cache: update the metadata cache design

- instead of get_cache_block() returning a descriptor, have
  get_cache() returning const void *.
- have a subfunction to allow getting a block without reading it
  from disk, and returning the cache descriptor.  This will be
  used in ext2 to pre-seed block 0 with all zero.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

2 files changed, 11 insertions, 12 deletions

diff --git a/core/include/cache.h b/core/include/cache.h
index 7518bc84..0cf399af 100644
--- a/core/include/cache.h
+++ b/core/include/cache.h
@@ -6,20 +6,17 @@
 #include "disk.h"
 #include "fs.h"
 
-#define MAX_CACHE_ENTRIES  0x10 /* I find even this is enough:) */
-
 /* The cache structure */
-struct cache_struct {
-        block_t block;
-        struct cache_struct *prev;
-        struct cache_struct *next;
-        void  *data;
+struct cache {
+    block_t block;
+    struct cache *prev;
+    struct cache *next;
+    void *data;
 };
 
-
 /* functions defined in cache.c */
 void cache_init(struct device *, int);
-struct cache_struct* get_cache_block(struct device *, block_t);
-void print_cache(struct device *);
+const void *get_cache(struct device *, block_t);
+struct cache *_get_cache_block(struct device *, block_t);
 
 #endif /* cache.h */
diff --git a/core/include/fs.h b/core/include/fs.h
index cc9d21c4..8a173d9f 100644
--- a/core/include/fs.h
+++ b/core/include/fs.h
@@ -119,12 +119,14 @@ enum dev_type {CHS, EDD};
  *     the pointer points to the disk structure,
  *     the cache stuff.
  */
+struct cache;
+
 struct device {
     struct disk *disk;
 
     /* the cache stuff */
-    char* cache_data;
-    void* cache_head;
+    char *cache_data;
+    struct cache *cache_head;
     uint16_t cache_block_size;
     uint16_t cache_entries;
     uint32_t cache_size;