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Date: Tue, 5 Dec 2023 17:27:28 +1100
From: Dave Chinner <david@fromorbit.com>
To: NeilBrown <neilb@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
	Christian Brauner <brauner@kernel.org>,
	Jens Axboe <axboe@kernel.dk>, Oleg Nesterov <oleg@redhat.com>,
	Chuck Lever <chuck.lever@oracle.com>,
	Jeff Layton <jlayton@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-nfs@vger.kernel.org
Subject: Re: [PATCH 1/2] Allow a kthread to declare that it calls
 task_work_run()
Message-ID: <ZW7C0Cq+WZz+fnaS@dread.disaster.area>
References: <20231204014042.6754-1-neilb@suse.de>
 <20231204014042.6754-2-neilb@suse.de>
 <20231204024031.GV38156@ZenIV>
 <170172483155.7109.15983228851050210918@noble.neil.brown.name>
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In-Reply-To: <170172483155.7109.15983228851050210918@noble.neil.brown.name>

On Tue, Dec 05, 2023 at 08:20:31AM +1100, NeilBrown wrote:
> On Mon, 04 Dec 2023, Al Viro wrote:
> > On Mon, Dec 04, 2023 at 12:36:41PM +1100, NeilBrown wrote:
> > 
> > > This means that any cost for doing the work is not imposed on the kernel
> > > thread, and importantly excessive amounts of work cannot apply
> > > back-pressure to reduce the amount of new work queued.
> > 
> > It also means that a stuck ->release() won't end up with stuck
> > kernel thread...
> 
> Is a stuck kernel thread any worse than a stuck user-space thread?
> 
> > 
> > > earlier than would be ideal.  When __dput (from the workqueue) calls
> > 
> > WTF is that __dput thing?  __fput, perhaps?
> 
> Either __fput or dput :-)
> ->release isn't the problem that I am seeing.
> The call trace that I see causing problems is
> __fput -> dput -> dentry_kill -> destroy_inode -> xfs_fs_destroy_inode

What problem, exactly, are you having with xfs_fs_destroy_inode()?

-Dave.
-- 
Dave Chinner
david@fromorbit.com