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 * A control structure which tells the writeback code what to do. These are 43 * always on the stack, and hence need no locking. They are always initialised 44 * in a manner such that unspecified fields are set to zero. 45 */ 46 struct writeback_control { 47 enum writeback_sync_modes sync_mode; 48 long nr_to_write; /* Write this many pages, and decrement 49 this for each page written */ 50 long pages_skipped; /* Pages which were not written */ 51 52 /* 53 * For a_ops->writepages(): is start or end are non-zero then this is 54 * a hint that the filesystem need only write out the pages inside that 55 * byterange. The byte at `end' is included in the writeout request. 56 */ 57 loff_t range_start; 58 loff_t range_end; 59 60 unsigned for_kupdate:1; /* A kupdate writeback */ 61 unsigned for_background:1; /* A background writeback */ 62 unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */ 63 unsigned for_reclaim:1; /* Invoked from the page allocator */ 64 unsigned range_cyclic:1; /* range_start is cyclic */ 65 }; 66 67 /* 68 * fs/fs-writeback.c 69 */ 70 struct bdi_writeback; 71 int inode_wait(void *); 72 void writeback_inodes_sb(struct super_block *); 73 void writeback_inodes_sb_nr(struct super_block *, unsigned long nr); 74 int writeback_inodes_sb_if_idle(struct super_block *); 75 int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr); 76 void sync_inodes_sb(struct super_block *); 77 long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages); 78 long wb_do_writeback(struct bdi_writeback *wb, int force_wait); 79 void wakeup_flusher_threads(long nr_pages); 80 81 /* writeback.h requires fs.h; it, too, is not included from here. */ 82 static inline void wait_on_inode(struct inode *inode) 83 { 84 might_sleep(); 85 wait_on_bit(&inode->i_state, __I_NEW, inode_wait, TASK_UNINTERRUPTIBLE); 86 } 87 static inline void inode_sync_wait(struct inode *inode) 88 { 89 might_sleep(); 90 wait_on_bit(&inode->i_state, __I_SYNC, inode_wait, 91 TASK_UNINTERRUPTIBLE); 92 } 93 94 95 /* 96 * mm/page-writeback.c 97 */ 98 #ifdef CONFIG_BLOCK 99 void laptop_io_completion(struct backing_dev_info *info); 100 void laptop_sync_completion(void); 101 void laptop_mode_sync(struct work_struct *work); 102 void laptop_mode_timer_fn(unsigned long data); 103 #else 104 static inline void laptop_sync_completion(void) { } 105 #endif 106 void throttle_vm_writeout(gfp_t gfp_mask); 107 108 extern unsigned long global_dirty_limit; 109 110 /* These are exported to sysctl. */ 111 extern int dirty_background_ratio; 112 extern unsigned long dirty_background_bytes; 113 extern int vm_dirty_ratio; 114 extern unsigned long vm_dirty_bytes; 115 extern unsigned int dirty_writeback_interval; 116 extern unsigned int dirty_expire_interval; 117 extern int vm_highmem_is_dirtyable; 118 extern int block_dump; 119 extern int laptop_mode; 120 121 extern unsigned long determine_dirtyable_memory(void); 122 123 extern int dirty_background_ratio_handler(struct ctl_table *table, int write, 124 void __user *buffer, size_t *lenp, 125 loff_t *ppos); 126 extern int dirty_background_bytes_handler(struct ctl_table *table, int write, 127 void __user *buffer, size_t *lenp, 128 loff_t *ppos); 129 extern int dirty_ratio_handler(struct ctl_table *table, int write, 130 void __user *buffer, size_t *lenp, 131 loff_t *ppos); 132 extern int dirty_bytes_handler(struct ctl_table *table, int write, 133 void __user *buffer, size_t *lenp, 134 loff_t *ppos); 135 136 struct ctl_table; 137 int dirty_writeback_centisecs_handler(struct ctl_table *, int, 138 void __user *, size_t *, loff_t *); 139 140 void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty); 141 unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, 142 unsigned long dirty); 143 144 void __bdi_update_bandwidth(struct backing_dev_info *bdi, 145 unsigned long thresh, 146 unsigned long dirty, 147 unsigned long bdi_thresh, 148 unsigned long bdi_dirty, 149 unsigned long start_time); 150 151 void page_writeback_init(void); 152 void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, 153 unsigned long nr_pages_dirtied); 154 155 static inline void 156 balance_dirty_pages_ratelimited(struct address_space *mapping) 157 { 158 balance_dirty_pages_ratelimited_nr(mapping, 1); 159 } 160 161 typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc, 162 void *data); 163 164 int generic_writepages(struct address_space *mapping, 165 struct writeback_control *wbc); 166 void tag_pages_for_writeback(struct address_space *mapping, 167 pgoff_t start, pgoff_t end); 168 int write_cache_pages(struct address_space *mapping, 169 struct writeback_control *wbc, writepage_t writepage, 170 void *data); 171 int do_writepages(struct address_space *mapping, struct writeback_control *wbc); 172 void set_page_dirty_balance(struct page *page, int page_mkwrite); 173 void writeback_set_ratelimit(void); 174 void tag_pages_for_writeback(struct address_space *mapping, 175 pgoff_t start, pgoff_t end); 176 177 /* pdflush.c */ 178 extern int nr_pdflush_threads; /* Global so it can be exported to sysctl 179 read-only. */ 180 181 182 #endif /* WRITEBACK_H */ 183