linux-kernel - Re: [PATCH v11 8/9] PCI/P2PDMA: Allow userspace VMA allocations through sysfs

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Date:   Tue, 25 Oct 2022 01:29:09 +0000
From:   Chaitanya Kulkarni <chaitanyak@...dia.com>
To:     Logan Gunthorpe <logang@...tatee.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
CC:     Christoph Hellwig <hch@....de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        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>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v11 8/9] PCI/P2PDMA: Allow userspace VMA allocations
 through sysfs

On 10/21/22 10:41, Logan Gunthorpe wrote:
> Create a sysfs bin attribute called "allocate" under the existing
> "p2pmem" group. The only allowable operation on this file is the mmap()
> call.
> 
> When mmap() is called on this attribute, the kernel allocates a chunk of
> memory from the genalloc and inserts the pages into the VMA. The
> dev_pagemap .page_free callback will indicate when these pages are no
> longer used and they will be put back into the genalloc.
> 
> On device unbind, remove the sysfs file before the memremap_pages are
> cleaned up. This ensures unmap_mapping_range() is called on the files
> inode and no new mappings can be created.
> 
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---

Reviewed-by: Chaitanya Kulkarni <kch@...dia.com>

-ck