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         WB_REASON_FORKER_THREAD,
  51
  52         WB_REASON_MAX,
  53 };
  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         long nr_to_write;               /* Write this many pages, and decrement
  62                                            this for each page written */
  63         long pages_skipped;             /* Pages which were not written */
  64
  65         /*
  66          * For a_ops->writepages(): if start or end are non-zero then this is
  67          * a hint that the filesystem need only write out the pages inside that
  68          * byterange.  The byte at `end' is included in the writeout request.
  69          */
  70         loff_t range_start;
  71         loff_t range_end;
  72
  73         enum writeback_sync_modes sync_mode;
  74
  75         unsigned for_kupdate:1;         /* A kupdate writeback */
  76         unsigned for_background:1;      /* A background writeback */
  77         unsigned tagged_writepages:1;   /* tag-and-write to avoid livelock */
  78         unsigned for_reclaim:1;         /* Invoked from the page allocator */
  79         unsigned range_cyclic:1;        /* range_start is cyclic */
  80         unsigned for_sync:1;            /* sync(2) WB_SYNC_ALL writeback */
  81 };
  82
  83 /*
  84  * fs/fs-writeback.c
  85  */
  86 struct bdi_writeback;
  87 int inode_wait(void *);
  88 void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
  89 void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
  90                                                         enum wb_reason reason);
  91 int try_to_writeback_inodes_sb(struct super_block *, enum wb_reason reason);
  92 int try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
  93                                   enum wb_reason reason);
  94 void sync_inodes_sb(struct super_block *);
  95 long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
  96                                 enum wb_reason reason);
  97 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
  98 void inode_wait_for_writeback(struct inode *inode);
  99
 100 /* writeback.h requires fs.h; it, too, is not included from here. */
 101 static inline void wait_on_inode(struct inode *inode)
 102 {
 103         might_sleep();
 104         wait_on_bit(&inode->i_state, __I_NEW, inode_wait, TASK_UNINTERRUPTIBLE);
 105 }
 106
 107 /*
 108  * mm/page-writeback.c
 109  */
 110 #ifdef CONFIG_BLOCK
 111 void laptop_io_completion(struct backing_dev_info *info);
 112 void laptop_sync_completion(void);
 113 void laptop_mode_sync(struct work_struct *work);
 114 void laptop_mode_timer_fn(unsigned long data);
 115 #else
 116 static inline void laptop_sync_completion(void) { }
 117 #endif
 118 void throttle_vm_writeout(gfp_t gfp_mask);
 119 bool zone_dirty_ok(struct zone *zone);
 120
 121 extern unsigned long global_dirty_limit;
 122
 123 /* These are exported to sysctl. */
 124 extern int dirty_background_ratio;
 125 extern unsigned long dirty_background_bytes;
 126 extern int vm_dirty_ratio;
 127 extern unsigned long vm_dirty_bytes;
 128 extern unsigned int dirty_writeback_interval;
 129 extern unsigned int dirty_expire_interval;
 130 extern int vm_highmem_is_dirtyable;
 131 extern int block_dump;
 132 extern int laptop_mode;
 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 bg_thresh,
 158                             unsigned long dirty,
 159                             unsigned long bdi_thresh,
 160                             unsigned long bdi_dirty,
 161                             unsigned long start_time);
 162
 163 void page_writeback_init(void);
 164 void balance_dirty_pages_ratelimited(struct address_space *mapping);
 165
 166 typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
 167                                 void *data);
 168
 169 int generic_writepages(struct address_space *mapping,
 170                        struct writeback_control *wbc);
 171 void tag_pages_for_writeback(struct address_space *mapping,
 172                              pgoff_t start, pgoff_t end);
 173 int write_cache_pages(struct address_space *mapping,
 174                       struct writeback_control *wbc, writepage_t writepage,
 175                       void *data);
 176 int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
 177 void set_page_dirty_balance(struct page *page, int page_mkwrite);
 178 void writeback_set_ratelimit(void);
 179 void tag_pages_for_writeback(struct address_space *mapping,
 180                              pgoff_t start, pgoff_t end);
 181
 182 void account_page_redirty(struct page *page);
 183
 184 #endif          /* WRITEBACK_H */