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From: Tejun Heo <tj@kernel.org>
To: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Yufen Yu <yuyufen@huawei.com>,
	axboe@kernel.dk, linux-block@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, jack@suse.cz, bvanassche@acm.org
Subject: Re: [PATCH v2 3/7] bdi: protect device lifetime with RCU
Date: Wed, 4 Mar 2020 14:15:44 -0500	[thread overview]
Message-ID: <20200304191544.GO189690@mtj.thefacebook.com> (raw)
In-Reply-To: <20200304191026.GC74069@mit.edu>

Hello,

On Wed, Mar 04, 2020 at 02:10:26PM -0500, Theodore Y. Ts'o wrote:
> On Wed, Mar 04, 2020 at 01:50:56PM -0500, Tejun Heo wrote:
> > Lifetime rules in block layer are kinda nebulous. Some of it comes
> > from the fact that some objects are reused. Instead of the usual,
> > create-use-release, they get repurposed to be associated with
> > something else. When looking at such an object from some paths, we
> > don't necessarily have ownership of all of the members.
> 
> I wonder if the current rules should be better documented, and that
> perhaps we should revisit some of them so we can tighten them down?

Oh yeah, that'd be nice for sure. We've been papering over stuff
constantly for probably over a decade now. It'd be really nice if we
could clean the house and have sane nominal lifetime rules for block
objects.

> For things that are likely to be long-lived, such as anything
> corresponding to a bdi or block device, perhaps it would be better if
> the lifetime rules can be made tighter?  The cost of needing to
> release and reallocate longer lived objects is going to be negligible,
> and benefits of improving code readability, reliability, and
> robuestness might be well worth it.

I full-heartedly agree. It's just a lot of historical accumulation and
not a lot of manpower directed at cleaning it up.

Thanks.

-- 
tejun

  reply	other threads:[~2020-03-04 19:15 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
2020-03-04 18:50       ` Tejun Heo
2020-03-04 19:10         ` Theodore Y. Ts'o
2020-03-04 19:15           ` Tejun Heo [this message]
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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