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/writeback.h>
  18 #include <asm/atomic.h>
  19
  20 struct page;
  21 struct device;
  22 struct dentry;
  23
  24 /*
  25  * Bits in backing_dev_info.state
  26  */
  27 enum bdi_state {
  28         BDI_pending,            /* On its way to being activated */
  29         BDI_wb_alloc,           /* Default embedded wb allocated */
  30         BDI_async_congested,    /* The async (write) queue is getting full */
  31         BDI_sync_congested,     /* The sync queue is getting full */
  32         BDI_registered,         /* bdi_register() was done */
  33         BDI_unused,             /* Available bits start here */
  34 };
  35
  36 typedef int (congested_fn)(void *, int);
  37
  38 enum bdi_stat_item {
  39         BDI_RECLAIMABLE,
  40         BDI_WRITEBACK,
  41         NR_BDI_STAT_ITEMS
  42 };
  43
  44 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
  45
  46 struct bdi_writeback {
  47         struct list_head list;                  /* hangs off the bdi */
  48
  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
  54         struct task_struct      *task;          /* writeback task */
  55         struct list_head        b_dirty;        /* dirty inodes */
  56         struct list_head        b_io;           /* parked for writeback */
  57         struct list_head        b_more_io;      /* parked for more writeback */
  58 };
  59
  60 struct backing_dev_info {
  61         struct list_head bdi_list;
  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 update side of wb_list */
  82         struct list_head wb_list; /* the flusher threads hanging off this bdi */
  83         unsigned long wb_mask;    /* bitmask of registered tasks */
  84         unsigned int wb_cnt;      /* number of registered tasks */
  85
  86         struct list_head work_list;
  87
  88         struct device *dev;
  89
  90 #ifdef CONFIG_DEBUG_FS
  91         struct dentry *debug_dir;
  92         struct dentry *debug_stats;
  93 #endif
  94 };
  95
  96 int bdi_init(struct backing_dev_info *bdi);
  97 void bdi_destroy(struct backing_dev_info *bdi);
  98
  99 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 100                 const char *fmt, ...);
 101 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
 102 void bdi_unregister(struct backing_dev_info *bdi);
 103 void bdi_start_writeback(struct writeback_control *wbc);
 104 int bdi_writeback_task(struct bdi_writeback *wb);
 105 int bdi_has_dirty_io(struct backing_dev_info *bdi);
 106
 107 extern spinlock_t bdi_lock;
 108 extern struct list_head bdi_list;
 109
 110 static inline int wb_has_dirty_io(struct bdi_writeback *wb)
 111 {
 112         return !list_empty(&wb->b_dirty) ||
 113                !list_empty(&wb->b_io) ||
 114                !list_empty(&wb->b_more_io);
 115 }
 116
 117 static inline void __add_bdi_stat(struct backing_dev_info *bdi,
 118                 enum bdi_stat_item item, s64 amount)
 119 {
 120         __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
 121 }
 122
 123 static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
 124                 enum bdi_stat_item item)
 125 {
 126         __add_bdi_stat(bdi, item, 1);
 127 }
 128
 129 static inline void inc_bdi_stat(struct backing_dev_info *bdi,
 130                 enum bdi_stat_item item)
 131 {
 132         unsigned long flags;
 133
 134         local_irq_save(flags);
 135         __inc_bdi_stat(bdi, item);
 136         local_irq_restore(flags);
 137 }
 138
 139 static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
 140                 enum bdi_stat_item item)
 141 {
 142         __add_bdi_stat(bdi, item, -1);
 143 }
 144
 145 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
 146                 enum bdi_stat_item item)
 147 {
 148         unsigned long flags;
 149
 150         local_irq_save(flags);
 151         __dec_bdi_stat(bdi, item);
 152         local_irq_restore(flags);
 153 }
 154
 155 static inline s64 bdi_stat(struct backing_dev_info *bdi,
 156                 enum bdi_stat_item item)
 157 {
 158         return percpu_counter_read_positive(&bdi->bdi_stat[item]);
 159 }
 160
 161 static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
 162                 enum bdi_stat_item item)
 163 {
 164         return percpu_counter_sum_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         s64 sum;
 171         unsigned long flags;
 172
 173         local_irq_save(flags);
 174         sum = __bdi_stat_sum(bdi, item);
 175         local_irq_restore(flags);
 176
 177         return sum;
 178 }
 179
 180 extern void bdi_writeout_inc(struct backing_dev_info *bdi);
 181
 182 /*
 183  * maximal error of a stat counter.
 184  */
 185 static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
 186 {
 187 #ifdef CONFIG_SMP
 188         return nr_cpu_ids * BDI_STAT_BATCH;
 189 #else
 190         return 1;
 191 #endif
 192 }
 193
 194 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
 195 int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
 196
 197 /*
 198  * Flags in backing_dev_info::capability
 199  *
 200  * The first three flags control whether dirty pages will contribute to the
 201  * VM's accounting and whether writepages() should be called for dirty pages
 202  * (something that would not, for example, be appropriate for ramfs)
 203  *
 204  * WARNING: these flags are closely related and should not normally be
 205  * used separately.  The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
 206  * three flags into a single convenience macro.
 207  *
 208  * BDI_CAP_NO_ACCT_DIRTY:  Dirty pages shouldn't contribute to accounting
 209  * BDI_CAP_NO_WRITEBACK:   Don't write pages back
 210  * BDI_CAP_NO_ACCT_WB:     Don't automatically account writeback pages
 211  *
 212  * These flags let !MMU mmap() govern direct device mapping vs immediate
 213  * copying more easily for MAP_PRIVATE, especially for ROM filesystems.
 214  *
 215  * BDI_CAP_MAP_COPY:       Copy can be mapped (MAP_PRIVATE)
 216  * BDI_CAP_MAP_DIRECT:     Can be mapped directly (MAP_SHARED)
 217  * BDI_CAP_READ_MAP:       Can be mapped for reading
 218  * BDI_CAP_WRITE_MAP:      Can be mapped for writing
 219  * BDI_CAP_EXEC_MAP:       Can be mapped for execution
 220  *
 221  * BDI_CAP_SWAP_BACKED:    Count shmem/tmpfs objects as swap-backed.
 222  */
 223 #define BDI_CAP_NO_ACCT_DIRTY   0x00000001
 224 #define BDI_CAP_NO_WRITEBACK    0x00000002
 225 #define BDI_CAP_MAP_COPY        0x00000004
 226 #define BDI_CAP_MAP_DIRECT      0x00000008
 227 #define BDI_CAP_READ_MAP        0x00000010
 228 #define BDI_CAP_WRITE_MAP       0x00000020
 229 #define BDI_CAP_EXEC_MAP        0x00000040
 230 #define BDI_CAP_NO_ACCT_WB      0x00000080
 231 #define BDI_CAP_SWAP_BACKED     0x00000100
 232
 233 #define BDI_CAP_VMFLAGS \
 234         (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
 235
 236 #define BDI_CAP_NO_ACCT_AND_WRITEBACK \
 237         (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
 238
 239 #if defined(VM_MAYREAD) && \
 240         (BDI_CAP_READ_MAP != VM_MAYREAD || \
 241          BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
 242          BDI_CAP_EXEC_MAP != VM_MAYEXEC)
 243 #error please change backing_dev_info::capabilities flags
 244 #endif
 245
 246 extern struct backing_dev_info default_backing_dev_info;
 247 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
 248
 249 int writeback_in_progress(struct backing_dev_info *bdi);
 250
 251 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
 252 {
 253         if (bdi->congested_fn)
 254                 return bdi->congested_fn(bdi->congested_data, bdi_bits);
 255         return (bdi->state & bdi_bits);
 256 }
 257
 258 static inline int bdi_read_congested(struct backing_dev_info *bdi)
 259 {
 260         return bdi_congested(bdi, 1 << BDI_sync_congested);
 261 }
 262
 263 static inline int bdi_write_congested(struct backing_dev_info *bdi)
 264 {
 265         return bdi_congested(bdi, 1 << BDI_async_congested);
 266 }
 267
 268 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 269 {
 270         return bdi_congested(bdi, (1 << BDI_sync_congested) |
 271                                   (1 << BDI_async_congested));
 272 }
 273
 274 enum {
 275         BLK_RW_ASYNC    = 0,
 276         BLK_RW_SYNC     = 1,
 277 };
 278
 279 void clear_bdi_congested(struct backing_dev_info *bdi, int sync);
 280 void set_bdi_congested(struct backing_dev_info *bdi, int sync);
 281 long congestion_wait(int sync, long timeout);
 282
 283
 284 static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
 285 {
 286         return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
 287 }
 288
 289 static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
 290 {
 291         return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
 292 }
 293
 294 static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
 295 {
 296         /* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
 297         return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
 298                                       BDI_CAP_NO_WRITEBACK));
 299 }
 300
 301 static inline bool bdi_cap_swap_backed(struct backing_dev_info *bdi)
 302 {
 303         return bdi->capabilities & BDI_CAP_SWAP_BACKED;
 304 }
 305
 306 static inline bool bdi_cap_flush_forker(struct backing_dev_info *bdi)
 307 {
 308         return bdi == &default_backing_dev_info;
 309 }
 310
 311 static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
 312 {
 313         return bdi_cap_writeback_dirty(mapping->backing_dev_info);
 314 }
 315
 316 static inline bool mapping_cap_account_dirty(struct address_space *mapping)
 317 {
 318         return bdi_cap_account_dirty(mapping->backing_dev_info);
 319 }
 320
 321 static inline bool mapping_cap_swap_backed(struct address_space *mapping)
 322 {
 323         return bdi_cap_swap_backed(mapping->backing_dev_info);
 324 }
 325
 326 static inline int bdi_sched_wait(void *word)
 327 {
 328         schedule();
 329         return 0;
 330 }
 331
 332 #endif          /* _LINUX_BACKING_DEV_H */