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Date:   Wed, 29 Jun 2022 08:48:54 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Logan Gunthorpe <logang@deltatee.com>
Cc:     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>,
        Christoph Hellwig <hch@lst.de>,
        Dan Williams <dan.j.williams@intel.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        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()
Message-ID: <20220629064854.GD17576@lst.de>
References: <20220615161233.17527-1-logang@deltatee.com> <20220615161233.17527-21-logang@deltatee.com>
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On Wed, Jun 15, 2022 at 10:12:32AM -0600, Logan Gunthorpe wrote:
> A pseudo mount is used to allocate an inode for each PCI device. The
> inode's address_space is used in the file doing the mmap so that all
> VMAs are collected and can be unmapped if the PCI device is unbound.
> After unmapping, the VMAs are iterated through and their pages are
> put so the device can continue to be unbound. An active flag is used
> to signal to VMAs not to allocate any further P2P memory once the
> removal process starts. The flag is synchronized with concurrent
> access with an RCU lock.

Can't we come up with a way of doing this without all the pseudo-fs
garbagage?  I really hate all the overhead for that in the next
nvme patch as well.