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  * 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 */