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 /*
  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 int dirty_background_ratio_handler(struct ctl_table *table, int write,
 142                 void __user *buffer, size_t *lenp,
 143                 loff_t *ppos);
 144 extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
 145                 void __user *buffer, size_t *lenp,
 146                 loff_t *ppos);
 147 extern int dirty_ratio_handler(struct ctl_table *table, int write,
 148                 void __user *buffer, size_t *lenp,
 149                 loff_t *ppos);
 150 extern int dirty_bytes_handler(struct ctl_table *table, int write,
 151                 void __user *buffer, size_t *lenp,
 152                 loff_t *ppos);
 153
 154 struct ctl_table;
 155 int dirty_writeback_centisecs_handler(struct ctl_table *, int,
 156                                       void __user *, size_t *, loff_t *);
 157
 158 void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
 159 unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
 160                                unsigned long dirty);
 161
 162 void __bdi_update_bandwidth(struct backing_dev_info *bdi,
 163                             unsigned long thresh,
 164                             unsigned long bg_thresh,
 165                             unsigned long dirty,
 166                             unsigned long bdi_thresh,
 167                             unsigned long bdi_dirty,
 168                             unsigned long start_time);
 169
 170 void page_writeback_init(void);
 171 void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
 172                                         unsigned long nr_pages_dirtied);
 173
 174 static inline void
 175 balance_dirty_pages_ratelimited(struct address_space *mapping)
 176 {
 177         balance_dirty_pages_ratelimited_nr(mapping, 1);
 178 }
 179
 180 typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
 181                                 void *data);
 182
 183 int generic_writepages(struct address_space *mapping,
 184                        struct writeback_control *wbc);
 185 void tag_pages_for_writeback(struct address_space *mapping,
 186                              pgoff_t start, pgoff_t end);
 187 int write_cache_pages(struct address_space *mapping,
 188                       struct writeback_control *wbc, writepage_t writepage,
 189                       void *data);
 190 int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
 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 */