linux-kernel - Re: WARN when unmounting a subvolume that is being synced

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Message-ID: <20180314142852.GA19493@cisco>
Date:   Wed, 14 Mar 2018 08:28:52 -0600
From:   Tycho Andersen <tycho@...ho.ws>
To:     Nikolay Borisov <nborisov@...e.com>
Cc:     linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: WARN when unmounting a subvolume that is being synced

On Wed, Mar 14, 2018 at 09:46:07AM +0200, Nikolay Borisov wrote:
> 
> 
> On 14.03.2018 05:10, Tycho Andersen wrote:
> > Hi all,
> > 
> > I'm getting the WARN below. I think (?) what I'm doing when I get it
> > is that I'm unmounting a subvolume while it's being synced (concurrent
> > uses of the subvolume, at least, happy to look into it further if the
> > stack trace is not so useful). Anyway, I can fairly reliably reproduce
> > this on 4.16-rc4.
> > 
> > Thoughts?
> 
> Yeah, you've mounted the filesystem with flushoncommit. THe easiest
> thing would be to remount with that option ommitted i.e the default
> behavior. This is a well-known issue, unfortunately fixing it is a bit
> hairy and deadlock prone against fs freeze.

Excellent, thanks!

Tycho