linux-kernel - Re: [PATCH AUTOSEL 5.14 04/25] cxl/pci: Introduce cdevm_file

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Date:   Tue, 14 Sep 2021 08:42:04 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        Ben Widawsky <ben.widawsky@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linux-cxl@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.14 04/25] cxl/pci: Introduce cdevm_file_operations

On Mon, Sep 13, 2021 at 3:33 PM Sasha Levin <sashal@...nel.org> wrote:
>
> From: Dan Williams <dan.j.williams@...el.com>
>
> [ Upstream commit 9cc238c7a526dba9ee8c210fa2828886fc65db66 ]
>
> In preparation for moving cxl_memdev allocation to the core, introduce
> cdevm_file_operations to coordinate file operations shutdown relative to
> driver data release.
>
> The motivation for moving cxl_memdev allocation to the core (beyond
> better file organization of sysfs attributes in core/ and drivers in
> cxl/), is that device lifetime is longer than module lifetime. The cxl_pci
> module should be free to come and go without needing to coordinate with
> devices that need the text associated with cxl_memdev_release() to stay
> resident. The move will fix a use after free bug when looping driver
> load / unload with CONFIG_DEBUG_KOBJECT_RELEASE=y.
>
> Another motivation for passing in file_operations to the core cxl_memdev
> creation flow is to allow for alternate drivers, like unit test code, to
> define their own ioctl backends.

Hi Sasha,

Please drop this. It's not a fix, it's just a reorganization for
easing the addition of new features and capabilities.