#ifndef __MFS_BUF_H__

#define __MFS_BUF_H__

#include "clean.h"

/* Buffer (block) cache. To acquire a block, a routine calls get_block(),

* telling which block it wants. The block is then regarded as "in use"

* and has its 'b_count' field incremented. All the blocks that are not

* in use are chained together in an LRU list, with 'front' pointing

* to the least recently used block, and 'rear' to the most recently used

* block. A reverse chain, using the field b_prev is also maintained.

* Usage for LRU is measured by the time the put_block() is done. The second

* parameter to put_block() can violate the LRU order and put a block on the

* front of the list, if it will probably not be needed soon. If a block

* is modified, the modifying routine must set b_dirt to DIRTY, so the block

* will eventually be rewritten to the disk.

*/

#include <sys/dirent.h>

union fsdata_u {

char b__data[1]; /* ordinary user data */

/* directory block */

struct direct b__dir[1];

/* V2 indirect block */

zone_t b__v2_ind[1];

/* V2 inode block */

d2_inode b__v2_ino[1];

/* bit map block */

bitchunk_t b__bitmap[1];

};

/* A block is free if b_dev == NO_DEV. */

/* These defs make it possible to use to bp->b_data instead of bp->b.b__data */

#define b_data(b) ((union fsdata_u *) b->data)->b__data

#define b_dir(b) ((union fsdata_u *) b->data)->b__dir

#define b_v2_ind(b) ((union fsdata_u *) b->data)->b__v2_ind

#define b_v2_ino(b) ((union fsdata_u *) b->data)->b__v2_ino

#define b_bitmap(b) ((union fsdata_u *) b->data)->b__bitmap

#endif