linux-kernel - Re: [PATCH v5 13/13] nvmet: Optionally use PCI P2P memory

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Date:   Fri, 31 Aug 2018 09:41:51 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Sagi Grimberg <sagi@...mberg.me>, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-rdma@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-block@...r.kernel.org
Cc:     Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Keith Busch <keith.busch@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Christian König <christian.koenig@....com>,
        Steve Wise <swise@...ngridcomputing.com>
Subject: Re: [PATCH v5 13/13] nvmet: Optionally use PCI P2P memory

Thanks, for the review.

On 30/08/18 06:25 PM, Sagi Grimberg wrote:
>> +	if (req->port->p2p_dev) {
>> +		if (!pci_p2pdma_assign_provider(req->port->p2p_dev,
>> +						&ctrl->p2p_clients)) {
>> +			pr_info("peer-to-peer memory on %s is not supported\n",
>> +				pci_name(req->port->p2p_dev));
>> +			goto free_devices;
>> +		}
>> +		ctrl->p2p_dev = pci_dev_get(req->port->p2p_dev);
>> +	} else {
> 
> When is port->p2p_dev == NULL? a little more documentation would help 
> here...

In the configfs functions, if the user enables p2p (port->use_p2pmem)
using 'auto' or 'y' then port->p2p_dev will be NULL. If the user sets a
specific p2p_dev to use, port->p2p_dev will be set to that device. I can
add a couple comments in the next version.

Logan