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 <asm/atomic.h>
  12
  13 /*
  14  * Bits in backing_dev_info.state
  15  */
  16 enum bdi_state {
  17         BDI_pdflush,            /* A pdflush thread is working this device */
  18         BDI_write_congested,    /* The write queue is getting full */
  19         BDI_read_congested,     /* The read queue is getting full */
  20         BDI_unused,             /* Available bits start here */
  21 };
  22
  23 typedef int (congested_fn)(void *, int);
  24
  25 struct backing_dev_info {
  26         unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
  27         unsigned long state;    /* Always use atomic bitops on this */
  28         unsigned int capabilities; /* Device capabilities */
  29         congested_fn *congested_fn; /* Function pointer if device is md/dm */
  30         void *congested_data;   /* Pointer to aux data for congested func */
  31         void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
  32         void *unplug_io_data;
  33 };
  34
  35
  36 /*
  37  * Flags in backing_dev_info::capability
  38  * - The first two flags control whether dirty pages will contribute to the
  39  *   VM's accounting and whether writepages() should be called for dirty pages
  40  *   (something that would not, for example, be appropriate for ramfs)
  41  * - These flags let !MMU mmap() govern direct device mapping vs immediate
  42  *   copying more easily for MAP_PRIVATE, especially for ROM filesystems
  43  */
  44 #define BDI_CAP_NO_ACCT_DIRTY   0x00000001      /* Dirty pages shouldn't contribute to accounting */
  45 #define BDI_CAP_NO_WRITEBACK    0x00000002      /* Don't write pages back */
  46 #define BDI_CAP_MAP_COPY        0x00000004      /* Copy can be mapped (MAP_PRIVATE) */
  47 #define BDI_CAP_MAP_DIRECT      0x00000008      /* Can be mapped directly (MAP_SHARED) */
  48 #define BDI_CAP_READ_MAP        0x00000010      /* Can be mapped for reading */
  49 #define BDI_CAP_WRITE_MAP       0x00000020      /* Can be mapped for writing */
  50 #define BDI_CAP_EXEC_MAP        0x00000040      /* Can be mapped for execution */
  51 #define BDI_CAP_VMFLAGS \
  52         (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
  53
  54 #if defined(VM_MAYREAD) && \
  55         (BDI_CAP_READ_MAP != VM_MAYREAD || \
  56          BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
  57          BDI_CAP_EXEC_MAP != VM_MAYEXEC)
  58 #error please change backing_dev_info::capabilities flags
  59 #endif
  60
  61 extern struct backing_dev_info default_backing_dev_info;
  62 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
  63
  64 int writeback_acquire(struct backing_dev_info *bdi);
  65 int writeback_in_progress(struct backing_dev_info *bdi);
  66 void writeback_release(struct backing_dev_info *bdi);
  67
  68 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
  69 {
  70         if (bdi->congested_fn)
  71                 return bdi->congested_fn(bdi->congested_data, bdi_bits);
  72         return (bdi->state & bdi_bits);
  73 }
  74
  75 static inline int bdi_read_congested(struct backing_dev_info *bdi)
  76 {
  77         return bdi_congested(bdi, 1 << BDI_read_congested);
  78 }
  79
  80 static inline int bdi_write_congested(struct backing_dev_info *bdi)
  81 {
  82         return bdi_congested(bdi, 1 << BDI_write_congested);
  83 }
  84
  85 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
  86 {
  87         return bdi_congested(bdi, (1 << BDI_read_congested)|
  88                                   (1 << BDI_write_congested));
  89 }
  90
  91 #define bdi_cap_writeback_dirty(bdi) \
  92         (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
  93
  94 #define bdi_cap_account_dirty(bdi) \
  95         (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
  96
  97 #define mapping_cap_writeback_dirty(mapping) \
  98         bdi_cap_writeback_dirty((mapping)->backing_dev_info)
  99
 100 #define mapping_cap_account_dirty(mapping) \
 101         bdi_cap_account_dirty((mapping)->backing_dev_info)
 102
 103
 104 #endif          /* _LINUX_BACKING_DEV_H */