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[156.34.48.30]) by smtp.gmail.com with ESMTPSA id t65sm1006283qkc.52.2020.11.06.09.42.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Nov 2020 09:42:24 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kb5kl-000zVc-Ja; Fri, 06 Nov 2020 13:42:23 -0400 Date: Fri, 6 Nov 2020 13:42:23 -0400 From: Jason Gunthorpe To: Logan Gunthorpe 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 , Christoph Hellwig , Dan Williams , Christian =?utf-8?B?S8O2bmln?= , Ira Weiny , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter Subject: Re: [RFC PATCH 14/15] PCI/P2PDMA: Introduce pci_mmap_p2pmem() Message-ID: <20201106174223.GU36674@ziepe.ca> References: <20201106170036.18713-1-logang@deltatee.com> <20201106170036.18713-15-logang@deltatee.com> <20201106172206.GS36674@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 06, 2020 at 10:28:00AM -0700, Logan Gunthorpe wrote: > > > On 2020-11-06 10:22 a.m., Jason Gunthorpe wrote: > > On Fri, Nov 06, 2020 at 10:00:35AM -0700, Logan Gunthorpe wrote: > >> Introduce pci_mmap_p2pmem() which is a helper to allocate and mmap > >> a hunk of p2pmem into userspace. > >> > >> Signed-off-by: Logan Gunthorpe > >> drivers/pci/p2pdma.c | 104 +++++++++++++++++++++++++++++++++++++ > >> include/linux/pci-p2pdma.h | 6 +++ > >> 2 files changed, 110 insertions(+) > >> > >> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > >> index 9961e779f430..8eab53ac59ae 100644 > >> +++ b/drivers/pci/p2pdma.c > >> @@ -16,6 +16,7 @@ > >> #include > >> #include > >> #include > >> +#include > >> #include > >> #include > >> #include > >> @@ -1055,3 +1056,106 @@ ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev, > >> return sprintf(page, "%s\n", pci_name(p2p_dev)); > >> } > >> EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show); > >> + > >> +struct pci_p2pdma_map { > >> + struct kref ref; > >> + struct pci_dev *pdev; > >> + void *kaddr; > >> + size_t len; > >> +}; > > > > Why have this at all? Nothing uses it and no vm_operations ops are > > implemented? > > It's necessary to free the allocated p2pmem when the mapping is torn down. That's suspicious.. Once in a VMA the lifetime of the page must be controlled by the page refcount, it can't be put back into the genpool just because the vma was destroed. Jason