Re: Another force unmount failure

[David Holland <dholland-tech%netbsd.org@localhost>]

On Thu, Jul 16, 2015 at 06:57:30PM +0200, Emmanuel Dreyfus wrote:
 > Hello
 > 
 > I discovered another scenario where force unmount could not work: an
 > unresponsive PUFFS filesystem. The filesystem got out of order during an
 > operation where the filesystem root vnode is locked. As a result, trying
 > to unmount goes this way
 > 
 > sys_unmount -> namei -> namei_tryemulroot -> lookup_once -> VFS_ROOT ->
 > puffs_vfsop_root -> vn_lock -> VOP_LOCK  and we loose.
 > 
 > I can kill the userland process, but the mount remains, an any attempt
 > to touch it sinks in tstile.
 > 
 > Any idea how can that be fixed?

Either make vnode locks interruptible, or debug puffs.

I favor the former, but lost the argument a few years back. Others
(including e.g. yamt) said no.

-- 
David A. Holland
dholland%netbsd.org@localhost