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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 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(): if 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. */
wait_on_inode(struct inode * inode)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 }
inode_sync_wait(struct inode * inode)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
laptop_sync_completion(void)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
balance_dirty_pages_ratelimited(struct address_space * mapping)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 */
202