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, struct super_block *sb,
 105                                 long nr_pages);
 106 int bdi_writeback_task(struct bdi_writeback *wb);
 107 int bdi_has_dirty_io(struct backing_dev_info *bdi);
 108 void bdi_arm_supers_timer(void);
 109
 110 extern spinlock_t bdi_lock;
 111 extern struct list_head bdi_list;
 112
 113 static inline int wb_has_dirty_io(struct bdi_writeback *wb)
 114 {
 115         return !list_empty(&wb->b_dirty) ||
 116                !list_empty(&wb->b_io) ||
 117                !list_empty(&wb->b_more_io);
 118 }
 119
 120 static inline void __add_bdi_stat(struct backing_dev_info *bdi,
 121                 enum bdi_stat_item item, s64 amount)
 122 {
 123         __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
 124 }
 125
 126 static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
 127                 enum bdi_stat_item item)
 128 {
 129         __add_bdi_stat(bdi, item, 1);
 130 }
 131
 132 static inline void inc_bdi_stat(struct backing_dev_info *bdi,
 133                 enum bdi_stat_item item)
 134 {
 135         unsigned long flags;
 136
 137         local_irq_save(flags);
 138         __inc_bdi_stat(bdi, item);
 139         local_irq_restore(flags);
 140 }
 141
 142 static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
 143                 enum bdi_stat_item item)
 144 {
 145         __add_bdi_stat(bdi, item, -1);
 146 }
 147
 148 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
 149                 enum bdi_stat_item item)
 150 {
 151         unsigned long flags;
 152
 153         local_irq_save(flags);
 154         __dec_bdi_stat(bdi, item);
 155         local_irq_restore(flags);
 156 }
 157
 158 static inline s64 bdi_stat(struct backing_dev_info *bdi,
 159                 enum bdi_stat_item item)
 160 {
 161         return percpu_counter_read_positive(&bdi->bdi_stat[item]);
 162 }
 163
 164 static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
 165                 enum bdi_stat_item item)
 166 {
 167         return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
 168 }
 169
 170 static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
 171                 enum bdi_stat_item item)
 172 {
 173         s64 sum;
 174         unsigned long flags;
 175
 176         local_irq_save(flags);
 177         sum = __bdi_stat_sum(bdi, item);
 178         local_irq_restore(flags);
 179
 180         return sum;
 181 }
 182
 183 extern void bdi_writeout_inc(struct backing_dev_info *bdi);
 184
 185 /*
 186  * maximal error of a stat counter.
 187  */
 188 static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
 189 {
 190 #ifdef CONFIG_SMP
 191         return nr_cpu_ids * BDI_STAT_BATCH;
 192 #else
 193         return 1;
 194 #endif
 195 }
 196
 197 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
 198 int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
 199
 200 /*
 201  * Flags in backing_dev_info::capability
 202  *
 203  * The first three flags control whether dirty pages will contribute to the
 204  * VM's accounting and whether writepages() should be called for dirty pages
 205  * (something that would not, for example, be appropriate for ramfs)
 206  *
 207  * WARNING: these flags are closely related and should not normally be
 208  * used separately.  The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
 209  * three flags into a single convenience macro.
 210  *
 211  * BDI_CAP_NO_ACCT_DIRTY:  Dirty pages shouldn't contribute to accounting
 212  * BDI_CAP_NO_WRITEBACK:   Don't write pages back
 213  * BDI_CAP_NO_ACCT_WB:     Don't automatically account writeback pages
 214  *
 215  * These flags let !MMU mmap() govern direct device mapping vs immediate
 216  * copying more easily for MAP_PRIVATE, especially for ROM filesystems.
 217  *
 218  * BDI_CAP_MAP_COPY:       Copy can be mapped (MAP_PRIVATE)
 219  * BDI_CAP_MAP_DIRECT:     Can be mapped directly (MAP_SHARED)
 220  * BDI_CAP_READ_MAP:       Can be mapped for reading
 221  * BDI_CAP_WRITE_MAP:      Can be mapped for writing
 222  * BDI_CAP_EXEC_MAP:       Can be mapped for execution
 223  *
 224  * BDI_CAP_SWAP_BACKED:    Count shmem/tmpfs objects as swap-backed.
 225  */
 226 #define BDI_CAP_NO_ACCT_DIRTY   0x00000001
 227 #define BDI_CAP_NO_WRITEBACK    0x00000002
 228 #define BDI_CAP_MAP_COPY        0x00000004
 229 #define BDI_CAP_MAP_DIRECT      0x00000008
 230 #define BDI_CAP_READ_MAP        0x00000010
 231 #define BDI_CAP_WRITE_MAP       0x00000020
 232 #define BDI_CAP_EXEC_MAP        0x00000040
 233 #define BDI_CAP_NO_ACCT_WB      0x00000080
 234 #define BDI_CAP_SWAP_BACKED     0x00000100
 235
 236 #define BDI_CAP_VMFLAGS \
 237         (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
 238
 239 #define BDI_CAP_NO_ACCT_AND_WRITEBACK \
 240         (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
 241
 242 #if defined(VM_MAYREAD) && \
 243         (BDI_CAP_READ_MAP != VM_MAYREAD || \
 244          BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
 245          BDI_CAP_EXEC_MAP != VM_MAYEXEC)
 246 #error please change backing_dev_info::capabilities flags
 247 #endif
 248
 249 extern struct backing_dev_info default_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 #endif          /* _LINUX_BACKING_DEV_H */