linux-kernel - Re: [RFC PATCH v2 11/11] nvme-pci: Convert to using dma_map

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Date:   Thu, 11 Mar 2021 18:37:03 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Christian König <christian.koenig@....com>,
        Ira Weiny <iweiny@...el.com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jakowski Andrzej <andrzej.jakowski@...el.com>,
        Minturn Dave B <dave.b.minturn@...el.com>,
        Jason Ekstrand <jason@...kstrand.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Xiong Jianxin <jianxin.xiong@...el.com>
Subject: Re: [RFC PATCH v2 11/11] nvme-pci: Convert to using dma_map_sg for
 p2pdma pages



On 2021-03-11 4:59 p.m., Jason Gunthorpe wrote:
> On Thu, Mar 11, 2021 at 04:31:41PM -0700, Logan Gunthorpe wrote:
>> Convert to using dma_[un]map_sg() for PCI p2pdma pages.
>>
>> This should be equivalent, though support will be somewhat less
>> (only dma-direct and dma-iommu are currently supported).
>>
>> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
>>  drivers/nvme/host/pci.c | 27 +++++++--------------------
>>  1 file changed, 7 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
>> index 7d40c6a9e58e..89ca5acf7a62 100644
>> +++ b/drivers/nvme/host/pci.c
>> @@ -577,17 +577,6 @@ static void nvme_free_sgls(struct nvme_dev *dev, struct request *req)
>>  
>>  }
>>  
>> -static void nvme_unmap_sg(struct nvme_dev *dev, struct request *req)
>> -{
>> -	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
>> -
>> -	if (is_pci_p2pdma_page(sg_page(iod->sg)))
>> -		pci_p2pdma_unmap_sg(dev->dev, iod->sg, iod->nents,
>> -				    rq_dma_dir(req));
>> -	else
>> -		dma_unmap_sg(dev->dev, iod->sg, iod->nents, rq_dma_dir(req));
>> -}
> 
> Can the two other places with this code pattern be changed too?

Yes, if this goes forward, I imagine completely dropping
pci_p2pdma_unmap_sg().

Logan