linux-kernel - Re: [PATCH v7 20/21] PCI/P2PDMA: Introduce pci_mmap

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Date:   Tue, 5 Jul 2022 18:50:39 +0200
From:   Christoph Hellwig <hch@....de>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     Christoph Hellwig <hch@....de>, Jason Gunthorpe <jgg@...pe.ca>,
        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>,
        Dan Williams <dan.j.williams@...el.com>,
        Christian König <christian.koenig@....com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        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>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Robin Murphy <robin.murphy@....com>,
        Martin Oliveira <martin.oliveira@...eticom.com>,
        Chaitanya Kulkarni <ckulkarnilinux@...il.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v7 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem()

[note for the newcomers, this is about allowing mmap()ing the PCIe
P2P memory from the generic PCI P2P code through sysfs, and more
importantly how to revoke it on device removal]

On Tue, Jul 05, 2022 at 10:44:49AM -0600, Logan Gunthorpe wrote:
> We might be able to. I'm not sure. I'll have to figure out how to find
> that inode from the p2pdma code. I haven't found an obvious interface to
> do that.

I think the right way to approach this would be a new sysfs API
that internally calls unmap_mapping_range internally instead of
exposing the inode. I suspect that might actually be the right thing
to do for iomem_inode as well.