linux/include/linux/backing-dev.h
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   1/*
   2 * include/linux/backing-dev.h
   3 *
   4 * low-level device information and state which is propagated up through
   5 * to high-level code.
   6 */
   7
   8#ifndef _LINUX_BACKING_DEV_H
   9#define _LINUX_BACKING_DEV_H
  10
  11#include <linux/percpu_counter.h>
  12#include <linux/log2.h>
  13#include <linux/flex_proportions.h>
  14#include <linux/kernel.h>
  15#include <linux/fs.h>
  16#include <linux/sched.h>
  17#include <linux/timer.h>
  18#include <linux/writeback.h>
  19#include <linux/atomic.h>
  20#include <linux/sysctl.h>
  21
  22struct page;
  23struct device;
  24struct dentry;
  25
  26/*
  27 * Bits in backing_dev_info.state
  28 */
  29enum bdi_state {
  30        BDI_pending,            /* On its way to being activated */
  31        BDI_wb_alloc,           /* Default embedded wb allocated */
  32        BDI_async_congested,    /* The async (write) queue is getting full */
  33        BDI_sync_congested,     /* The sync queue is getting full */
  34        BDI_registered,         /* bdi_register() was done */
  35        BDI_writeback_running,  /* Writeback is in progress */
  36        BDI_unused,             /* Available bits start here */
  37};
  38
  39typedef int (congested_fn)(void *, int);
  40
  41enum bdi_stat_item {
  42        BDI_RECLAIMABLE,
  43        BDI_WRITEBACK,
  44        BDI_DIRTIED,
  45        BDI_WRITTEN,
  46        NR_BDI_STAT_ITEMS
  47};
  48
  49#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
  50
  51struct bdi_writeback {
  52        struct backing_dev_info *bdi;   /* our parent bdi */
  53        unsigned int nr;
  54
  55        unsigned long last_old_flush;   /* last old data flush */
  56        unsigned long last_active;      /* last time bdi thread was active */
  57
  58        struct task_struct *task;       /* writeback thread */
  59        struct timer_list wakeup_timer; /* used for delayed bdi thread wakeup */
  60        struct list_head b_dirty;       /* dirty inodes */
  61        struct list_head b_io;          /* parked for writeback */
  62        struct list_head b_more_io;     /* parked for more writeback */
  63        spinlock_t list_lock;           /* protects the b_* lists */
  64};
  65
  66struct backing_dev_info {
  67        struct list_head bdi_list;
  68        unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
  69        unsigned long state;    /* Always use atomic bitops on this */
  70        unsigned int capabilities; /* Device capabilities */
  71        congested_fn *congested_fn; /* Function pointer if device is md/dm */
  72        void *congested_data;   /* Pointer to aux data for congested func */
  73
  74        char *name;
  75
  76        struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
  77
  78        unsigned long bw_time_stamp;    /* last time write bw is updated */
  79        unsigned long dirtied_stamp;
  80        unsigned long written_stamp;    /* pages written at bw_time_stamp */
  81        unsigned long write_bandwidth;  /* the estimated write bandwidth */
  82        unsigned long avg_write_bandwidth; /* further smoothed write bw */
  83
  84        /*
  85         * The base dirty throttle rate, re-calculated on every 200ms.
  86         * All the bdi tasks' dirty rate will be curbed under it.
  87         * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
  88         * in small steps and is much more smooth/stable than the latter.
  89         */
  90        unsigned long dirty_ratelimit;
  91        unsigned long balanced_dirty_ratelimit;
  92
  93        struct fprop_local_percpu completions;
  94        int dirty_exceeded;
  95
  96        unsigned int min_ratio;
  97        unsigned int max_ratio, max_prop_frac;
  98
  99        struct bdi_writeback wb;  /* default writeback info for this bdi */
 100        spinlock_t wb_lock;       /* protects work_list */
 101
 102        struct list_head work_list;
 103
 104        struct device *dev;
 105
 106        struct timer_list laptop_mode_wb_timer;
 107
 108#ifdef CONFIG_DEBUG_FS
 109        struct dentry *debug_dir;
 110        struct dentry *debug_stats;
 111#endif
 112};
 113
 114int bdi_init(struct backing_dev_info *bdi);
 115void bdi_destroy(struct backing_dev_info *bdi);
 116
 117int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 118                const char *fmt, ...);
 119int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
 120void bdi_unregister(struct backing_dev_info *bdi);
 121int bdi_setup_and_register(struct backing_dev_info *, char *, unsigned int);
 122void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
 123                        enum wb_reason reason);
 124void bdi_start_background_writeback(struct backing_dev_info *bdi);
 125int bdi_writeback_thread(void *data);
 126int bdi_has_dirty_io(struct backing_dev_info *bdi);
 127void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi);
 128void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2);
 129
 130extern spinlock_t bdi_lock;
 131extern struct list_head bdi_list;
 132extern struct list_head bdi_pending_list;
 133
 134static inline int wb_has_dirty_io(struct bdi_writeback *wb)
 135{
 136        return !list_empty(&wb->b_dirty) ||
 137               !list_empty(&wb->b_io) ||
 138               !list_empty(&wb->b_more_io);
 139}
 140
 141static inline void __add_bdi_stat(struct backing_dev_info *bdi,
 142                enum bdi_stat_item item, s64 amount)
 143{
 144        __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
 145}
 146
 147static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
 148                enum bdi_stat_item item)
 149{
 150        __add_bdi_stat(bdi, item, 1);
 151}
 152
 153static inline void inc_bdi_stat(struct backing_dev_info *bdi,
 154                enum bdi_stat_item item)
 155{
 156        unsigned long flags;
 157
 158        local_irq_save(flags);
 159        __inc_bdi_stat(bdi, item);
 160        local_irq_restore(flags);
 161}
 162
 163static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
 164                enum bdi_stat_item item)
 165{
 166        __add_bdi_stat(bdi, item, -1);
 167}
 168
 169static inline void dec_bdi_stat(struct backing_dev_info *bdi,
 170                enum bdi_stat_item item)
 171{
 172        unsigned long flags;
 173
 174        local_irq_save(flags);
 175        __dec_bdi_stat(bdi, item);
 176        local_irq_restore(flags);
 177}
 178
 179static inline s64 bdi_stat(struct backing_dev_info *bdi,
 180                enum bdi_stat_item item)
 181{
 182        return percpu_counter_read_positive(&bdi->bdi_stat[item]);
 183}
 184
 185static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
 186                enum bdi_stat_item item)
 187{
 188        return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
 189}
 190
 191static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
 192                enum bdi_stat_item item)
 193{
 194        s64 sum;
 195        unsigned long flags;
 196
 197        local_irq_save(flags);
 198        sum = __bdi_stat_sum(bdi, item);
 199        local_irq_restore(flags);
 200
 201        return sum;
 202}
 203
 204extern void bdi_writeout_inc(struct backing_dev_info *bdi);
 205
 206/*
 207 * maximal error of a stat counter.
 208 */
 209static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
 210{
 211#ifdef CONFIG_SMP
 212        return nr_cpu_ids * BDI_STAT_BATCH;
 213#else
 214        return 1;
 215#endif
 216}
 217
 218int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
 219int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
 220
 221/*
 222 * Flags in backing_dev_info::capability
 223 *
 224 * The first three flags control whether dirty pages will contribute to the
 225 * VM's accounting and whether writepages() should be called for dirty pages
 226 * (something that would not, for example, be appropriate for ramfs)
 227 *
 228 * WARNING: these flags are closely related and should not normally be
 229 * used separately.  The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
 230 * three flags into a single convenience macro.
 231 *
 232 * BDI_CAP_NO_ACCT_DIRTY:  Dirty pages shouldn't contribute to accounting
 233 * BDI_CAP_NO_WRITEBACK:   Don't write pages back
 234 * BDI_CAP_NO_ACCT_WB:     Don't automatically account writeback pages
 235 *
 236 * These flags let !MMU mmap() govern direct device mapping vs immediate
 237 * copying more easily for MAP_PRIVATE, especially for ROM filesystems.
 238 *
 239 * BDI_CAP_MAP_COPY:       Copy can be mapped (MAP_PRIVATE)
 240 * BDI_CAP_MAP_DIRECT:     Can be mapped directly (MAP_SHARED)
 241 * BDI_CAP_READ_MAP:       Can be mapped for reading
 242 * BDI_CAP_WRITE_MAP:      Can be mapped for writing
 243 * BDI_CAP_EXEC_MAP:       Can be mapped for execution
 244 *
 245 * BDI_CAP_SWAP_BACKED:    Count shmem/tmpfs objects as swap-backed.
 246 */
 247#define BDI_CAP_NO_ACCT_DIRTY   0x00000001
 248#define BDI_CAP_NO_WRITEBACK    0x00000002
 249#define BDI_CAP_MAP_COPY        0x00000004
 250#define BDI_CAP_MAP_DIRECT      0x00000008
 251#define BDI_CAP_READ_MAP        0x00000010
 252#define BDI_CAP_WRITE_MAP       0x00000020
 253#define BDI_CAP_EXEC_MAP        0x00000040
 254#define BDI_CAP_NO_ACCT_WB      0x00000080
 255#define BDI_CAP_SWAP_BACKED     0x00000100
 256
 257#define BDI_CAP_VMFLAGS \
 258        (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
 259
 260#define BDI_CAP_NO_ACCT_AND_WRITEBACK \
 261        (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
 262
 263#if defined(VM_MAYREAD) && \
 264        (BDI_CAP_READ_MAP != VM_MAYREAD || \
 265         BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
 266         BDI_CAP_EXEC_MAP != VM_MAYEXEC)
 267#error please change backing_dev_info::capabilities flags
 268#endif
 269
 270extern struct backing_dev_info default_backing_dev_info;
 271extern struct backing_dev_info noop_backing_dev_info;
 272
 273int writeback_in_progress(struct backing_dev_info *bdi);
 274
 275static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
 276{
 277        if (bdi->congested_fn)
 278                return bdi->congested_fn(bdi->congested_data, bdi_bits);
 279        return (bdi->state & bdi_bits);
 280}
 281
 282static inline int bdi_read_congested(struct backing_dev_info *bdi)
 283{
 284        return bdi_congested(bdi, 1 << BDI_sync_congested);
 285}
 286
 287static inline int bdi_write_congested(struct backing_dev_info *bdi)
 288{
 289        return bdi_congested(bdi, 1 << BDI_async_congested);
 290}
 291
 292static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 293{
 294        return bdi_congested(bdi, (1 << BDI_sync_congested) |
 295                                  (1 << BDI_async_congested));
 296}
 297
 298enum {
 299        BLK_RW_ASYNC    = 0,
 300        BLK_RW_SYNC     = 1,
 301};
 302
 303void clear_bdi_congested(struct backing_dev_info *bdi, int sync);
 304void set_bdi_congested(struct backing_dev_info *bdi, int sync);
 305long congestion_wait(int sync, long timeout);
 306long wait_iff_congested(struct zone *zone, int sync, long timeout);
 307int pdflush_proc_obsolete(struct ctl_table *table, int write,
 308                void __user *buffer, size_t *lenp, loff_t *ppos);
 309
 310static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
 311{
 312        return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
 313}
 314
 315static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
 316{
 317        return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
 318}
 319
 320static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
 321{
 322        /* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
 323        return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
 324                                      BDI_CAP_NO_WRITEBACK));
 325}
 326
 327static inline bool bdi_cap_swap_backed(struct backing_dev_info *bdi)
 328{
 329        return bdi->capabilities & BDI_CAP_SWAP_BACKED;
 330}
 331
 332static inline bool bdi_cap_flush_forker(struct backing_dev_info *bdi)
 333{
 334        return bdi == &default_backing_dev_info;
 335}
 336
 337static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
 338{
 339        return bdi_cap_writeback_dirty(mapping->backing_dev_info);
 340}
 341
 342static inline bool mapping_cap_account_dirty(struct address_space *mapping)
 343{
 344        return bdi_cap_account_dirty(mapping->backing_dev_info);
 345}
 346
 347static inline bool mapping_cap_swap_backed(struct address_space *mapping)
 348{
 349        return bdi_cap_swap_backed(mapping->backing_dev_info);
 350}
 351
 352static inline int bdi_sched_wait(void *word)
 353{
 354        schedule();
 355        return 0;
 356}
 357
 358#endif          /* _LINUX_BACKING_DEV_H */
 359
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