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

[Andrew Doran <ad%netbsd.org@localhost>]

The following reply was made to PR kern/41189; it has been noted by GNATS.

From: Andrew Doran <ad%netbsd.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
        netbsd-bugs%netbsd.org@localhost, jdwhite%iastate.edu@localhost
Subject: Re: kern/41189: kernel panic xen dom0 using mke2fs & WAPBL
Date: Mon, 4 May 2009 23:05:08 +0000

 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