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 <asm/atomic.h>
  17
  18 struct page;
  19 struct device;
  20 struct dentry;
  21
  22 /*
  23  * Bits in backing_dev_info.state
  24  */
  25 enum bdi_state {
  26         BDI_pdflush,            /* A pdflush thread is working this device */
  27         BDI_async_congested,    /* The async (write) queue is getting full */
  28         BDI_sync_congested,     /* The sync queue is getting full */
  29         BDI_unused,             /* Available bits start here */
  30 };
  31
  32 typedef int (congested_fn)(void *, int);
  33
  34 enum bdi_stat_item {
  35         BDI_RECLAIMABLE,
  36         BDI_WRITEBACK,
  37         NR_BDI_STAT_ITEMS
  38 };
  39
  40 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
  41
  42 struct backing_dev_info {
  43         unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
  44         unsigned long state;    /* Always use atomic bitops on this */
  45         unsigned int capabilities; /* Device capabilities */
  46         congested_fn *congested_fn; /* Function pointer if device is md/dm */
  47         void *congested_data;   /* Pointer to aux data for congested func */
  48         void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
  49         void *unplug_io_data;
  50
  51         struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
  52
  53         struct prop_local_percpu completions;
  54         int dirty_exceeded;
  55
  56         unsigned int min_ratio;
  57         unsigned int max_ratio, max_prop_frac;
  58
  59         struct device *dev;
  60
  61 #ifdef CONFIG_DEBUG_FS
  62         struct dentry *debug_dir;
  63         struct dentry *debug_stats;
  64 #endif
  65 };
  66
  67 int bdi_init(struct backing_dev_info *bdi);
  68 void bdi_destroy(struct backing_dev_info *bdi);
  69
  70 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
  71                 const char *fmt, ...);
  72 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
  73 void bdi_unregister(struct backing_dev_info *bdi);
  74
  75 static inline void __add_bdi_stat(struct backing_dev_info *bdi,
  76                 enum bdi_stat_item item, s64 amount)
  77 {
  78         __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
  79 }
  80
  81 static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
  82                 enum bdi_stat_item item)
  83 {
  84         __add_bdi_stat(bdi, item, 1);
  85 }
  86
  87 static inline void inc_bdi_stat(struct backing_dev_info *bdi,
  88                 enum bdi_stat_item item)
  89 {
  90         unsigned long flags;
  91
  92         local_irq_save(flags);
  93         __inc_bdi_stat(bdi, item);
  94         local_irq_restore(flags);
  95 }
  96
  97 static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
  98                 enum bdi_stat_item item)
  99 {
 100         __add_bdi_stat(bdi, item, -1);
 101 }
 102
 103 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
 104                 enum bdi_stat_item item)
 105 {
 106         unsigned long flags;
 107
 108         local_irq_save(flags);
 109         __dec_bdi_stat(bdi, item);
 110         local_irq_restore(flags);
 111 }
 112
 113 static inline s64 bdi_stat(struct backing_dev_info *bdi,
 114                 enum bdi_stat_item item)
 115 {
 116         return percpu_counter_read_positive(&bdi->bdi_stat[item]);
 117 }
 118
 119 static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
 120                 enum bdi_stat_item item)
 121 {
 122         return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
 123 }
 124
 125 static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
 126                 enum bdi_stat_item item)
 127 {
 128         s64 sum;
 129         unsigned long flags;
 130
 131         local_irq_save(flags);
 132         sum = __bdi_stat_sum(bdi, item);
 133         local_irq_restore(flags);
 134
 135         return sum;
 136 }
 137
 138 extern void bdi_writeout_inc(struct backing_dev_info *bdi);
 139
 140 /*
 141  * maximal error of a stat counter.
 142  */
 143 static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
 144 {
 145 #ifdef CONFIG_SMP
 146         return nr_cpu_ids * BDI_STAT_BATCH;
 147 #else
 148         return 1;
 149 #endif
 150 }
 151
 152 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
 153 int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
 154
 155 /*
 156  * Flags in backing_dev_info::capability
 157  *
 158  * The first three flags control whether dirty pages will contribute to the
 159  * VM's accounting and whether writepages() should be called for dirty pages
 160  * (something that would not, for example, be appropriate for ramfs)
 161  *
 162  * WARNING: these flags are closely related and should not normally be
 163  * used separately.  The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
 164  * three flags into a single convenience macro.
 165  *
 166  * BDI_CAP_NO_ACCT_DIRTY:  Dirty pages shouldn't contribute to accounting
 167  * BDI_CAP_NO_WRITEBACK:   Don't write pages back
 168  * BDI_CAP_NO_ACCT_WB:     Don't automatically account writeback pages
 169  *
 170  * These flags let !MMU mmap() govern direct device mapping vs immediate
 171  * copying more easily for MAP_PRIVATE, especially for ROM filesystems.
 172  *
 173  * BDI_CAP_MAP_COPY:       Copy can be mapped (MAP_PRIVATE)
 174  * BDI_CAP_MAP_DIRECT:     Can be mapped directly (MAP_SHARED)
 175  * BDI_CAP_READ_MAP:       Can be mapped for reading
 176  * BDI_CAP_WRITE_MAP:      Can be mapped for writing
 177  * BDI_CAP_EXEC_MAP:       Can be mapped for execution
 178  *
 179  * BDI_CAP_SWAP_BACKED:    Count shmem/tmpfs objects as swap-backed.
 180  */
 181 #define BDI_CAP_NO_ACCT_DIRTY   0x00000001
 182 #define BDI_CAP_NO_WRITEBACK    0x00000002
 183 #define BDI_CAP_MAP_COPY        0x00000004
 184 #define BDI_CAP_MAP_DIRECT      0x00000008
 185 #define BDI_CAP_READ_MAP        0x00000010
 186 #define BDI_CAP_WRITE_MAP       0x00000020
 187 #define BDI_CAP_EXEC_MAP        0x00000040
 188 #define BDI_CAP_NO_ACCT_WB      0x00000080
 189 #define BDI_CAP_SWAP_BACKED     0x00000100
 190
 191 #define BDI_CAP_VMFLAGS \
 192         (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
 193
 194 #define BDI_CAP_NO_ACCT_AND_WRITEBACK \
 195         (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
 196
 197 #if defined(VM_MAYREAD) && \
 198         (BDI_CAP_READ_MAP != VM_MAYREAD || \
 199          BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
 200          BDI_CAP_EXEC_MAP != VM_MAYEXEC)
 201 #error please change backing_dev_info::capabilities flags
 202 #endif
 203
 204 extern struct backing_dev_info default_backing_dev_info;
 205 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
 206
 207 int writeback_in_progress(struct backing_dev_info *bdi);
 208
 209 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
 210 {
 211         if (bdi->congested_fn)
 212                 return bdi->congested_fn(bdi->congested_data, bdi_bits);
 213         return (bdi->state & bdi_bits);
 214 }
 215
 216 static inline int bdi_read_congested(struct backing_dev_info *bdi)
 217 {
 218         return bdi_congested(bdi, 1 << BDI_sync_congested);
 219 }
 220
 221 static inline int bdi_write_congested(struct backing_dev_info *bdi)
 222 {
 223         return bdi_congested(bdi, 1 << BDI_async_congested);
 224 }
 225
 226 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 227 {
 228         return bdi_congested(bdi, (1 << BDI_sync_congested) |
 229                                   (1 << BDI_async_congested));
 230 }
 231
 232 enum {
 233         BLK_RW_ASYNC    = 0,
 234         BLK_RW_SYNC     = 1,
 235 };
 236
 237 void clear_bdi_congested(struct backing_dev_info *bdi, int sync);
 238 void set_bdi_congested(struct backing_dev_info *bdi, int sync);
 239 long congestion_wait(int sync, long timeout);
 240
 241
 242 static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
 243 {
 244         return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
 245 }
 246
 247 static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
 248 {
 249         return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
 250 }
 251
 252 static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
 253 {
 254         /* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
 255         return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
 256                                       BDI_CAP_NO_WRITEBACK));
 257 }
 258
 259 static inline bool bdi_cap_swap_backed(struct backing_dev_info *bdi)
 260 {
 261         return bdi->capabilities & BDI_CAP_SWAP_BACKED;
 262 }
 263
 264 static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
 265 {
 266         return bdi_cap_writeback_dirty(mapping->backing_dev_info);
 267 }
 268
 269 static inline bool mapping_cap_account_dirty(struct address_space *mapping)
 270 {
 271         return bdi_cap_account_dirty(mapping->backing_dev_info);
 272 }
 273
 274 static inline bool mapping_cap_swap_backed(struct address_space *mapping)
 275 {
 276         return bdi_cap_swap_backed(mapping->backing_dev_info);
 277 }
 278
 279 #endif          /* _LINUX_BACKING_DEV_H */