995b8bf630aca90e6c29f0f0d919e95c51586c10
[linux-2.6.git] / include / linux / writeback.h
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 DECLARE_PER_CPU(int, dirty_throttle_leaks);
11
12 /*
13  * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
14  *
15  *      (thresh - thresh/DIRTY_FULL_SCOPE, thresh)
16  *
17  * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
18  * time) for the dirty pages to drop, unless written enough pages.
19  *
20  * The global dirty threshold is normally equal to the global dirty limit,
21  * except when the system suddenly allocates a lot of anonymous memory and
22  * knocks down the global dirty threshold quickly, in which case the global
23  * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
24  */
25 #define DIRTY_SCOPE             8
26 #define DIRTY_FULL_SCOPE        (DIRTY_SCOPE / 2)
27
28 struct backing_dev_info;
29
30 /*
31  * fs/fs-writeback.c
32  */
33 enum writeback_sync_modes {
34         WB_SYNC_NONE,   /* Don't wait on anything */
35         WB_SYNC_ALL,    /* Wait on every mapping */
36 };
37
38 /*
39  * why some writeback work was initiated
40  */
41 enum wb_reason {
42         WB_REASON_BACKGROUND,
43         WB_REASON_TRY_TO_FREE_PAGES,
44         WB_REASON_SYNC,
45         WB_REASON_PERIODIC,
46         WB_REASON_LAPTOP_TIMER,
47         WB_REASON_FREE_MORE_MEM,
48         WB_REASON_FS_FREE_SPACE,
49         WB_REASON_FORKER_THREAD,
50
51         WB_REASON_MAX,
52 };
53 extern const char *wb_reason_name[];
54
55 /*
56  * A control structure which tells the writeback code what to do.  These are
57  * always on the stack, and hence need no locking.  They are always initialised
58  * in a manner such that unspecified fields are set to zero.
59  */
60 struct writeback_control {
61         enum writeback_sync_modes sync_mode;
62         long nr_to_write;               /* Write this many pages, and decrement
63                                            this for each page written */
64         long pages_skipped;             /* Pages which were not written */
65
66         /*
67          * For a_ops->writepages(): is start or end are non-zero then this is
68          * a hint that the filesystem need only write out the pages inside that
69          * byterange.  The byte at `end' is included in the writeout request.
70          */
71         loff_t range_start;
72         loff_t range_end;
73
74         unsigned for_kupdate:1;         /* A kupdate writeback */
75         unsigned for_background:1;      /* A background writeback */
76         unsigned tagged_writepages:1;   /* tag-and-write to avoid livelock */
77         unsigned for_reclaim:1;         /* Invoked from the page allocator */
78         unsigned range_cyclic:1;        /* range_start is cyclic */
79 };
80
81 /*
82  * fs/fs-writeback.c
83  */     
84 struct bdi_writeback;
85 int inode_wait(void *);
86 void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
87 void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
88                                                         enum wb_reason reason);
89 int writeback_inodes_sb_if_idle(struct super_block *, enum wb_reason reason);
90 int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr,
91                                                         enum wb_reason reason);
92 void sync_inodes_sb(struct super_block *);
93 long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
94                                 enum wb_reason reason);
95 long wb_do_writeback(struct bdi_writeback *wb, int force_wait);
96 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
97
98 /* writeback.h requires fs.h; it, too, is not included from here. */
99 static inline void wait_on_inode(struct inode *inode)
100 {
101         might_sleep();
102         wait_on_bit(&inode->i_state, __I_NEW, inode_wait, TASK_UNINTERRUPTIBLE);
103 }
104 static inline void inode_sync_wait(struct inode *inode)
105 {
106         might_sleep();
107         wait_on_bit(&inode->i_state, __I_SYNC, inode_wait,
108                                                         TASK_UNINTERRUPTIBLE);
109 }
110
111
112 /*
113  * mm/page-writeback.c
114  */
115 #ifdef CONFIG_BLOCK
116 void laptop_io_completion(struct backing_dev_info *info);
117 void laptop_sync_completion(void);
118 void laptop_mode_sync(struct work_struct *work);
119 void laptop_mode_timer_fn(unsigned long data);
120 #else
121 static inline void laptop_sync_completion(void) { }
122 #endif
123 void throttle_vm_writeout(gfp_t gfp_mask);
124 bool zone_dirty_ok(struct zone *zone);
125
126 extern unsigned long global_dirty_limit;
127
128 /* These are exported to sysctl. */
129 extern int dirty_background_ratio;
130 extern unsigned long dirty_background_bytes;
131 extern int vm_dirty_ratio;
132 extern unsigned long vm_dirty_bytes;
133 extern unsigned int dirty_writeback_interval;
134 extern unsigned int dirty_expire_interval;
135 extern int vm_highmem_is_dirtyable;
136 extern int block_dump;
137 extern int laptop_mode;
138
139 extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
140                 void __user *buffer, size_t *lenp,
141                 loff_t *ppos);
142 extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
143                 void __user *buffer, size_t *lenp,
144                 loff_t *ppos);
145 extern int dirty_ratio_handler(struct ctl_table *table, int write,
146                 void __user *buffer, size_t *lenp,
147                 loff_t *ppos);
148 extern int dirty_bytes_handler(struct ctl_table *table, int write,
149                 void __user *buffer, size_t *lenp,
150                 loff_t *ppos);
151
152 struct ctl_table;
153 int dirty_writeback_centisecs_handler(struct ctl_table *, int,
154                                       void __user *, size_t *, loff_t *);
155
156 void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
157 unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
158                                unsigned long dirty);
159
160 void __bdi_update_bandwidth(struct backing_dev_info *bdi,
161                             unsigned long thresh,
162                             unsigned long bg_thresh,
163                             unsigned long dirty,
164                             unsigned long bdi_thresh,
165                             unsigned long bdi_dirty,
166                             unsigned long start_time);
167
168 void page_writeback_init(void);
169 void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
170                                         unsigned long nr_pages_dirtied);
171
172 static inline void
173 balance_dirty_pages_ratelimited(struct address_space *mapping)
174 {
175         balance_dirty_pages_ratelimited_nr(mapping, 1);
176 }
177
178 typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
179                                 void *data);
180
181 int generic_writepages(struct address_space *mapping,
182                        struct writeback_control *wbc);
183 void tag_pages_for_writeback(struct address_space *mapping,
184                              pgoff_t start, pgoff_t end);
185 int write_cache_pages(struct address_space *mapping,
186                       struct writeback_control *wbc, writepage_t writepage,
187                       void *data);
188 int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
189 void set_page_dirty_balance(struct page *page, int page_mkwrite);
190 void writeback_set_ratelimit(void);
191 void tag_pages_for_writeback(struct address_space *mapping,
192                              pgoff_t start, pgoff_t end);
193
194 void account_page_redirty(struct page *page);
195
196 /* pdflush.c */
197 extern int nr_pdflush_threads;  /* Global so it can be exported to sysctl
198                                    read-only. */
199
200
201 #endif          /* WRITEBACK_H */