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Date: Wed, 5 Sep 2018 22:11:52 +0200
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v5 07/13] block: Add PCI P2P flag for request queue and
 check support for requests
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To: Jens Axboe <axboe@kernel.dk>
Cc: Alex Williamson <alex.williamson@redhat.com>, linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, =?iso-8859-1?B?Suly9G1l?= Glisse <jglisse@redhat.com>, Jason Gunthorpe <jgg@mellanox.com>, Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Bjorn Helgaas <bhelgaas@google.com>, Max Gurtovoy <maxg@mellanox.com>, Christoph Hellwig <hch@lst.de>
List-ID: <linux-nvdimm@lists.01.org>

On Wed, Sep 05, 2018 at 01:54:31PM -0600, Jens Axboe wrote:
> On 9/5/18 1:56 PM, Christoph Hellwig wrote:
> > On Wed, Sep 05, 2018 at 01:45:04PM -0600, Jens Axboe wrote:
> >> The point is that the caller doesn't necessarily know where the bio
> >> will end up, hence the caller can't fully check if the whole stack
> >> supports P2P.
> > 
> > The caller must necessarily know where the bio will end up, as for P2P
> > support we need to query if the bio target is P2P capable vs the
> > source of the P2P memory.
> 
> Then what's the point of having the check at all?

Just an additional little safe guard.  If you think it isn't worth
it I guess we can just drop it for now.
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