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         BDI_RECLAIMABLE,
  31         BDI_WRITEBACK,
  32         NR_BDI_STAT_ITEMS
  33 };
  34
  35 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
  36
  37 struct backing_dev_info {
  38         unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
  39         unsigned long state;    /* Always use atomic bitops on this */
  40         unsigned int capabilities; /* Device capabilities */
  41         congested_fn *congested_fn; /* Function pointer if device is md/dm */
  42         void *congested_data;   /* Pointer to aux data for congested func */
  43         void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
  44         void *unplug_io_data;
  45
  46         struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
  47 };
  48
  49 int bdi_init(struct backing_dev_info *bdi);
  50 void bdi_destroy(struct backing_dev_info *bdi);
  51
  52 static inline void __add_bdi_stat(struct backing_dev_info *bdi,
  53                 enum bdi_stat_item item, s64 amount)
  54 {
  55         __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
  56 }
  57
  58 static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
  59                 enum bdi_stat_item item)
  60 {
  61         __add_bdi_stat(bdi, item, 1);
  62 }
  63
  64 static inline void inc_bdi_stat(struct backing_dev_info *bdi,
  65                 enum bdi_stat_item item)
  66 {
  67         unsigned long flags;
  68
  69         local_irq_save(flags);
  70         __inc_bdi_stat(bdi, item);
  71         local_irq_restore(flags);
  72 }
  73
  74 static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
  75                 enum bdi_stat_item item)
  76 {
  77         __add_bdi_stat(bdi, item, -1);
  78 }
  79
  80 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
  81                 enum bdi_stat_item item)
  82 {
  83         unsigned long flags;
  84
  85         local_irq_save(flags);
  86         __dec_bdi_stat(bdi, item);
  87         local_irq_restore(flags);
  88 }
  89
  90 static inline s64 bdi_stat(struct backing_dev_info *bdi,
  91                 enum bdi_stat_item item)
  92 {
  93         return percpu_counter_read_positive(&bdi->bdi_stat[item]);
  94 }
  95
  96 static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
  97                 enum bdi_stat_item item)
  98 {
  99         return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
 100 }
 101
 102 static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
 103                 enum bdi_stat_item item)
 104 {
 105         s64 sum;
 106         unsigned long flags;
 107
 108         local_irq_save(flags);
 109         sum = __bdi_stat_sum(bdi, item);
 110         local_irq_restore(flags);
 111
 112         return sum;
 113 }
 114
 115 /*
 116  * maximal error of a stat counter.
 117  */
 118 static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
 119 {
 120 #ifdef CONFIG_SMP
 121         return nr_cpu_ids * BDI_STAT_BATCH;
 122 #else
 123         return 1;
 124 #endif
 125 }
 126
 127 /*
 128  * Flags in backing_dev_info::capability
 129  * - The first two flags control whether dirty pages will contribute to the
 130  *   VM's accounting and whether writepages() should be called for dirty pages
 131  *   (something that would not, for example, be appropriate for ramfs)
 132  * - These flags let !MMU mmap() govern direct device mapping vs immediate
 133  *   copying more easily for MAP_PRIVATE, especially for ROM filesystems
 134  */
 135 #define BDI_CAP_NO_ACCT_DIRTY   0x00000001      /* Dirty pages shouldn't contribute to accounting */
 136 #define BDI_CAP_NO_WRITEBACK    0x00000002      /* Don't write pages back */
 137 #define BDI_CAP_MAP_COPY        0x00000004      /* Copy can be mapped (MAP_PRIVATE) */
 138 #define BDI_CAP_MAP_DIRECT      0x00000008      /* Can be mapped directly (MAP_SHARED) */
 139 #define BDI_CAP_READ_MAP        0x00000010      /* Can be mapped for reading */
 140 #define BDI_CAP_WRITE_MAP       0x00000020      /* Can be mapped for writing */
 141 #define BDI_CAP_EXEC_MAP        0x00000040      /* Can be mapped for execution */
 142 #define BDI_CAP_VMFLAGS \
 143         (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
 144
 145 #if defined(VM_MAYREAD) && \
 146         (BDI_CAP_READ_MAP != VM_MAYREAD || \
 147          BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
 148          BDI_CAP_EXEC_MAP != VM_MAYEXEC)
 149 #error please change backing_dev_info::capabilities flags
 150 #endif
 151
 152 extern struct backing_dev_info default_backing_dev_info;
 153 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
 154
 155 int writeback_acquire(struct backing_dev_info *bdi);
 156 int writeback_in_progress(struct backing_dev_info *bdi);
 157 void writeback_release(struct backing_dev_info *bdi);
 158
 159 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
 160 {
 161         if (bdi->congested_fn)
 162                 return bdi->congested_fn(bdi->congested_data, bdi_bits);
 163         return (bdi->state & bdi_bits);
 164 }
 165
 166 static inline int bdi_read_congested(struct backing_dev_info *bdi)
 167 {
 168         return bdi_congested(bdi, 1 << BDI_read_congested);
 169 }
 170
 171 static inline int bdi_write_congested(struct backing_dev_info *bdi)
 172 {
 173         return bdi_congested(bdi, 1 << BDI_write_congested);
 174 }
 175
 176 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 177 {
 178         return bdi_congested(bdi, (1 << BDI_read_congested)|
 179                                   (1 << BDI_write_congested));
 180 }
 181
 182 void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
 183 void set_bdi_congested(struct backing_dev_info *bdi, int rw);
 184 long congestion_wait(int rw, long timeout);
 185
 186 #define bdi_cap_writeback_dirty(bdi) \
 187         (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
 188
 189 #define bdi_cap_account_dirty(bdi) \
 190         (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
 191
 192 #define mapping_cap_writeback_dirty(mapping) \
 193         bdi_cap_writeback_dirty((mapping)->backing_dev_info)
 194
 195 #define mapping_cap_account_dirty(mapping) \
 196         bdi_cap_account_dirty((mapping)->backing_dev_info)
 197
 198
 199 #endif          /* _LINUX_BACKING_DEV_H */