Return-Path: Received: from fieldses.org ([173.255.197.46]:56224 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755737AbeEaRe4 (ORCPT ); Thu, 31 May 2018 13:34:56 -0400 Date: Thu, 31 May 2018 13:34:56 -0400 From: "bfields@fieldses.org" To: "Shawn Lu (shawlu)" Cc: Joshua Watt , "trond.myklebust@primarydata.com" , "anna.schumaker@netapp.com" , "jlayton@poochiereds.net" , "linux-nfs@vger.kernel.org" Subject: Re: Is "unmount -f" worked as expected? Message-ID: <20180531173456.GE1298@fieldses.org> References: <8CC8F228-1A66-4A44-A23B-855E33F4D1D5@cisco.com> <0dae4862d6e5b754ba8f90a6391b6645fdf6889a.camel@gmail.com> <20180531151819.GC1298@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, May 31, 2018 at 04:51:49PM +0000, Shawn Lu (shawlu) wrote: > >On 5/31/18, 8:18 AM, "bfields@fieldses.org" wrote: > > > One case is involved with cross mounted nfs from different host. > > > Note: in theory I think there are some deadlocks possible if client and > > server mount each other. (Each host could be waiting on the other one > > to process writes before it can free memory that it needs to make > > progress.) > > Yes. I hope aggressive umount will help by setting a very short grace period and timeout before umount. No, the deadlock isn't an unmounting problem, it's a problem that could happen during normal operation. I don't know if it's easy to reproduce. You'd probably need one or both hosts to be writing to NFS very quickly. --b.