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

[Max Kellermann]

On Wed, Sep 17, 2025 at 10:20 PM Al Viro <viro@xxxxxxxxxxxxxxxxxx> 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 - but since this was
pre-existing code, I thought somebody more clever than I must have
thought of this at some point and I just don't understand it. Or maybe
Ceph is already bugged and my patch just makes hitting the bug more
likely?