a378c295851f8cf9fe4d804080b30f72cf5101cd
[pandora-kernel.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 /*
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
31 struct backing_dev_info;
32
33 /*
34  * fs/fs-writeback.c
35  */
36 enum 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  */
44 enum 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 };
56 extern 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  */
63 struct 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  */     
87 struct bdi_writeback;
88 int inode_wait(void *);
89 void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
90 void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
91                                                         enum wb_reason reason);
92 int writeback_inodes_sb_if_idle(struct super_block *, enum wb_reason reason);
93 int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr,
94                                                         enum wb_reason reason);
95 void sync_inodes_sb(struct super_block *);
96 long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
97                                 enum wb_reason reason);
98 long wb_do_writeback(struct bdi_writeback *wb, int force_wait);
99 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
100
101 /* writeback.h requires fs.h; it, too, is not included from here. */
102 static 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 }
107 static 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
119 void laptop_io_completion(struct backing_dev_info *info);
120 void laptop_sync_completion(void);
121 void laptop_mode_sync(struct work_struct *work);
122 void laptop_mode_timer_fn(unsigned long data);
123 #else
124 static inline void laptop_sync_completion(void) { }
125 #endif
126 void throttle_vm_writeout(gfp_t gfp_mask);
127
128 extern unsigned long global_dirty_limit;
129
130 /* These are exported to sysctl. */
131 extern int dirty_background_ratio;
132 extern unsigned long dirty_background_bytes;
133 extern int vm_dirty_ratio;
134 extern unsigned long vm_dirty_bytes;
135 extern unsigned int dirty_writeback_interval;
136 extern unsigned int dirty_expire_interval;
137 extern int vm_highmem_is_dirtyable;
138 extern int block_dump;
139 extern int laptop_mode;
140
141 extern unsigned long determine_dirtyable_memory(void);
142
143 extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
144                 void __user *buffer, size_t *lenp,
145                 loff_t *ppos);
146 extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
147                 void __user *buffer, size_t *lenp,
148                 loff_t *ppos);
149 extern int dirty_ratio_handler(struct ctl_table *table, int write,
150                 void __user *buffer, size_t *lenp,
151                 loff_t *ppos);
152 extern int dirty_bytes_handler(struct ctl_table *table, int write,
153                 void __user *buffer, size_t *lenp,
154                 loff_t *ppos);
155
156 struct ctl_table;
157 int dirty_writeback_centisecs_handler(struct ctl_table *, int,
158                                       void __user *, size_t *, loff_t *);
159
160 void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
161 unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
162                                unsigned long dirty);
163
164 void __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
172 void page_writeback_init(void);
173 void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
174                                         unsigned long nr_pages_dirtied);
175
176 static inline void
177 balance_dirty_pages_ratelimited(struct address_space *mapping)
178 {
179         balance_dirty_pages_ratelimited_nr(mapping, 1);
180 }
181
182 typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
183                                 void *data);
184
185 int generic_writepages(struct address_space *mapping,
186                        struct writeback_control *wbc);
187 void tag_pages_for_writeback(struct address_space *mapping,
188                              pgoff_t start, pgoff_t end);
189 int write_cache_pages(struct address_space *mapping,
190                       struct writeback_control *wbc, writepage_t writepage,
191                       void *data);
192 int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
193 void set_page_dirty_balance(struct page *page, int page_mkwrite);
194 void writeback_set_ratelimit(void);
195 void tag_pages_for_writeback(struct address_space *mapping,
196                              pgoff_t start, pgoff_t end);
197
198 /* pdflush.c */
199 extern int nr_pdflush_threads;  /* Global so it can be exported to sysctl
200                                    read-only. */
201
202
203 #endif          /* WRITEBACK_H */