include/linux/backing-dev.h

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