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 <asm/atomic.h>
  14
  15 struct page;
  16
  17 /*
  18  * Bits in backing_dev_info.state
  19  */
  20 enum bdi_state {
  21         BDI_pdflush,            /* A pdflush thread is working this device */
  22         BDI_write_congested,    /* The write queue is getting full */
  23         BDI_read_congested,     /* The read queue is getting full */
  24         BDI_unused,             /* Available bits start here */
  25 };
  26
  27 typedef int (congested_fn)(void *, int);
  28
  29 enum bdi_stat_item {
  30         NR_BDI_STAT_ITEMS
  31 };
  32
  33 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
  34
  35 struct backing_dev_info {
  36         unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
  37         unsigned long state;    /* Always use atomic bitops on this */
  38         unsigned int capabilities; /* Device capabilities */
  39         congested_fn *congested_fn; /* Function pointer if device is md/dm */
  40         void *congested_data;   /* Pointer to aux data for congested func */
  41         void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
  42         void *unplug_io_data;
  43
  44         struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
  45 };
  46
  47 int bdi_init(struct backing_dev_info *bdi);
  48 void bdi_destroy(struct backing_dev_info *bdi);
  49
  50 static inline void __add_bdi_stat(struct backing_dev_info *bdi,
  51                 enum bdi_stat_item item, s64 amount)
  52 {
  53         __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
  54 }
  55
  56 static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
  57                 enum bdi_stat_item item)
  58 {
  59         __add_bdi_stat(bdi, item, 1);
  60 }
  61
  62 static inline void inc_bdi_stat(struct backing_dev_info *bdi,
  63                 enum bdi_stat_item item)
  64 {
  65         unsigned long flags;
  66
  67         local_irq_save(flags);
  68         __inc_bdi_stat(bdi, item);
  69         local_irq_restore(flags);
  70 }
  71
  72 static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
  73                 enum bdi_stat_item item)
  74 {
  75         __add_bdi_stat(bdi, item, -1);
  76 }
  77
  78 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
  79                 enum bdi_stat_item item)
  80 {
  81         unsigned long flags;
  82
  83         local_irq_save(flags);
  84         __dec_bdi_stat(bdi, item);
  85         local_irq_restore(flags);
  86 }
  87
  88 static inline s64 bdi_stat(struct backing_dev_info *bdi,
  89                 enum bdi_stat_item item)
  90 {
  91         return percpu_counter_read_positive(&bdi->bdi_stat[item]);
  92 }
  93
  94 static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
  95                 enum bdi_stat_item item)
  96 {
  97         return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
  98 }
  99
 100 static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
 101                 enum bdi_stat_item item)
 102 {
 103         s64 sum;
 104         unsigned long flags;
 105
 106         local_irq_save(flags);
 107         sum = __bdi_stat_sum(bdi, item);
 108         local_irq_restore(flags);
 109
 110         return sum;
 111 }
 112
 113 /*
 114  * maximal error of a stat counter.
 115  */
 116 static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
 117 {
 118 #ifdef CONFIG_SMP
 119         return nr_cpu_ids * BDI_STAT_BATCH;
 120 #else
 121         return 1;
 122 #endif
 123 }
 124
 125 /*
 126  * Flags in backing_dev_info::capability
 127  * - The first two flags control whether dirty pages will contribute to the
 128  *   VM's accounting and whether writepages() should be called for dirty pages
 129  *   (something that would not, for example, be appropriate for ramfs)
 130  * - These flags let !MMU mmap() govern direct device mapping vs immediate
 131  *   copying more easily for MAP_PRIVATE, especially for ROM filesystems
 132  */
 133 #define BDI_CAP_NO_ACCT_DIRTY   0x00000001      /* Dirty pages shouldn't contribute to accounting */
 134 #define BDI_CAP_NO_WRITEBACK    0x00000002      /* Don't write pages back */
 135 #define BDI_CAP_MAP_COPY        0x00000004      /* Copy can be mapped (MAP_PRIVATE) */
 136 #define BDI_CAP_MAP_DIRECT      0x00000008      /* Can be mapped directly (MAP_SHARED) */
 137 #define BDI_CAP_READ_MAP        0x00000010      /* Can be mapped for reading */
 138 #define BDI_CAP_WRITE_MAP       0x00000020      /* Can be mapped for writing */
 139 #define BDI_CAP_EXEC_MAP        0x00000040      /* Can be mapped for execution */
 140 #define BDI_CAP_VMFLAGS \
 141         (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
 142
 143 #if defined(VM_MAYREAD) && \
 144         (BDI_CAP_READ_MAP != VM_MAYREAD || \
 145          BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
 146          BDI_CAP_EXEC_MAP != VM_MAYEXEC)
 147 #error please change backing_dev_info::capabilities flags
 148 #endif
 149
 150 extern struct backing_dev_info default_backing_dev_info;
 151 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
 152
 153 int writeback_acquire(struct backing_dev_info *bdi);
 154 int writeback_in_progress(struct backing_dev_info *bdi);
 155 void writeback_release(struct backing_dev_info *bdi);
 156
 157 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
 158 {
 159         if (bdi->congested_fn)
 160                 return bdi->congested_fn(bdi->congested_data, bdi_bits);
 161         return (bdi->state & bdi_bits);
 162 }
 163
 164 static inline int bdi_read_congested(struct backing_dev_info *bdi)
 165 {
 166         return bdi_congested(bdi, 1 << BDI_read_congested);
 167 }
 168
 169 static inline int bdi_write_congested(struct backing_dev_info *bdi)
 170 {
 171         return bdi_congested(bdi, 1 << BDI_write_congested);
 172 }
 173
 174 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 175 {
 176         return bdi_congested(bdi, (1 << BDI_read_congested)|
 177                                   (1 << BDI_write_congested));
 178 }
 179
 180 void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
 181 void set_bdi_congested(struct backing_dev_info *bdi, int rw);
 182 long congestion_wait(int rw, long timeout);
 183
 184 #define bdi_cap_writeback_dirty(bdi) \
 185         (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
 186
 187 #define bdi_cap_account_dirty(bdi) \
 188         (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
 189
 190 #define mapping_cap_writeback_dirty(mapping) \
 191         bdi_cap_writeback_dirty((mapping)->backing_dev_info)
 192
 193 #define mapping_cap_account_dirty(mapping) \
 194         bdi_cap_account_dirty((mapping)->backing_dev_info)
 195
 196
 197 #endif          /* _LINUX_BACKING_DEV_H */