linux-kernel - Re: [PATCH v2] ceph: fix deadlock bugs by making iput() calls asynchronous

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Message-ID: <CAKPOu+8vf5DbR=cJ5dArut=QamTu-EdpJVta_Dsk+dQDpY68UQ@mail.gmail.com>
Date: Wed, 17 Sep 2025 22:27:42 +0200
From: Max Kellermann <max.kellermann@...os.com>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: slava.dubeyko@....com, xiubli@...hat.com, idryomov@...il.com, 
	amarkuze@...hat.com, ceph-devel@...r.kernel.org, netfs@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	Mateusz Guzik <mjguzik@...il.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2] ceph: fix deadlock bugs by making iput() calls asynchronous

On Wed, Sep 17, 2025 at 10:25 PM Max Kellermann
<max.kellermann@...os.com> wrote:
>
> On Wed, Sep 17, 2025 at 10:20 PM Al Viro <viro@...iv.linux.org.uk> wrote:
> >
> > On Wed, Sep 17, 2025 at 03:59:07PM +0200, Max Kellermann wrote:
> >
> > > After advice from Mateusz Guzik, I decided to do the latter.  The
> > > implementation is simple because it piggybacks on the existing
> > > work_struct for ceph_queue_inode_work() - ceph_inode_work() calls
> > > iput() at the end which means we can donate the last reference to it.
> > >
> > > This patch adds ceph_iput_async() and converts lots of iput() calls to
> > > it - at least those that may come through writeback and the messenger.
> >
> > What would force those delayed calls through at fs shutdown time?
>
> I was wondering the same a few days ago, but found no code to enforce
> wait for work completion during shutdown

What about flush_fs_workqueues() in fs/ceph/super.c? Is this what
you're looking for, Al?