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Re: kern/41189: kernel panic xen dom0 using mke2fs & WAPBL

On Sun, Apr 26, 2009 at 05:05:02AM +0000, David Holland wrote:

>  Realistically devfs won't change the real problem (confusing whether
>  um_devvp belongs to the fs mounted on it or the fs it sits on) but
>  just replace wapbl-related issues with comparable devfs-related
>  issues.
>  The real fix is to change the buffer cache indexing scheme. Right now
>  the buffer cache is indexed by vnode and offset; it should be indexed
>  by filesystem (that is, struct mount), vnode or inode number, and
>  offset. This should use a reserved inode number or vnode pointer for
>  whole-fs buffers; and whole-fs buffers should be getting queued in the
>  mount structure, not any vnode.
>  Then at the cost of what should be only a small amount of new code
>  (but a lot of interface changes) the potential for confusion will go
>  away permanently, and we can change the name of um_devvp so as to hunt
>  down and kill all further misuses of it.

I disagree. I think the solution is:

- devfs
- kill block devices in userspace
- allow unaligned I/O to disk devices via the raw node

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