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
11 DECLARE_PER_CPU(int, dirty_throttle_leaks);
12
13 /*
14 * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
15 *
16 * (thresh - thresh/DIRTY_FULL_SCOPE, thresh)
17 *
18 * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
19 * time) for the dirty pages to drop, unless written enough pages.
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 #define DIRTY_FULL_SCOPE (DIRTY_SCOPE / 2)
28
29 struct backing_dev_info;
30
31 /*
32 * fs/fs-writeback.c
33 */
34 enum writeback_sync_modes {
35 WB_SYNC_NONE, /* Don't wait on anything */
36 WB_SYNC_ALL, /* Wait on every mapping */
37 };
38
39 /*
40 * why some writeback work was initiated
41 */
42 enum wb_reason {
43 WB_REASON_BACKGROUND,
44 WB_REASON_TRY_TO_FREE_PAGES,
45 WB_REASON_SYNC,
46 WB_REASON_PERIODIC,
47 WB_REASON_LAPTOP_TIMER,
48 WB_REASON_FREE_MORE_MEM,
49 WB_REASON_FS_FREE_SPACE,
50 /*
51 * There is no bdi forker thread any more and works are done
52 * by emergency worker, however, this is TPs userland visible
53 * and we'll be exposing exactly the same information,
54 * so it has a mismatch name.
55 */
56 WB_REASON_FORKER_THREAD,
57
58 WB_REASON_MAX,
59 };
60
61 /*
62 * A control structure which tells the writeback code what to do. These are
63 * always on the stack, and hence need no locking. They are always initialised
64 * in a manner such that unspecified fields are set to zero.
65 */
66 struct writeback_control {
67 long nr_to_write; /* Write this many pages, and decrement
68 this for each page written */
69 long pages_skipped; /* Pages which were not written */
70
71 /*
72 * For a_ops->writepages(): if start or end are non-zero then this is
73 * a hint that the filesystem need only write out the pages inside that
74 * byterange. The byte at `end' is included in the writeout request.
75 */
76 loff_t range_start;
77 loff_t range_end;
78
79 enum writeback_sync_modes sync_mode;
80
81 unsigned for_kupdate:1; /* A kupdate writeback */
82 unsigned for_background:1; /* A background writeback */
83 unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */
84 unsigned for_reclaim:1; /* Invoked from the page allocator */
85 unsigned range_cyclic:1; /* range_start is cyclic */
86 unsigned for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
87 };
88
89 /*
90 * fs/fs-writeback.c
91 */
92 struct bdi_writeback;
93 void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
94 void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
95 enum wb_reason reason);
96 int try_to_writeback_inodes_sb(struct super_block *, enum wb_reason reason);
97 int try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
98 enum wb_reason reason);
99 void sync_inodes_sb(struct super_block *);
100 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
101 void inode_wait_for_writeback(struct inode *inode);
102
103 /* writeback.h requires fs.h; it, too, is not included from here. */
wait_on_inode(struct inode * inode)104 static inline void wait_on_inode(struct inode *inode)
105 {
106 might_sleep();
107 wait_on_bit(&inode->i_state, __I_NEW, TASK_UNINTERRUPTIBLE);
108 }
109
110 /*
111 * mm/page-writeback.c
112 */
113 #ifdef CONFIG_BLOCK
114 void laptop_io_completion(struct backing_dev_info *info);
115 void laptop_sync_completion(void);
116 void laptop_mode_sync(struct work_struct *work);
117 void laptop_mode_timer_fn(unsigned long data);
118 #else
laptop_sync_completion(void)119 static inline void laptop_sync_completion(void) { }
120 #endif
121 void throttle_vm_writeout(gfp_t gfp_mask);
122 bool zone_dirty_ok(struct zone *zone);
123
124 extern unsigned long global_dirty_limit;
125
126 /* These are exported to sysctl. */
127 extern int dirty_background_ratio;
128 extern unsigned long dirty_background_bytes;
129 extern int vm_dirty_ratio;
130 extern unsigned long vm_dirty_bytes;
131 extern unsigned int dirty_writeback_interval;
132 extern unsigned int dirty_expire_interval;
133 extern int vm_highmem_is_dirtyable;
134 extern int block_dump;
135 extern int laptop_mode;
136
137 extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
138 void __user *buffer, size_t *lenp,
139 loff_t *ppos);
140 extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
141 void __user *buffer, size_t *lenp,
142 loff_t *ppos);
143 extern int dirty_ratio_handler(struct ctl_table *table, int write,
144 void __user *buffer, size_t *lenp,
145 loff_t *ppos);
146 extern int dirty_bytes_handler(struct ctl_table *table, int write,
147 void __user *buffer, size_t *lenp,
148 loff_t *ppos);
149
150 struct ctl_table;
151 int dirty_writeback_centisecs_handler(struct ctl_table *, int,
152 void __user *, size_t *, loff_t *);
153
154 void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
155 unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
156 unsigned long dirty);
157
158 void __bdi_update_bandwidth(struct backing_dev_info *bdi,
159 unsigned long thresh,
160 unsigned long bg_thresh,
161 unsigned long dirty,
162 unsigned long bdi_thresh,
163 unsigned long bdi_dirty,
164 unsigned long start_time);
165
166 void page_writeback_init(void);
167 void balance_dirty_pages_ratelimited(struct address_space *mapping);
168
169 typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
170 void *data);
171
172 int generic_writepages(struct address_space *mapping,
173 struct writeback_control *wbc);
174 void tag_pages_for_writeback(struct address_space *mapping,
175 pgoff_t start, pgoff_t end);
176 int write_cache_pages(struct address_space *mapping,
177 struct writeback_control *wbc, writepage_t writepage,
178 void *data);
179 int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
180 void writeback_set_ratelimit(void);
181 void tag_pages_for_writeback(struct address_space *mapping,
182 pgoff_t start, pgoff_t end);
183
184 void account_page_redirty(struct page *page);
185
186 #endif /* WRITEBACK_H */
187