| 139,6 → 139,8 |
|---|
| uint32_t size; |
| } __attribute__ ((packed)) fat_dentry_t; |
| |
| typedef uint16_t fat_cluster_t; |
| |
| typedef enum { |
| FAT_INVALID, |
| FAT_DIRECTORY, |
| 145,16 → 147,59 |
|---|
| FAT_FILE |
| } fat_node_type_t; |
| |
| struct fat_node; |
| |
| /** FAT index structure. |
| * |
| * This structure exists to help us to overcome certain limitations of the FAT |
| * file system design. The problem with FAT is that it is hard to find |
| * an entity which could represent a VFS index. There are two candidates: |
| * |
| * a) number of the node's first cluster |
| * b) the pair of the parent directory's first cluster and the dentry index |
| * within the parent directory |
| * |
| * We need VFS indices to be: |
| * A) unique |
| * B) stable in time, at least until the next mount |
| * |
| * Unfortunately a) does not meet the A) criterion because zero-length files |
| * will have the first cluster field cleared. And b) does not meet the B) |
| * criterion because unlink() and rename() will both free up the original |
| * dentry, which contains all the essential info about the file. |
| * |
| * Therefore, a completely opaque indices are used and the FAT server maintains |
| * a mapping between them and otherwise nice b) variant. On rename(), the VFS |
| * index stays unaltered, while the internal FAT "physical tree address" |
| * changes. The unlink case is also handled this way thanks to an in-core node |
| * pointer embedded in the index structure. |
| */ |
| typedef struct { |
| dev_handle_t dev_handle; |
| fs_index_t index; |
| /** |
| * Parent first cluster. |
| * Zero is used if this node is not linked, in which case nodep must |
| * contain a pointer to the in-core node structure. |
| * One is used when the parent is the root directory. |
| */ |
| fat_cluster_t pfc; |
| /** Parent directory entry index. */ |
| unsigned pdi; |
| /** Pointer to in-core node instance. */ |
| struct fat_node *nodep; |
| } fat_idx_t; |
| |
| /** FAT in-core node. */ |
| typedef struct { |
| /** Protects an instance of this type. */ |
| futex_t lock; |
| typedef struct fat_node { |
| fat_node_type_t type; |
| /** VFS index is the node's first allocated cluster. */ |
| fs_index_t index; |
| /** VFS index of the parent node. */ |
| fs_index_t pindex; |
| dev_handle_t dev_handle; |
| fat_idx_t *idx; |
| /** |
| * Node's first cluster. |
| * Zero is used for zero-length nodes. |
| * One is used to mark root directory. |
| */ |
| fat_cluster_t firstc; |
| /** FAT in-core node hash table link. */ |
| link_t fin_link; |
| /** FAT in-core node free list link. */ |