From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Tejun Heo <tj@kernel.org>
Cc: Yufen Yu <yuyufen@huawei.com>,
axboe@kernel.dk, linux-block@vger.kernel.org,
linux-fsdevel@vger.kernel.org, jack@suse.cz, bvanassche@acm.org,
tytso@mit.edu
Subject: Re: [PATCH v2 3/7] bdi: protect device lifetime with RCU
Date: Wed, 4 Mar 2020 18:23:44 +0100 [thread overview]
Message-ID: <20200304172344.GA1864778@kroah.com> (raw)
In-Reply-To: <20200304172221.GA1864270@kroah.com>
On Wed, Mar 04, 2020 at 06:22:21PM +0100, Greg Kroah-Hartman wrote:
> On Wed, Mar 04, 2020 at 12:05:43PM -0500, Tejun Heo wrote:
> > Hello,
> >
> > It might be better to put this patch at the end rather than in the
> > middle so that when this patch is applied things are actually fixed.
> >
> > > +struct bdi_rcu_device {
> > > + struct device dev;
> > > + struct rcu_head rcu_head;
> > > +};
> >
> > (cc'ing Greg)
> >
> > Greg, block layer switches association between backing_device_info and
> > its struct device and needs to protect it with RCU. Yufen did so by
> > introducing a wrapping struct around struct device like above. Do you
> > think it'd make sense to just embed rcu_head into struct device and
> > let put_device() to RCU release by default?
>
> Ugh, I was dreading the fact that this day might sometime come...
>
> In theory, the reference counting for struct device shouldn't need to
> use rcu at all, right? what is driving the need to use rcu for
> backing_device_info? Are these being destroyed/used so often that rcu
> really is the best solution and the existing reference counting doesn't
> work properly?
>
> Some context is needed here.
Ah, would help if I just read the whole patch series, that helps...
Something is odd if kobj->name is the problem here, let me look at the
patches in full.
thanks,
greg k-h
next prev parent reply other threads:[~2020-03-04 17:23 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 11:18 [PATCH v2 0/7] bdi: fix use-after-free for bdi device Yufen Yu
2020-02-26 11:18 ` [PATCH v2 1/7] blk-wbt: use bdi_dev_name() to get device name Yufen Yu
2020-02-26 11:18 ` [PATCH v2 2/7] fs/ceph: " Yufen Yu
2020-02-26 11:18 ` [PATCH v2 3/7] bdi: protect device lifetime with RCU Yufen Yu
2020-03-04 17:05 ` Tejun Heo
2020-03-04 17:22 ` Greg Kroah-Hartman
2020-03-04 17:23 ` Greg Kroah-Hartman [this message]
2020-03-04 18:50 ` Tejun Heo
2020-03-04 19:10 ` Theodore Y. Ts'o
2020-03-04 19:15 ` Tejun Heo
2020-03-04 20:05 ` Greg Kroah-Hartman
2020-03-05 1:22 ` Tejun Heo
2020-03-06 16:25 ` Greg Kroah-Hartman
2020-03-07 9:13 ` Yufen Yu
2020-02-26 11:18 ` [PATCH v2 4/7] bdi: create a new function bdi_get_dev_name() Yufen Yu
2020-02-26 11:18 ` [PATCH v2 5/7] bfq: fix potential kernel crash when print dev err info Yufen Yu
2020-02-26 11:18 ` [PATCH v2 6/7] memcg: fix crash in wb_workfn when bdi unregister Yufen Yu
2020-02-26 11:18 ` [PATCH v2 7/7] blk-wbt: replace bdi_dev_name() with bdi_get_dev_name() Yufen Yu
2020-03-04 17:29 ` [PATCH v2 0/7] bdi: fix use-after-free for bdi device Greg KH
2020-03-04 18:57 ` Tejun Heo
2020-03-04 20:07 ` Greg KH
2020-03-04 19:02 ` Theodore Y. Ts'o
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