Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37;
Message-ID: <93ee22bc-b357-4291-b3d9-07ff2cd6c87b@quicinc.com>
Date:   Tue, 12 Dec 2023 08:58:16 -0800
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v7 3/3] check-module-params: Introduce
 check-module-params.sh
Content-Language: en-US
To:     Christoph Hellwig <hch@infradead.org>
CC:     Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        "Nicolas Schier" <nicolas@fjasle.eu>,
        Jonathan Corbet <corbet@lwn.net>,
        <linux-kbuild@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-arm-msm@vger.kernel.org>, <kernel@quicinc.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rob Herring" <robh@kernel.org>,
        Carlos O'Donell <carlos@redhat.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Bjorn Andersson <andersson@kernel.org>,
        Todd Kjos <tkjos@google.com>,
        Matthias Maennich <maennich@google.com>,
        Giuliano Procida <gprocida@google.com>,
        <kernel-team@android.com>, <libabigail@sourceware.org>,
        Dodji Seketeli <dodji@redhat.com>,
        Trilok Soni <quic_tsoni@quicinc.com>,
        "Satya Durga Srinivasu Prabhala" <quic_satyap@quicinc.com>,
        Jordan Crouse <jorcrous@amazon.com>
References: <20231212020259.2451253-1-quic_johmoo@quicinc.com>
 <20231212020259.2451253-4-quic_johmoo@quicinc.com>
 <ZXgOpRzNYGtiE35T@infradead.org>
From:   John Moon <quic_johmoo@quicinc.com>
In-Reply-To: <ZXgOpRzNYGtiE35T@infradead.org>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 12/11/2023 11:41 PM, Christoph Hellwig wrote:
> On Mon, Dec 11, 2023 at 06:02:59PM -0800, John Moon wrote:
>> One part of maintaining backwards compatibility with older
>> userspace programs is avoiding changes to module parameters.
> 
> Really?  I don't think module parameters are a UAPI in the traditional
> sense.  

Agreed, they're not UAPI in the traditional sense. But, we're trying to 
establish tooling to help the community stabilize all interfaces that 
cross the kernel <-> userspace boundary and module params do fall into 
that bucket.

> Now if you break a heavily used one you got to fix it, but
> applying strict stability guarantees on module options which are not
> availble to normal users or even normal programs doesn't make a whole
> lot of sense.
> 

True, but unfortunately we don't have any heuristic to determine if a 
param is "heavily used". However, in this rev, we added the ability to 
parse the permissions of a module param, so we could add a filter which 
does not flag change/removal of params with 0{0,4,6}000 permissions.

It's also obviously fine if the community has no interest in the script. 
We just wanted to share it as we find it to be a useful supplement to 
our code reviews and thought maintainers may find it useful as well.

Cheers,
John