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b=NeyCdeiWUHf3IhSEPWgn2DkGBpDRb6SsxBs0RlFNx4Fczo9SA+YQUAs7N7MXjnlwH Gyy1v26ZHQEufa0y5X3aD8gjYfMyeELL8qUE+3IT4CaETrivxjLh7SrcITxVwztza/ VA8AFfg3ajOY04ThGUNZAC11cVEBrJTzICSAA12u+teMxc4mbJA/QuYMUZvA8W15uv whxc0cB3MSr0cZpm7J0awJF375VohEBUdzt/+7tvxuNOcCOiwPY4NzvlReDT3hx+/W B6u9ooKkI5apaP5bHY5GrIGwL9AX47T3mdgiRO06TIrTHWAd4q8mOybhrqk7+Zjwyv MiK8XtH8RPkVw== Date: Wed, 11 Sep 2024 08:51:41 -0500 From: Bjorn Helgaas To: Alistair Popple Cc: dan.j.williams@intel.com, linux-mm@kvack.org, vishal.l.verma@intel.com, dave.jiang@intel.com, logang@deltatee.com, bhelgaas@google.com, jack@suse.cz, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, mpe@ellerman.id.au, npiggin@gmail.com, dave.hansen@linux.intel.com, ira.weiny@intel.com, willy@infradead.org, djwong@kernel.org, tytso@mit.edu, linmiaohe@huawei.com, david@redhat.com, peterx@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, jhubbard@nvidia.com, hch@lst.de, david@fromorbit.com Subject: Re: [PATCH 02/12] pci/p2pdma: Don't initialise page refcount to one Message-ID: <20240911135141.GA629523@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87r09rgfjj.fsf@nvdebian.thelocal> X-Rspam-User: X-Stat-Signature: y99qjcoupefnc74toeos189e4ncrhkr9 X-Rspamd-Queue-Id: 77124120013 X-Rspamd-Server: rspam11 X-HE-Tag: 1726062704-910487 X-HE-Meta: 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 OtXMLroK oT/uogRKkTTillVvSSK3unCDBRzQS/dcmRgrWFhW+S3f2SlpnF3sq0Ym0LctpVYnssndUQIcMyC2oGjCjlDRqDu3IR7oqt1ZzPNzcGE6xspXArfjyhqQyyttwaPrjGbPmdSagxaVX2ngoJSeoJhiJR35TFP19+n4DQrHYJUHwqA6c8FonUuPCw5aqYhEsKZuB3FN7L38CyvL6PyQni6+AAqtMYridk+J66hpdCYDxpEBwlpY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 11, 2024 at 11:07:51AM +1000, Alistair Popple wrote: > > >> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > >> index 4f47a13..210b9f4 100644 > >> --- a/drivers/pci/p2pdma.c > >> +++ b/drivers/pci/p2pdma.c > >> @@ -129,6 +129,12 @@ static int p2pmem_alloc_mmap(struct file *filp, struct kobject *kobj, > >> } > >> > >> /* > >> + * Initialise the refcount for the freshly allocated page. As we have > >> + * just allocated the page no one else should be using it. > >> + */ > >> + set_page_count(virt_to_page(kaddr), 1); > > > > No doubt the subject line is true in some overall context, but it does > > seem to say the opposite of what happens here. > > Fair. It made sense to me from the mm context I was coming from (it was > being initialised to 1 there) but not overall. Something like "move page > refcount initialisation to p2pdma driver" would make more sense? Definitely would, thanks.