linux-kernel - Re: Killing process in D state on mount to dead NFS server. (when process is in fsync)

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Message-ID: <20140802131946.207c597c@notabene.brown>
Date:	Sat, 2 Aug 2014 13:19:46 +1000
From:	NeilBrown <neilb@...e.de>
To:	Trond Myklebust <trondmy@...il.com>
Cc:	Jeff Layton <jlayton@...chiereds.net>,
	Ben Greear <greearb@...delatech.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: Killing process in D state on mount to dead NFS server. (when
 process is in fsync)

On Fri, 1 Aug 2014 22:55:42 -0400 Trond Myklebust <trondmy@...il.com> wrote:

> > That still leaves some open questions though...
> >
> > Is that enough to fix it? You'd still have the dirty pages lingering
> > around, right? Would a umount -f presumably work at that point?
> 
> 'umount -f' will kill any outstanding RPC calls that are causing the
> mount to hang, but doesn't do anything to change page states or NFS
> file/lock states.

Should it though?

       MNT_FORCE (since Linux 2.1.116)
              Force  unmount  even  if busy.  This can cause data loss.  (Only
              for NFS mounts.)

Given that data loss is explicitly permitted, I suspect it should.

Can we make MNT_FORCE on NFS not only abort outstanding RPC calls, but
fail all subsequent RPC calls?  That might make it really useful.   You
wouldn't even need to "kill -9" then.

NeilBrown

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