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 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(): is 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. */
  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 }
 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
 121 static inline void laptop_sync_completion(void) { }
 122 #endif
 123 void throttle_vm_writeout(gfp_t gfp_mask);
 124
 125 extern unsigned long global_dirty_limit;
 126
 127 /* These are exported to sysctl. */
 128 extern int dirty_background_ratio;
 129 extern unsigned long dirty_background_bytes;
 130 extern int vm_dirty_ratio;
 131 extern unsigned long vm_dirty_bytes;
 132 extern unsigned int dirty_writeback_interval;
 133 extern unsigned int dirty_expire_interval;
 134 extern int vm_highmem_is_dirtyable;
 135 extern int block_dump;
 136 extern int laptop_mode;
 137
 138 extern unsigned long determine_dirtyable_memory(void);
 139
 140 extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
 141                 void __user *buffer, size_t *lenp,
 142                 loff_t *ppos);
 143 extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
 144                 void __user *buffer, size_t *lenp,
 145                 loff_t *ppos);
 146 extern int dirty_ratio_handler(struct ctl_table *table, int write,
 147                 void __user *buffer, size_t *lenp,
 148                 loff_t *ppos);
 149 extern int dirty_bytes_handler(struct ctl_table *table, int write,
 150                 void __user *buffer, size_t *lenp,
 151                 loff_t *ppos);
 152
 153 struct ctl_table;
 154 int dirty_writeback_centisecs_handler(struct ctl_table *, int,
 155                                       void __user *, size_t *, loff_t *);
 156
 157 void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
 158 unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
 159                                unsigned long dirty);
 160
 161 void __bdi_update_bandwidth(struct backing_dev_info *bdi,
 162                             unsigned long thresh,
 163                             unsigned long bg_thresh,
 164                             unsigned long dirty,
 165                             unsigned long bdi_thresh,
 166                             unsigned long bdi_dirty,
 167                             unsigned long start_time);
 168
 169 void page_writeback_init(void);
 170 void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
 171                                         unsigned long nr_pages_dirtied);
 172
 173 static inline void
 174 balance_dirty_pages_ratelimited(struct address_space *mapping)
 175 {
 176         balance_dirty_pages_ratelimited_nr(mapping, 1);
 177 }
 178
 179 typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
 180                                 void *data);
 181
 182 int generic_writepages(struct address_space *mapping,
 183                        struct writeback_control *wbc);
 184 void tag_pages_for_writeback(struct address_space *mapping,
 185                              pgoff_t start, pgoff_t end);
 186 int write_cache_pages(struct address_space *mapping,
 187                       struct writeback_control *wbc, writepage_t writepage,
 188                       void *data);
 189 int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
 190 void set_page_dirty_balance(struct page *page, int page_mkwrite);
 191 void writeback_set_ratelimit(void);
 192 void tag_pages_for_writeback(struct address_space *mapping,
 193                              pgoff_t start, pgoff_t end);
 194
 195 void account_page_redirty(struct page *page);
 196
 197 /* pdflush.c */
 198 extern int nr_pdflush_threads;  /* Global so it can be exported to sysctl
 199                                    read-only. */
 200
 201
 202 #endif          /* WRITEBACK_H */