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

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Message-ID: <CAKPOu+8b_xOicarviAw_39b2y5ei9boRFNxxkP19zE5LGZxm=Q@mail.gmail.com>
Date: Wed, 17 Sep 2025 21:25:50 +0200
From: Max Kellermann <max.kellermann@...os.com>
To: Viacheslav Dubeyko <Slava.Dubeyko@....com>
Cc: Xiubo Li <xiubli@...hat.com>, 
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, 
	"ceph-devel@...r.kernel.org" <ceph-devel@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"netfs@...ts.linux.dev" <netfs@...ts.linux.dev>, Alex Markuze <amarkuze@...hat.com>, 
	"stable@...r.kernel.org" <stable@...r.kernel.org>, "idryomov@...il.com" <idryomov@...il.com>, 
	"mjguzik@...il.com" <mjguzik@...il.com>
Subject: Re: [PATCH v2] ceph: fix deadlock bugs by making iput() calls asynchronous

On Wed, Sep 17, 2025 at 9:20 PM Viacheslav Dubeyko
<Slava.Dubeyko@....com> wrote:
> > > > +     WARN_ON_ONCE(!queue_work(ceph_inode_to_fs_client(inode)->inode_wq,
> > > > +                              &ceph_inode(inode)->i_work));
> > >
> > > This function looks like ceph_queue_inode_work() [1]. Can we use
> > > ceph_queue_inode_work()?
> >
> > No, we can not, because that function adds an inode reference (instead
> > of donating the existing reference) and there's no way we can safely
> > get rid of it (even if we would accept paying the overhead of two
> > extra atomic operations).
>
> This function can call iput() too. Should we rework it, then? Also, as a result,
> we will have two similar functions. And it could be confusing.

No. NOT calling iput() is the whole point of my patch. Did you read
the patch description?