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Date:   Fri, 12 May 2023 09:16:36 -0600
From:   Tycho Andersen <tycho@tycho.pizza>
To:     Dave Chinner <david@fromorbit.com>
Cc:     "Darrick J . Wong" <djwong@kernel.org>, linux-xfs@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Tycho Andersen <tandersen@netflix.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH] xfs: don't do inodgc work if task is exiting
Message-ID: <ZF5YVNdeVNSoG08p@tycho.pizza>
References: <20230511151702.14704-1-tycho@tycho.pizza>
 <20230512014547.GA3223426@dread.disaster.area>
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On Fri, May 12, 2023 at 11:45:47AM +1000, Dave Chinner wrote:
> 
> Yeah, this is papering over the observed symptom, not addressing the
> root cause of the inodegc flush delay. What do you see when you run
> sysrq-w and sysrq-l? Are there inodegc worker threads blocked
> performing inodegc?

I will try this next time we encounter this.

> e.g. inodegc flushes could simply be delayed by an unlinked inode
> being processed that has millions of extents that need to be freed.
> 
> In reality, inode reclaim can block for long periods of time
> on any filesystem, so the concept of "inode reclaim should
> not block when PF_EXITING" is not a behaviour that we guarantee
> anywhere or could guarantee across the board.
> 
> Let's get to the bottom of why inodegc has apparently stalled before
> trying to work out how to fix it...

I'm happy to try, but I think it is also worth applying this patch.
Like I said in the other thread, having to evac a box to get rid of an
unkillable userspace process is annoying.

Thanks for the debugging tips.

Tycho