LXR linux/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
  11DECLARE_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
  29struct backing_dev_info;
  30
  31/*
  32 * fs/fs-writeback.c
  33 */
  34enum 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 */
  42enum 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 */
  66struct 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 */     
  92struct bdi_writeback;
  93int inode_wait(void *);
  94void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
  95void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
  96                                                        enum wb_reason reason);
  97int try_to_writeback_inodes_sb(struct super_block *, enum wb_reason reason);
  98int try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
  99                                  enum wb_reason reason);
 100void sync_inodes_sb(struct super_block *);
 101long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
 102                                enum wb_reason reason);
 103void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
 104void inode_wait_for_writeback(struct inode *inode);
 105
 106/* writeback.h requires fs.h; it, too, is not included from here. */
 107static inline void wait_on_inode(struct inode *inode)
 108{
 109        might_sleep();
 110        wait_on_bit(&inode->i_state, __I_NEW, inode_wait, TASK_UNINTERRUPTIBLE);
 111}
 112
 113/*
 114 * mm/page-writeback.c
 115 */
 116#ifdef CONFIG_BLOCK
 117void laptop_io_completion(struct backing_dev_info *info);
 118void laptop_sync_completion(void);
 119void laptop_mode_sync(struct work_struct *work);
 120void laptop_mode_timer_fn(unsigned long data);
 121#else
 122static inline void laptop_sync_completion(void) { }
 123#endif
 124void throttle_vm_writeout(gfp_t gfp_mask);
 125bool zone_dirty_ok(struct zone *zone);
 126
 127extern unsigned long global_dirty_limit;
 128
 129/* These are exported to sysctl. */
 130extern int dirty_background_ratio;
 131extern unsigned long dirty_background_bytes;
 132extern int vm_dirty_ratio;
 133extern unsigned long vm_dirty_bytes;
 134extern unsigned int dirty_writeback_interval;
 135extern unsigned int dirty_expire_interval;
 136extern int vm_highmem_is_dirtyable;
 137extern int block_dump;
 138extern int laptop_mode;
 139
 140extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
 141                void __user *buffer, size_t *lenp,
 142                loff_t *ppos);
 143extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
 144                void __user *buffer, size_t *lenp,
 145                loff_t *ppos);
 146extern int dirty_ratio_handler(struct ctl_table *table, int write,
 147                void __user *buffer, size_t *lenp,
 148                loff_t *ppos);
 149extern int dirty_bytes_handler(struct ctl_table *table, int write,
 150                void __user *buffer, size_t *lenp,
 151                loff_t *ppos);
 152
 153struct ctl_table;
 154int dirty_writeback_centisecs_handler(struct ctl_table *, int,
 155                                      void __user *, size_t *, loff_t *);
 156
 157void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
 158unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
 159                               unsigned long dirty);
 160
 161void __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
 169void page_writeback_init(void);
 170void balance_dirty_pages_ratelimited(struct address_space *mapping);
 171
 172typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
 173                                void *data);
 174
 175int generic_writepages(struct address_space *mapping,
 176                       struct writeback_control *wbc);
 177void tag_pages_for_writeback(struct address_space *mapping,
 178                             pgoff_t start, pgoff_t end);
 179int write_cache_pages(struct address_space *mapping,
 180                      struct writeback_control *wbc, writepage_t writepage,
 181                      void *data);
 182int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
 183void set_page_dirty_balance(struct page *page, int page_mkwrite);
 184void writeback_set_ratelimit(void);
 185void tag_pages_for_writeback(struct address_space *mapping,
 186                             pgoff_t start, pgoff_t end);
 187
 188void account_page_redirty(struct page *page);
 189
 190#endif          /* WRITEBACK_H */
 191