linux-kernel - Re: [PATCH RFC fs/namespace] Make kern_unmount() use synchronize_rcu

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Message-ID: <20220427150139.GO4285@paulmck-ThinkPad-P17-Gen-1>
Date:   Wed, 27 Apr 2022 08:01:39 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Chris Mason <clm@...com>
Cc:     Christoph Bartoschek <bartoschek@...gle.com>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "riel@...riel.com" <riel@...riel.com>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>
Subject: Re: [PATCH RFC fs/namespace] Make kern_unmount() use
 synchronize_rcu_expedited()

On Wed, Apr 27, 2022 at 12:19:56PM +0000, Chris Mason wrote:
> 
> > On Apr 26, 2022, at 7:11 PM, Paul E. McKenney <paulmck@...nel.org> wrote:
> > 
> > On Wed, Apr 27, 2022 at 12:58:34AM +0200, Christoph Bartoschek wrote:
> >>> 3. https://lore.kernel.org/lkml/20220218183114.2867528-1-riel@surriel.com/
> >>> Refined queue_rcu_work() approach.
> >>> 
> >>> #1 should work, but the resulting IPIs are not going to make the real-time
> >>> guys happy. #2 and #3 have been subject to reasonably heavy testing
> >>> and did fix a very similar issue to the one that you are reporting,
> >>> but last I knew there were doubts about the concurrency consequences.
> >>> 
> >>> Could you please give at least #3 a shot and see if it helps you?
> >> 
> >> I have tried #3 and it works well with my testcases as far as I can see it.
> > 
> > Thank you for giving it a try!
> > 
> > Al, are further adjustments needed to make this patch cover all the
> > corner cases?
> 
> Did we end up addressing all of Al’s comments here?
> 
> https://lore.kernel.org/lkml/YhCFKyVMtOSyBDJh@zeniv-ca.linux.org.uk/

Indeed we have not!  Thank you for the reminder, and I will get with
Rik to look into this.

							Thanx, Paul