kernel/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/workqueue.h>
   9 #include <linux/fs.h>
  10
  11 DECLARE_PER_CPU(int, dirty_throttle_leaks);
  12
  13 /*
  14  * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
  15  *
  16  *      (thresh - thresh/DIRTY_FULL_SCOPE, thresh)
  17  *
  18  * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
  19  * time) for the dirty pages to drop, unless written enough pages.
  20  *
  21  * The global dirty threshold is normally equal to the global dirty limit,
  22  * except when the system suddenly allocates a lot of anonymous memory and
  23  * knocks down the global dirty threshold quickly, in which case the global
  24  * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
  25  */
  26 #define DIRTY_SCOPE             8
  27 #define DIRTY_FULL_SCOPE        (DIRTY_SCOPE / 2)
  28
  29 struct backing_dev_info;
  30
  31 /*
  32  * fs/fs-writeback.c
  33  */
  34 enum writeback_sync_modes {
  35         WB_SYNC_NONE,   /* Don't wait on anything */
  36         WB_SYNC_ALL,    /* Wait on every mapping */
  37 };
  38
  39 /*
  40  * why some writeback work was initiated
  41  */
  42 enum wb_reason {
  43         WB_REASON_BACKGROUND,
  44         WB_REASON_TRY_TO_FREE_PAGES,
  45         WB_REASON_SYNC,
  46         WB_REASON_PERIODIC,
  47         WB_REASON_LAPTOP_TIMER,
  48         WB_REASON_FREE_MORE_MEM,
  49         WB_REASON_FS_FREE_SPACE,
  50         /*
  51          * There is no bdi forker thread any more and works are done
  52          * by emergency worker, however, this is TPs userland visible
  53          * and we'll be exposing exactly the same information,
  54          * so it has a mismatch name.
  55          */
  56         WB_REASON_FORKER_THREAD,
  57
  58         WB_REASON_MAX,
  59 };
  60
  61 /*
  62  * A control structure which tells the writeback code what to do.  These are
  63  * always on the stack, and hence need no locking.  They are always initialised
  64  * in a manner such that unspecified fields are set to zero.
  65  */
  66 struct writeback_control {
  67         long nr_to_write;               /* Write this many pages, and decrement
  68                                            this for each page written */
  69         long pages_skipped;             /* Pages which were not written */
  70
  71         /*
  72          * For a_ops->writepages(): if start or end are non-zero then this is
  73          * a hint that the filesystem need only write out the pages inside that
  74          * byterange.  The byte at `end' is included in the writeout request.
  75          */
  76         loff_t range_start;
  77         loff_t range_end;
  78
  79         enum writeback_sync_modes sync_mode;
  80
  81         unsigned for_kupdate:1;         /* A kupdate writeback */
  82         unsigned for_background:1;      /* A background writeback */
  83         unsigned tagged_writepages:1;   /* tag-and-write to avoid livelock */
  84         unsigned for_reclaim:1;         /* Invoked from the page allocator */
  85         unsigned range_cyclic:1;        /* range_start is cyclic */
  86         unsigned for_sync:1;            /* sync(2) WB_SYNC_ALL writeback */
  87 };
  88
  89 /*
  90  * fs/fs-writeback.c
  91  */
  92 struct bdi_writeback;
  93 void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
  94 void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
  95                                                         enum wb_reason reason);
  96 int try_to_writeback_inodes_sb(struct super_block *, enum wb_reason reason);
  97 int try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
  98                                   enum wb_reason reason);
  99 void sync_inodes_sb(struct super_block *);
 100 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
 101 void inode_wait_for_writeback(struct inode *inode);
 102
 103 /* writeback.h requires fs.h; it, too, is not included from here. */
 104 static inline void wait_on_inode(struct inode *inode)
 105 {
 106         might_sleep();
 107         wait_on_bit(&inode->i_state, __I_NEW, TASK_UNINTERRUPTIBLE);
 108 }
 109
 110 /*
 111  * mm/page-writeback.c
 112  */
 113 #ifdef CONFIG_BLOCK
 114 void laptop_io_completion(struct backing_dev_info *info);
 115 void laptop_sync_completion(void);
 116 void laptop_mode_sync(struct work_struct *work);
 117 void laptop_mode_timer_fn(unsigned long data);
 118 #else
 119 static inline void laptop_sync_completion(void) { }
 120 #endif
 121 void throttle_vm_writeout(gfp_t gfp_mask);
 122 bool zone_dirty_ok(struct zone *zone);
 123
 124 extern unsigned long global_dirty_limit;
 125
 126 /* These are exported to sysctl. */
 127 extern int dirty_background_ratio;
 128 extern unsigned long dirty_background_bytes;
 129 extern int vm_dirty_ratio;
 130 extern unsigned long vm_dirty_bytes;
 131 extern unsigned int dirty_writeback_interval;
 132 extern unsigned int dirty_expire_interval;
 133 extern unsigned int dirtytime_expire_interval;
 134 extern int vm_highmem_is_dirtyable;
 135 extern int block_dump;
 136 extern int laptop_mode;
 137
 138 extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
 139                 void __user *buffer, size_t *lenp,
 140                 loff_t *ppos);
 141 extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
 142                 void __user *buffer, size_t *lenp,
 143                 loff_t *ppos);
 144 extern int dirty_ratio_handler(struct ctl_table *table, int write,
 145                 void __user *buffer, size_t *lenp,
 146                 loff_t *ppos);
 147 extern int dirty_bytes_handler(struct ctl_table *table, int write,
 148                 void __user *buffer, size_t *lenp,
 149                 loff_t *ppos);
 150 int dirtytime_interval_handler(struct ctl_table *table, int write,
 151                                void __user *buffer, size_t *lenp, 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(struct address_space *mapping);
 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 writeback_set_ratelimit(void);
 184 void tag_pages_for_writeback(struct address_space *mapping,
 185                              pgoff_t start, pgoff_t end);
 186
 187 void account_page_redirty(struct page *page);
 188
 189 #endif          /* WRITEBACK_H */