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 <asm/atomic.h>
  15
  16 struct page;
  17
  18 /*
  19  * Bits in backing_dev_info.state
  20  */
  21 enum bdi_state {
  22         BDI_pdflush,            /* A pdflush thread is working this device */
  23         BDI_write_congested,    /* The write queue is getting full */
  24         BDI_read_congested,     /* The read queue is getting full */
  25         BDI_unused,             /* Available bits start here */
  26 };
  27
  28 typedef int (congested_fn)(void *, int);
  29
  30 enum bdi_stat_item {
  31         BDI_RECLAIMABLE,
  32         BDI_WRITEBACK,
  33         NR_BDI_STAT_ITEMS
  34 };
  35
  36 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
  37
  38 struct backing_dev_info {
  39         unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
  40         unsigned long state;    /* Always use atomic bitops on this */
  41         unsigned int capabilities; /* Device capabilities */
  42         congested_fn *congested_fn; /* Function pointer if device is md/dm */
  43         void *congested_data;   /* Pointer to aux data for congested func */
  44         void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
  45         void *unplug_io_data;
  46
  47         struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
  48
  49         struct prop_local_percpu completions;
  50         int dirty_exceeded;
  51 };
  52
  53 int bdi_init(struct backing_dev_info *bdi);
  54 void bdi_destroy(struct backing_dev_info *bdi);
  55
  56 static inline void __add_bdi_stat(struct backing_dev_info *bdi,
  57                 enum bdi_stat_item item, s64 amount)
  58 {
  59         __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
  60 }
  61
  62 static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
  63                 enum bdi_stat_item item)
  64 {
  65         __add_bdi_stat(bdi, item, 1);
  66 }
  67
  68 static inline void inc_bdi_stat(struct backing_dev_info *bdi,
  69                 enum bdi_stat_item item)
  70 {
  71         unsigned long flags;
  72
  73         local_irq_save(flags);
  74         __inc_bdi_stat(bdi, item);
  75         local_irq_restore(flags);
  76 }
  77
  78 static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
  79                 enum bdi_stat_item item)
  80 {
  81         __add_bdi_stat(bdi, item, -1);
  82 }
  83
  84 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
  85                 enum bdi_stat_item item)
  86 {
  87         unsigned long flags;
  88
  89         local_irq_save(flags);
  90         __dec_bdi_stat(bdi, item);
  91         local_irq_restore(flags);
  92 }
  93
  94 static inline s64 bdi_stat(struct backing_dev_info *bdi,
  95                 enum bdi_stat_item item)
  96 {
  97         return percpu_counter_read_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         return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
 104 }
 105
 106 static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
 107                 enum bdi_stat_item item)
 108 {
 109         s64 sum;
 110         unsigned long flags;
 111
 112         local_irq_save(flags);
 113         sum = __bdi_stat_sum(bdi, item);
 114         local_irq_restore(flags);
 115
 116         return sum;
 117 }
 118
 119 /*
 120  * maximal error of a stat counter.
 121  */
 122 static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
 123 {
 124 #ifdef CONFIG_SMP
 125         return nr_cpu_ids * BDI_STAT_BATCH;
 126 #else
 127         return 1;
 128 #endif
 129 }
 130
 131 /*
 132  * Flags in backing_dev_info::capability
 133  * - The first two flags control whether dirty pages will contribute to the
 134  *   VM's accounting and whether writepages() should be called for dirty pages
 135  *   (something that would not, for example, be appropriate for ramfs)
 136  * - These flags let !MMU mmap() govern direct device mapping vs immediate
 137  *   copying more easily for MAP_PRIVATE, especially for ROM filesystems
 138  */
 139 #define BDI_CAP_NO_ACCT_DIRTY   0x00000001      /* Dirty pages shouldn't contribute to accounting */
 140 #define BDI_CAP_NO_WRITEBACK    0x00000002      /* Don't write pages back */
 141 #define BDI_CAP_MAP_COPY        0x00000004      /* Copy can be mapped (MAP_PRIVATE) */
 142 #define BDI_CAP_MAP_DIRECT      0x00000008      /* Can be mapped directly (MAP_SHARED) */
 143 #define BDI_CAP_READ_MAP        0x00000010      /* Can be mapped for reading */
 144 #define BDI_CAP_WRITE_MAP       0x00000020      /* Can be mapped for writing */
 145 #define BDI_CAP_EXEC_MAP        0x00000040      /* Can be mapped for execution */
 146 #define BDI_CAP_VMFLAGS \
 147         (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
 148
 149 #if defined(VM_MAYREAD) && \
 150         (BDI_CAP_READ_MAP != VM_MAYREAD || \
 151          BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
 152          BDI_CAP_EXEC_MAP != VM_MAYEXEC)
 153 #error please change backing_dev_info::capabilities flags
 154 #endif
 155
 156 extern struct backing_dev_info default_backing_dev_info;
 157 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
 158
 159 int writeback_acquire(struct backing_dev_info *bdi);
 160 int writeback_in_progress(struct backing_dev_info *bdi);
 161 void writeback_release(struct backing_dev_info *bdi);
 162
 163 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
 164 {
 165         if (bdi->congested_fn)
 166                 return bdi->congested_fn(bdi->congested_data, bdi_bits);
 167         return (bdi->state & bdi_bits);
 168 }
 169
 170 static inline int bdi_read_congested(struct backing_dev_info *bdi)
 171 {
 172         return bdi_congested(bdi, 1 << BDI_read_congested);
 173 }
 174
 175 static inline int bdi_write_congested(struct backing_dev_info *bdi)
 176 {
 177         return bdi_congested(bdi, 1 << BDI_write_congested);
 178 }
 179
 180 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 181 {
 182         return bdi_congested(bdi, (1 << BDI_read_congested)|
 183                                   (1 << BDI_write_congested));
 184 }
 185
 186 void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
 187 void set_bdi_congested(struct backing_dev_info *bdi, int rw);
 188 long congestion_wait(int rw, long timeout);
 189
 190 #define bdi_cap_writeback_dirty(bdi) \
 191         (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
 192
 193 #define bdi_cap_account_dirty(bdi) \
 194         (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
 195
 196 #define mapping_cap_writeback_dirty(mapping) \
 197         bdi_cap_writeback_dirty((mapping)->backing_dev_info)
 198
 199 #define mapping_cap_account_dirty(mapping) \
 200         bdi_cap_account_dirty((mapping)->backing_dev_info)
 201
 202
 203 #endif          /* _LINUX_BACKING_DEV_H */