linux-kernel - Re: [PATCH 02/12] pci-p2p: Add sysfs group to display p2pmem stats

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Date:   Thu, 4 Jan 2018 16:13:09 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     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,
        Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Keith Busch <keith.busch@...el.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        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>
Subject: Re: [PATCH 02/12] pci-p2p: Add sysfs group to display p2pmem stats



On 04/01/18 02:50 PM, Bjorn Helgaas wrote:
> On Thu, Jan 04, 2018 at 12:01:27PM -0700, Logan Gunthorpe wrote:
>> Attributes display the total amount of P2P memory, the ammount available
>> and whether it is published or not.
> 
> s/ammount/amount/ (also below)

Will fix.

> I wonder if "p2pdma" would be a more suggestive term?  It's not really
> the *memory* that is peer-to-peer; the peer-to-peer part is referring
> to *access* to the memory.

I agree with Jason on this point. For now, it only describes the 
peer-to-peer memory attributes. If we change the directory to p2pdma 
then we'd have to add a mem prefix or something to each attribute.

>> @@ -82,6 +130,9 @@ static int pci_p2pmem_setup(struct pci_dev *pdev)
>>   	if (error)
>>   		goto out_pool_destroy;
>>   
>> +	if (sysfs_create_group(&pdev->dev.kobj, &p2pmem_group))
>> +		dev_warn(&pdev->dev, "failed to create p2p sysfs group\n");
> 
> Not sure the warning (by itself) is worthwhile.  If we were going to
> disable the feature if sysfs_create_group() failed, that's one thing,
> but we aren't doing anything except generating a warning, which the
> user can't really do anything with.  If the user is looking for the
> sysfs file, its absence will be obvious even without the message.

Unfortunately, sysfs_create_group() has the warn_unused_result flag set. 
So I need to do something with the result to squash the warning. I could 
just assign it to an unused variable but something seemed like it needed 
to be done and printing a warning was the easiest thing...

Logan