int dirty_bytes_handler(struct ctl_table *table, int write,
153 void __user *buffer, size_t *lenp,
154 loff_t *ppos);
155
156struct ctl_table;
157int dirty_writeback_centisecs_handler(struct ctl_table *, int,
158 void __user *, size_t *, loff_t *);
159
160void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
161unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
162 unsigned long dirty);
163
164void __bdi_update_bandwidth(struct backing_dev_info *bdi,
165 unsigned long thresh,
166 unsigned long bg_thresh,
167 unsigned long dirty,
168 unsigned long bdi_thresh,
169 unsigned long bdi_dirty,
170 unsigned long start_time);
171
172void page_writeback_init(void);
173void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
174 unsigned long nr_pages_dirtied);
175
176static inline void
177balance_dirty_pages_ratelimited(struct address_space *mapping)
178{
179 balance_dirty_pages_ratelimited_nr(mapping, 1);
180}
181
182typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
183 void *data);
184
185int generic_writepages(struct address_space *mapping,
186 struct writeback_control *wbc);
187void tag_pages_for_writeback(struct address_space *mapping,
188 pgoff_t start, pgoff_t end);
189int write_cache_pages(struct address_space *mapping,
190 struct writeback_control *wbc, writepage_t writepage,
191 void *data);
192int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
193void set_page_dirty_balance(struct page *page, int page_mkwrite);
194void writeback_set_ratelimit(void);
195void tag_pages_for_writeback(struct address_space *mapping,
196 pgoff_t start, pgoff_t end);
197
198/* pdflush.c */
199extern int nr_pdflush_threads; /* Global so it can be exported to sysctl
200 read-only. */
201
202
203#endif /* WRITEBACK_H */