servers/pfs/buf.h

   1 /* Buffer (block) cache.
   2  */
   3
   4 struct buf {
   5   /* Data portion of the buffer. */
   6   char b_data[PIPE_BUF];     /* ordinary user data */
   7
   8   /* Header portion of the buffer. */
   9   struct buf *b_next;           /* used to link all free bufs in a chain */
  10   struct buf *b_prev;           /* used to link all free bufs the other way */
  11   ino_t b_num;                  /* inode number on minor device */
  12   dev_t b_dev;                  /* major | minor device where block resides */
  13   int b_bytes;                  /* Number of bytes allocated in bp */
  14   int b_count;                  /* Number of users of this buffer */
  15 };
  16
  17 /* A block is free if b_dev == NO_DEV. */
  18
  19 #define NIL_BUF ((struct buf *) 0)      /* indicates absence of a buffer */
  20
  21 #define BUFHASH(b) ((b) % NR_BUFS)
  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 EXTERN int bufs_in_use;         /* # bufs currently in use (not on free list)*/
  26