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Date:   Tue, 5 Jul 2022 18:43:15 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Logan Gunthorpe <logang@deltatee.com>
Cc:     Christoph Hellwig <hch@lst.de>, Jason Gunthorpe <jgg@ziepe.ca>,
        linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
        linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
        linux-mm@kvack.org, iommu@lists.linux-foundation.org,
        Stephen Bates <sbates@raithlin.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Don Dutile <ddutile@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Minturn Dave B <dave.b.minturn@intel.com>,
        Jason Ekstrand <jason@jlekstrand.net>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Xiong Jianxin <jianxin.xiong@intel.com>,
        Bjorn Helgaas <helgaas@kernel.org>,
        Ira Weiny <ira.weiny@intel.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Martin Oliveira <martin.oliveira@eideticom.com>,
        Chaitanya Kulkarni <ckulkarnilinux@gmail.com>,
        Ralph Campbell <rcampbell@nvidia.com>,
        Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH v7 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem()
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On Tue, Jul 05, 2022 at 10:41:52AM -0600, Logan Gunthorpe wrote:
> Using sysfs means we don't need all the messy callbacks from the nvme
> driver, which is a plus. But I'm not sure how we'd get or unmap the
> mapping of a sysfs file or avoid the anonymous inode. Seems with the
> existing PCI resources, it uses an bin_attribute->f_mapping() callback
> to pass back the iomem_get_mapping() mapping on file open.
> revoke_iomem() is then used to nuke the VMAs. I don't think we can use
> the same infrastructure here as that would add a dependency on
> CONFIG_IO_STRICT_DEVMEM; which would be odd. And I'm not sure whether
> there is a better way.

Why can't we do the revoke on the actual sysfs inode?