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