linux-kernel - Re: [PATCH] cachefiles: allocate static minor for /dev/cachefiles

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Message-ID: <2023062245-synopses-scared-9d96@gregkh>
Date:   Thu, 22 Jun 2023 16:51:18 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Marcel Holtmann <marcel@...tmann.org>, linux-cachefs@...hat.com,
        linux-kernel@...r.kernel.org, arnd@...db.de
Subject: Re: [PATCH] cachefiles: allocate static minor for /dev/cachefiles

On Thu, Jun 22, 2023 at 02:42:54PM +0100, David Howells wrote:
> Marcel Holtmann <marcel@...tmann.org> wrote:
> 
> > The cachefiles misc character device uses MISC_DYNAMIC_MINOR and thus
> > doesn't support module auto-loading. Assign a static minor number for it
> > and provide appropriate module aliases for it. This is enough for kmod to
> > create the /dev/cachefiles device node on startup and facility module
> > auto-loading.
> 
> Why?  The systemd unit file for it just modprobe's the module first.  It's a
> specialist device file only for use by the appropriate daemon.

And you really don't want to have auto-module-loading when trying to
open a /dev/foo file, that way lies madness in the past, please let's
learn from our mistakes :)

thanks,

greg k-h