linux/include/linux/writeback.h
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   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
  10DECLARE_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
  28struct backing_dev_info;
  29
  30/*
  31 * fs/fs-writeback.c
  32 */
  33enum 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 */
  41enum 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};
  53extern 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 */
  60struct 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};
  81
  82/*
  83 * fs/fs-writeback.c
  84 */     
  85struct bdi_writeback;
  86int inode_wait(void *);
  87void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
  88void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
  89                                                        enum wb_reason reason);
  90int writeback_inodes_sb_if_idle(struct super_block *, enum wb_reason reason);
  91int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr,
  92                                                        enum wb_reason reason);
  93void sync_inodes_sb(struct super_block *);
  94long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
  95                                enum wb_reason reason);
  96long wb_do_writeback(struct bdi_writeback *wb, int force_wait);
  97void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
  98void inode_wait_for_writeback(struct inode *inode);
  99
 100/* writeback.h requires fs.h; it, too, is not included from here. */
 101static 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
 111void laptop_io_completion(struct backing_dev_info *info);
 112void laptop_sync_completion(void);
 113void laptop_mode_sync(struct work_struct *work);
 114void laptop_mode_timer_fn(unsigned long data);
 115#else
 116static inline void laptop_sync_completion(void) { }
 117#endif
 118void throttle_vm_writeout(gfp_t gfp_mask);
 119bool zone_dirty_ok(struct zone *zone);
 120
 121extern unsigned long global_dirty_limit;
 122
 123/* These are exported to sysctl. */
 124extern int dirty_background_ratio;
 125extern unsigned long dirty_background_bytes;
 126extern int vm_dirty_ratio;
 127extern unsigned long vm_dirty_bytes;
 128extern unsigned int dirty_writeback_interval;
 129extern unsigned int dirty_expire_interval;
 130extern int vm_highmem_is_dirtyable;
 131extern int block_dump;
 132extern int laptop_mode;
 133
 134extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
 135                void __user *buffer, size_t *lenp,
 136                loff_t *ppos);
 137extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
 138                void __user *buffer, size_t *lenp,
 139                loff_t *ppos);
 140extern int dirty_ratio_handler(struct ctl_table *table, int write,
 141                void __user *buffer, size_t *lenp,
 142                loff_t *ppos);
 143extern int dirty_bytes_handler(struct ctl_table *table, int write,
 144                void __user *buffer, size_t *lenp,
 145                loff_t *ppos);
 146
 147struct ctl_table;
 148int dirty_writeback_centisecs_handler(struct ctl_table *, int,
 149                                      void __user *, size_t *, loff_t *);
 150
 151void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
 152unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
 153                               unsigned long dirty);
 154
 155void __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
 163void page_writeback_init(void);
 164void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
 165                                        unsigned long nr_pages_dirtied);
 166
 167static inline void
 168balance_dirty_pages_ratelimited(struct address_space *mapping)
 169{
 170        balance_dirty_pages_ratelimited_nr(mapping, 1);
 171}
 172
 173typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
 174                                void *data);
 175
 176int generic_writepages(struct address_space *mapping,
 177                       struct writeback_control *wbc);
 178void tag_pages_for_writeback(struct address_space *mapping,
 179                             pgoff_t start, pgoff_t end);
 180int write_cache_pages(struct address_space *mapping,
 181                      struct writeback_control *wbc, writepage_t writepage,
 182                      void *data);
 183int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
 184void set_page_dirty_balance(struct page *page, int page_mkwrite);
 185void writeback_set_ratelimit(void);
 186void tag_pages_for_writeback(struct address_space *mapping,
 187                             pgoff_t start, pgoff_t end);
 188
 189void account_page_redirty(struct page *page);
 190
 191#endif          /* WRITEBACK_H */
 192
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