minix/servers/ext2/buf.h
Ben Gras 6c8f7fc3ba netbsd dirent.h, import sys/sys *.h, mfs cleanup
. add all sys/sys headers not already present to help compiling
	. take netbsd dirent.h and struct dirent; main result is
	  introducing d_type and d_namlen that have to be set by getdents()
	  in all FS code implementing it
	. d_off is gone
	. alignment of the struct has become 8 bytes instead of 4
	. remove _MAX_BLOCK_SIZE, _MIN_BLOCK_SIZE, _STATIC_BLOCK_SIZE
	. libminlib: cleanup unused yet duplicate code
	. mfs: throw out the long-broken v1, v2 support
	. new test for dirent contents filled by getdents()

Change-Id: I1459755c7ba5e5d1c9396d3a587ce6e63ddc283e
2014-03-01 09:04:59 +01:00

34 lines
1.3 KiB
C

/* 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.
*/
#ifndef EXT2_BUF_H
#define EXT2_BUF_H
#include <sys/dirent.h>
union fsdata_u {
char b__data[1]; /* ordinary user data */
/* indirect block */
block_t b__ind[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(bp) ((union fsdata_u *) bp->data)->b__data
#define b_ind(bp) ((union fsdata_u *) bp->data)->b__ind
#define b_bitmap(bp) ((union fsdata_u *) bp->data)->b__bitmap
#endif /* EXT2_BUF_H */