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