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 */ 204