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Message-ID: <cc9a24a8-dd3a-9d21-d9a7-5ee4b0ad7a57@deltatee.com>
Date: Thu, 1 Sep 2022 12:14:25 -0600
From: Logan Gunthorpe <logang@...tatee.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
linux-mm@...ck.org, Christoph Hellwig <hch@....de>,
Dan Williams <dan.j.williams@...el.com>,
Jason Gunthorpe <jgg@...pe.ca>,
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>,
Stephen Bates <sbates@...thlin.com>
Subject: Re: [PATCH v9 7/8] PCI/P2PDMA: Allow userspace VMA allocations
through sysfs
On 2022-09-01 10:42, Greg Kroah-Hartman wrote:
> On Thu, Sep 01, 2022 at 10:32:55AM -0600, Logan Gunthorpe wrote:
>> On 2022-09-01 10:20, Greg Kroah-Hartman wrote:
>>> On Thu, Aug 25, 2022 at 09:24:24AM -0600, Logan Gunthorpe wrote:
>>>> + /*
>>>> + * Removing the alloc attribute from sysfs will call
>>>> + * unmap_mapping_range() on the inode, teardown any existing userspace
>>>> + * mappings and prevent new ones from being created.
>>>> + */
>>>> + sysfs_remove_file_from_group(&pdev->dev.kobj, &p2pmem_alloc_attr.attr,
>>>> + p2pmem_group.name);
>>>
>>> Wait, why are you manually removing the sysfs file here? It's part of
>>> the group, if you do this then it is gone for forever, right? Why
>>> manually do this the sysfs core should handle this for you if the device
>>> is removed.
>>
>> We have to make sure the mappings are all removed before the cleanup of
>> devm_memremap_pages() which will wait for all the pages to be freed.
>
> Then don't use devm_ functions. Why not just use the manual functions
> instead as you know when you want to tear this down.
Well we haven't plugged in a remove call into p2pdma, that would be more
work and more interfaces touching the PCI code. Note: this code isn't a
driver but a set of PCI helpers available to other PCI drivers.
Everything that's setup is using the devm interfaces and gets torn down
with the same. So I don't really see the benefit of making the change
you propose.
Logan
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