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 struct page;
  14
  15 /*
  16  * Bits in backing_dev_info.state
  17  */
  18 enum bdi_state {
  19         BDI_pdflush,            /* A pdflush thread is working this device */
  20         BDI_write_congested,    /* The write queue is getting full */
  21         BDI_read_congested,     /* The read queue is getting full */
  22         BDI_unused,             /* Available bits start here */
  23 };
  24
  25 typedef int (congested_fn)(void *, int);
  26
  27 struct backing_dev_info {
  28         unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
  29         unsigned long state;    /* Always use atomic bitops on this */
  30         unsigned int capabilities; /* Device capabilities */
  31         congested_fn *congested_fn; /* Function pointer if device is md/dm */
  32         void *congested_data;   /* Pointer to aux data for congested func */
  33         void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
  34         void *unplug_io_data;
  35 };
  36
  37
  38 /*
  39  * Flags in backing_dev_info::capability
  40  * - The first two flags control whether dirty pages will contribute to the
  41  *   VM's accounting and whether writepages() should be called for dirty pages
  42  *   (something that would not, for example, be appropriate for ramfs)
  43  * - These flags let !MMU mmap() govern direct device mapping vs immediate
  44  *   copying more easily for MAP_PRIVATE, especially for ROM filesystems
  45  */
  46 #define BDI_CAP_NO_ACCT_DIRTY   0x00000001      /* Dirty pages shouldn't contribute to accounting */
  47 #define BDI_CAP_NO_WRITEBACK    0x00000002      /* Don't write pages back */
  48 #define BDI_CAP_MAP_COPY        0x00000004      /* Copy can be mapped (MAP_PRIVATE) */
  49 #define BDI_CAP_MAP_DIRECT      0x00000008      /* Can be mapped directly (MAP_SHARED) */
  50 #define BDI_CAP_READ_MAP        0x00000010      /* Can be mapped for reading */
  51 #define BDI_CAP_WRITE_MAP       0x00000020      /* Can be mapped for writing */
  52 #define BDI_CAP_EXEC_MAP        0x00000040      /* Can be mapped for execution */
  53 #define BDI_CAP_VMFLAGS \
  54         (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
  55
  56 #if defined(VM_MAYREAD) && \
  57         (BDI_CAP_READ_MAP != VM_MAYREAD || \
  58          BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
  59          BDI_CAP_EXEC_MAP != VM_MAYEXEC)
  60 #error please change backing_dev_info::capabilities flags
  61 #endif
  62
  63 extern struct backing_dev_info default_backing_dev_info;
  64 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
  65
  66 int writeback_acquire(struct backing_dev_info *bdi);
  67 int writeback_in_progress(struct backing_dev_info *bdi);
  68 void writeback_release(struct backing_dev_info *bdi);
  69
  70 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
  71 {
  72         if (bdi->congested_fn)
  73                 return bdi->congested_fn(bdi->congested_data, bdi_bits);
  74         return (bdi->state & bdi_bits);
  75 }
  76
  77 static inline int bdi_read_congested(struct backing_dev_info *bdi)
  78 {
  79         return bdi_congested(bdi, 1 << BDI_read_congested);
  80 }
  81
  82 static inline int bdi_write_congested(struct backing_dev_info *bdi)
  83 {
  84         return bdi_congested(bdi, 1 << BDI_write_congested);
  85 }
  86
  87 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
  88 {
  89         return bdi_congested(bdi, (1 << BDI_read_congested)|
  90                                   (1 << BDI_write_congested));
  91 }
  92
  93 void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
  94 void set_bdi_congested(struct backing_dev_info *bdi, int rw);
  95 long congestion_wait(int rw, long timeout);
  96 void congestion_end(int rw);
  97
  98 #define bdi_cap_writeback_dirty(bdi) \
  99         (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
 100
 101 #define bdi_cap_account_dirty(bdi) \
 102         (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
 103
 104 #define mapping_cap_writeback_dirty(mapping) \
 105         bdi_cap_writeback_dirty((mapping)->backing_dev_info)
 106
 107 #define mapping_cap_account_dirty(mapping) \
 108         bdi_cap_account_dirty((mapping)->backing_dev_info)
 109
 110
 111 #endif          /* _LINUX_BACKING_DEV_H */