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