toaruos/docs/newvfs.md

New VFS Design Documentation

For reference: virtual functions in the old VFS

typedef uint32_t (*read_type_t) (struct fs_node *, uint32_t, uint32_t, uint8_t *);
typedef uint32_t (*write_type_t) (struct fs_node *, uint32_t, uint32_t, uint8_t *);
typedef void (*open_type_t) (struct fs_node *, unsigned int flags);
typedef void (*close_type_t) (struct fs_node *);
typedef struct dirent *(*readdir_type_t) (struct fs_node *, uint32_t);
typedef struct fs_node *(*finddir_type_t) (struct fs_node *, char *name);
typedef void (*create_type_t) (struct fs_node *, char *name, uint16_t permission);
typedef void (*unlink_type_t) (struct fs_node *, char *name);
typedef void (*mkdir_type_t) (struct fs_node *, char *name, uint16_t permission);
typedef int (*ioctl_type_t) (struct fs_node *, int request, void * argp);
typedef int (*get_size_type_t) (struct fs_node *);
typedef int (*chmod_type_t) (struct fs_node *, int mode);

Design Goals of the New VFS

1. Large file support from the beginning

   All 64-bit offsets and sizes.

2. Cached virtual file objects

   We currently have "objects that happen to exist from a malloc" and "objects we created from an open() call"...

3. Reference counting so we can actually close files

   Specifically, so we can close everything on exit.

4. Unix pipes

   The focus of this rewrite is supporting closing of pipes...

5. Permissions

   The current VFS can... uh... store them, but doesn't actually respect them.

6. Support for symbolic links

   Yeah.

7. Ground-up support for polling / file events.

   Sleep on multiple, etc.