From mboxrd@z Thu Jan  1 00:00:00 1970
From: ming.lei@redhat.com (Ming Lei)
Date: Tue, 12 Dec 2017 23:10:33 +0800
Subject: [PATCH 6/6] nvme: remove .init_request callback
In-Reply-To: <20171212141358.GB7849@lst.de>
References: <20171212110232.12495-1-ming.lei@redhat.com>
 <20171212110232.12495-7-ming.lei@redhat.com>
 <20171212141358.GB7849@lst.de>
Message-ID: <20171212151032.GA15078@ming.t460p>

On Tue, Dec 12, 2017@03:13:58PM +0100, Christoph Hellwig wrote:
> On Tue, Dec 12, 2017@07:02:32PM +0800, Ming Lei wrote:
> > It may cause race by setting 'nvmeq' in nvme_init_request()
> > because .init_request is called inside switching io scheduler, which
> > may happen when the NVMe device is being resetted and its nvme queues
> > are being freed and created. We don't have any sync between the two
> > pathes.
> > 
> > This patch removes the .init_request callback and sets the nvmeq runtime,
> > and fixes the following bug:
> 
> If ->init_request doesn't work for NVMe it won't work for any other
> driver either, so we need to remove it entirely if we can't fix it.
> 
> I'd much rather try to fix it first, though.

Just checked all this uses, and it is a NVMe specific issue, because only
NVMe's .init_request() associates reference of one variable to the request,
and the variable itself may change during the request's lifetime.

And all the following .init_request() have this issue:

	nvme_fc_init_request()
	nvme_rdma_init_request()
	nvme_loop_init_request()
	

Thanks,
Ming