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 *);
 101void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
 102void inode_wait_for_writeback(struct inode *inode);
 103
 104/* writeback.h requires fs.h; it, too, is not included from here. */
 105static inline void wait_on_inode(struct inode *inode)
 106{
 107        might_sleep();
 108        wait_on_bit(&inode->i_state, __I_NEW, inode_wait, TASK_UNINTERRUPTIBLE);
 109}
 110
 111/*
 112 * mm/page-writeback.c
 113 */
 114#ifdef CONFIG_BLOCK
 115void laptop_io_completion(struct backing_dev_info *info);
 116void laptop_sync_completion(void);
 117void laptop_mode_sync(struct work_struct *work);
 118void laptop_mode_timer_fn(unsigned long data);
 119#else
 120static inline void laptop_sync_completion(void) { }
 121#endif
 122void throttle_vm_writeout(gfp_t gfp_mask);
 123bool zone_dirty_ok(struct zone *zone);
 124
 125extern unsigned long global_dirty_limit;
 126
 127/* These are exported to sysctl. */
 128extern int dirty_background_ratio;
 129extern unsigned long dirty_background_bytes;
 130extern int vm_dirty_ratio;
 131extern unsigned long vm_dirty_bytes;
 132extern unsigned int dirty_writeback_interval;
 133extern unsigned int dirty_expire_interval;
 134extern int vm_highmem_is_dirtyable;
 135extern int block_dump;
 136extern int laptop_mode;
 137
 138extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
 139                void __user *buffer, size_t *lenp,
 140                loff_t *ppos);
 141extern int dirty_background_bytes_handler(struct ctl_table *table, int write,
 142                void __user *buffer, size_t *lenp,
 143                loff_t *ppos);
 144extern int dirty_ratio_handler(struct ctl_table *table, int write,
 145                void __user *buffer, size_t *lenp,
 146                loff_t *ppos);
 147extern int dirty_bytes_handler(struct ctl_table *table, int write,
 148                void __user *buffer, size_t *lenp,
 149                loff_t *ppos);
 150
 151struct ctl_table;
 152int dirty_writeback_centisecs_handler(struct ctl_table *, int,
 153                                      void __user *, size_t *, loff_t *);
 154
 155void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
 156unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
 157                               unsigned long dirty);
 158
 159void __bdi_update_bandwidth(struct backing_dev_info *bdi,
 160                            unsigned long thresh,
 161                            unsigned long bg_thresh,
 162                            unsigned long dirty,
 163                            unsigned long bdi_thresh,
 164                            unsigned long bdi_dirty,
 165                            unsigned long start_time);
 166
 167void page_writeback_init(void);
 168void balance_dirty_pages_ratelimited(struct address_space *mapping);
 169
 170typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
 171                                void *data);
 172
 173int generic_writepages(struct address_space *mapping,
 174                       struct writeback_control *wbc);
 175void tag_pages_for_writeback(struct address_space *mapping,
 176                             pgoff_t start, pgoff_t end);
 177int write_cache_pages(struct address_space *mapping,
 178                      struct writeback_control *wbc, writepage_t writepage,
 179                      void *data);
 180int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
 181void set_page_dirty_balance(struct page *page, int page_mkwrite);
 182void writeback_set_ratelimit(void);
 183void tag_pages_for_writeback(struct address_space *mapping,
 184                             pgoff_t start, pgoff_t end);
 185
 186void account_page_redirty(struct page *page);
 187
 188#endif          /* WRITEBACK_H */
 189