LXR linux/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 */
  16enum 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
  23typedef int (congested_fn)(void *, int);
  24
  25struct 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
  35extern struct backing_dev_info default_backing_dev_info;
  36void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
  37
  38int writeback_acquire(struct backing_dev_info *bdi);
  39int writeback_in_progress(struct backing_dev_info *bdi);
  40void writeback_release(struct backing_dev_info *bdi);
  41
  42static 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
  49static inline int bdi_read_congested(struct backing_dev_info *bdi)
  50{
  51        return bdi_congested(bdi, 1 << BDI_read_congested);
  52}
  53
  54static inline int bdi_write_congested(struct backing_dev_info *bdi)
  55{
  56        return bdi_congested(bdi, 1 << BDI_write_congested);
  57}
  58
  59static 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 */
  66