minix/fs/pfs/buf.h

   1 #ifndef __PFS_BUF_H__
   2 #define __PFS_BUF_H__
   3
   4 /* Buffer (block) cache.
   5  */
   6
   7 struct buf {
   8   /* Data portion of the buffer. */
   9   char b_data[PIPE_BUF];     /* ordinary user data */
  10
  11   /* Header portion of the buffer. */
  12   struct buf *b_next;           /* used to link all free bufs in a chain */
  13   struct buf *b_prev;           /* used to link all free bufs the other way */
  14   ino_t b_num;                  /* inode number on minor device */
  15   dev_t b_dev;                  /* major | minor device where block resides */
  16   int b_bytes;                  /* Number of bytes allocated in bp */
  17   int b_count;                  /* Number of users of this buffer */
  18 };
  19
  20 /* A block is free if b_dev == NO_DEV. */
  21
  22
  23 EXTERN struct buf *front;       /* points to least recently used free block */
  24 EXTERN struct buf *rear;        /* points to most recently used free block */
  25
  26 #endif