Re: [TUHS] VFS prior to 1984

[Larry McVoy <lm@mcvoy.com>]

On Mon, Jun 29, 2020 at 04:53:50PM +0200, Paul Ruizendaal wrote:
> 
> > On 29 Jun 2020, at 16:45, Larry McVoy <lm@mcvoy.com> wrote:
> > 
> > On Mon, Jun 29, 2020 at 11:11:17AM +0200, Paul Ruizendaal wrote:
> >> As several people have observed in this topic, indeed there appears to be a close relationship between a device switch and a file system switch.
> > 
> > Yep.  If you think in objects, they are both objects with a set of methods.
> > Pretty much two instances of the same idea.
> 
> Phrased that way all OO programs have a close relationship between them. Maybe: "they are both rather similar objects with a rather similar set of methods"?

They are two different classes, similar, but not the same.  It's really
4 classes, vfs, vnode for FS and block/char for devices.  This is from
SunOS 4.1.1 that I happened to have an install image sitting around.
Took me forever to find the device definitions, I resorted to

find . -type f -name '*.h' -print | xargs grep strategy

It's in include/sys/conf.h because, well, that's obvious, right?

struct vfsops {
        int     (*vfs_mount)();         /* mount file system */
        int     (*vfs_unmount)();       /* unmount file system */
        int     (*vfs_root)();          /* get root vnode */
        int     (*vfs_statfs)();        /* get fs statistics */
        int     (*vfs_sync)();          /* flush fs buffers */
        int     (*vfs_vget)();          /* get vnode from fid */
        int     (*vfs_mountroot)();     /* mount the root filesystem */
        int     (*vfs_swapvp)();        /* return vnode for swap */
};

struct vnodeops {
        int     (*vn_open)();
        int     (*vn_close)();
        int     (*vn_rdwr)();
        int     (*vn_ioctl)();
        int     (*vn_select)();
        int     (*vn_getattr)();
        int     (*vn_setattr)();
        int     (*vn_access)();
        int     (*vn_lookup)();
        int     (*vn_create)();
        int     (*vn_remove)();
        int     (*vn_link)();
        int     (*vn_rename)();
        int     (*vn_mkdir)();
        int     (*vn_rmdir)();
        int     (*vn_readdir)();
        int     (*vn_symlink)();
        int     (*vn_readlink)();
        int     (*vn_fsync)();
        int     (*vn_inactive)();
        int     (*vn_lockctl)();
        int     (*vn_fid)();
        int     (*vn_getpage)();
        int     (*vn_putpage)();
        int     (*vn_map)();
        int     (*vn_dump)();
        int     (*vn_cmp)();
        int     (*vn_realvp)();
        int     (*vn_cntl)();
};

/* two different device classes, block and char */
struct bdevsw {
        int     (*d_open)();
        int     (*d_close)();
        int     (*d_strategy)();
        int     (*d_dump)();
        int     (*d_psize)();
        int     d_flags;
};

struct cdevsw {
        int     (*d_open)();
        int     (*d_close)();
        int     (*d_read)();
        int     (*d_write)();
        int     (*d_ioctl)();
        int     (*d_reset)();
        int     (*d_select)();
        int     (*d_mmap)();
        struct  streamtab *d_str;
        int     (*d_segmap)();
};

-- 
---
Larry McVoy            	     lm at mcvoy.com             http://www.mcvoy.com/lm