Re: [PATCH] Fixing soft NFS umount -f, round 1

[Chuck Silvers <chuq%chuq.com@localhost>]

On Wed, Jul 01, 2015 at 09:10:40PM +0200, Emmanuel Dreyfus wrote:
> David Holland <dholland-tech%netbsd.org@localhost> wrote:
> 
> > ...however, with a dead nfs server even sync() should time out and
> > fail eventually.
> 
> The problem is that you can ask VFS_SYNC(9) to wait or not, but there is
> no such option for sync(2). 

for a soft mount sync() should time out like everything else, yes.
for a hard mount, our current semantics for sync() will cause it to
wait indefinitely.  sync() is not required to wait for anything at all,
so it would be possible to have it not hang even for hard mounts
and even though there's no way to specify wait or no-wait,
but it would probably be a lot of work to get there.

-Chuck