LXR linux/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
  18struct page;
  19struct device;
  20struct dentry;
  21
  22/*
  23 * Bits in backing_dev_info.state
  24 */
  25enum 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
  32typedef int (congested_fn)(void *, int);
  33
  34enum 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
  42struct 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
  67int bdi_init(struct backing_dev_info *bdi);
  68void bdi_destroy(struct backing_dev_info *bdi);
  69
  70int bdi_register(struct backing_dev_info *bdi, struct device *parent,
  71                const char *fmt, ...);
  72int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
  73void bdi_unregister(struct backing_dev_info *bdi);
  74
  75static 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
  81static 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
  87static 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
  97static 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
 103static 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
 113static 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
 119static 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
 125static 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
 138extern void bdi_writeout_inc(struct backing_dev_info *bdi);
 139
 140/*
 141 * maximal error of a stat counter.
 142 */
 143static 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
 152int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
 153int 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
 204extern struct backing_dev_info default_backing_dev_info;
 205void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
 206
 207int writeback_in_progress(struct backing_dev_info *bdi);
 208
 209static 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
 216static inline int bdi_read_congested(struct backing_dev_info *bdi)
 217{
 218        return bdi_congested(bdi, 1 << BDI_sync_congested);
 219}
 220
 221static inline int bdi_write_congested(struct backing_dev_info *bdi)
 222{
 223        return bdi_congested(bdi, 1 << BDI_async_congested);
 224}
 225
 226static 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
 232enum {
 233        BLK_RW_ASYNC    = 0,
 234        BLK_RW_SYNC     = 1,
 235};
 236
 237void clear_bdi_congested(struct backing_dev_info *bdi, int sync);
 238void set_bdi_congested(struct backing_dev_info *bdi, int sync);
 239long congestion_wait(int sync, long timeout);
 240
 241
 242static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
 243{
 244        return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
 245}
 246
 247static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
 248{
 249        return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
 250}
 251
 252static 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
 259static inline bool bdi_cap_swap_backed(struct backing_dev_info *bdi)
 260{
 261        return bdi->capabilities & BDI_CAP_SWAP_BACKED;
 262}
 263
 264static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
 265{
 266        return bdi_cap_writeback_dirty(mapping->backing_dev_info);
 267}
 268
 269static inline bool mapping_cap_account_dirty(struct address_space *mapping)
 270{
 271        return bdi_cap_account_dirty(mapping->backing_dev_info);
 272}
 273
 274static 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 */
 280