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         int memory_backed;      /* Cannot clean pages with writepage */
  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 extern struct backing_dev_info default_backing_dev_info;
  36 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
  37
  38 int writeback_acquire(struct backing_dev_info *bdi);
  39 int writeback_in_progress(struct backing_dev_info *bdi);
  40 void writeback_release(struct backing_dev_info *bdi);
  41
  42 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
  43 {
  44         if (bdi->congested_fn)
  45                 return bdi->congested_fn(bdi->congested_data, bdi_bits);
  46         return (bdi->state & bdi_bits);
  47 }
  48
  49 static inline int bdi_read_congested(struct backing_dev_info *bdi)
  50 {
  51         return bdi_congested(bdi, 1 << BDI_read_congested);
  52 }
  53
  54 static inline int bdi_write_congested(struct backing_dev_info *bdi)
  55 {
  56         return bdi_congested(bdi, 1 << BDI_write_congested);
  57 }
  58
  59 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
  60 {
  61         return bdi_congested(bdi, (1 << BDI_read_congested)|
  62                                   (1 << BDI_write_congested));
  63 }
  64
  65 #endif          /* _LINUX_BACKING_DEV_H */