Respawn crashed PUFFS filesystems?

[manu%netbsd.org@localhost (Emmanuel Dreyfus)]

One of the benefits of userland filesystems is that a bug in a
filesystem will just crash the filesystem, not the whole kernel. But a
crashed filesystem causes an unmount, and leaves the system non fully
functionnal.

I thought that we could respawn a crashed userland filesystem, lookup
all active vnodes again, and redo all operations failed at crash time.
That way a crashed filesystem would  just cause a delay in ongoing
operations, but it would not even cause a failure. Does it makes sense?

One of the problem is to choose the command needed to respawn a
filesystem. A simple solution is to attempt /sbin/mount target for PUFFS
filesystems. Of course the feature would be broken in some cases, but we
could make the thing optional using a vfs.puffs.respawn sysctl, which
would contain a colon-separated mount points subjected to respawn.

The plan is very vague at that stage, ut I would like to know if it has
any merit before proceeding further.

-- 
Emmanuel Dreyfus
http://hcpnet.free.fr/pubz
manu%netbsd.org@localhost