Re: [PATCH v4] block: genhd: don't call probe function with major_names_lock held

From: Greg KH <gregkh@linuxfoundation.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Hannes Reinecke <hare@suse.de>,
	Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>,
	Hillf Danton <hdanton@sina.com>,
	Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>,
	linux-block <linux-block@vger.kernel.org>,
	Tyler Hicks <tyhicks@linux.microsoft.com>,
	Pavel Tatashin <pasha.tatashin@soleen.com>
Subject: Re: [PATCH v4] block: genhd: don't call probe function with major_names_lock held
Date: Wed, 18 Aug 2021 16:41:28 +0200	[thread overview]
Message-ID: <YR0cGE1sgS8+UhXV@kroah.com> (raw)
In-Reply-To: <1f4218ca-9bfa-7d80-1c69-f5902715d8d9@i-love.sakura.ne.jp>

On Wed, Aug 18, 2021 at 11:34:15PM +0900, Tetsuo Handa wrote:
> On 2021/08/18 22:47, Christoph Hellwig wrote:
> > Hi Tetsuo,
> > 
> > I might sound like a broken record, but we need to reduce the locking
> > complexity, not make it worse and fall down the locking cliff.  I did
> > send a suggested series this morning, in which you found a bunch of
> > bugs.  I'd appreciate it if you could use your superior skills to
> > actually help explain the issue and arrive at a common solution that
> > actually simplifies things instead of steaming down the locking cliff
> > full speed.  Thank you very much.
> 
> I posted "[PATCH] loop: break loop_ctl_mutex into loop_idr_spinlock and loop_removal_mutex"
> which reduces the locking complexity while fixing bugs, but you ignored it. Instead,
> you decided to remove cryptoloop module (where userspace doing "modprobe cryptoloop"
> will break). That is, you decided not to provide patches which can be backported.

Do not ever worry about backporting patches.  Worry about getting the
changes and code correct, stable work can come afterwards, if needed.

thanks,

greg k-h