bd3cde4571
Add primary cache management feature to libminixfs as mfs and ext2
currently do separately, remove cache code from mfs and ext2, and make
them use the libminixfs interface. This makes all fields of the buf
struct private to libminixfs and FS clients aren't supposed to access
them at all. Only the opaque 'void *data' field (the FS block contents,
used to be called bp) is to be accessed by the FS client.
The main purpose is to implement the interface to the 2ndary vm cache
just once, get rid of some code duplication, and add a little
abstraction to reduce the code inertia of the whole caching business.
Some minor sanity checking and prohibition done by mfs in this code
as removed from the generic primary cache code as a result:
- checking all inodes are not in use when allocating/resizing
the cache
- checking readonly filesystems aren't written to
- checking the superblock isn't written to on mounted filesystems
The minixfslib code relies on fs_blockstats() in the client filesystem to
return some FS usage information.
34 lines
1.4 KiB
C
34 lines
1.4 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 <dirent.h>
|
|
|
|
union fsdata_u {
|
|
char b__data[_MAX_BLOCK_SIZE]; /* ordinary user data */
|
|
/* indirect block */
|
|
block_t b__ind[_MAX_BLOCK_SIZE/sizeof(block_t)];
|
|
/* bit map block */
|
|
bitchunk_t b__bitmap[FS_BITMAP_CHUNKS(_MAX_BLOCK_SIZE)];
|
|
};
|
|
|
|
/* 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 */
|