linux-kernel - Re: [PATCH v5 5/7] revocable: Add fops replacement

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Message-ID: <bee969ed-c050-43a4-961c-07443a45943c@kernel.org>
Date: Fri, 17 Oct 2025 20:19:06 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Tzung-Bi Shih <tzungbi@...nel.org>, Benson Leung <bleung@...omium.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J . Wysocki" <rafael@...nel.org>, Jonathan Corbet <corbet@....net>,
 Shuah Khan <shuah@...nel.org>, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, chrome-platform@...ts.linux.dev,
 linux-kselftest@...r.kernel.org,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Bartosz Golaszewski <brgl@...ev.pl>,
 Wolfram Sang <wsa+renesas@...g-engineering.com>,
 Simona Vetter <simona.vetter@...ll.ch>,
 Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v5 5/7] revocable: Add fops replacement

On 10/17/25 6:37 PM, Jason Gunthorpe wrote:
> On Fri, Oct 17, 2025 at 06:29:10PM +0200, Danilo Krummrich wrote:
> 
>> I'm not sure about MISC device though. Unless there's a good reason,
>> I think MISC device should be "fenced" instead.
> 
> misc is a very small wrapper around raw fops, and raw fops are
> optimized for performance. Adding locking that many important things
> like normal files don't need to all fops would not be agreed.
> 
> The sketch in this series where we have a core helper to provide a
> shim fops that adds on the lock is smart and I think could be an
> agreeable way to make a synchronous misc and cdev unregister for
> everyone to trivially use.

Sure, for MISC devices without a parent for instance there are no device
resources to access anyways.