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