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Date:   Thu, 22 Jun 2023 16:51:18 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     David Howells <dhowells@redhat.com>
Cc:     Marcel Holtmann <marcel@holtmann.org>, linux-cachefs@redhat.com,
        linux-kernel@vger.kernel.org, arnd@arndb.de
Subject: Re: [PATCH] cachefiles: allocate static minor for /dev/cachefiles
Message-ID: <2023062245-synopses-scared-9d96@gregkh>
References: <20230615160806.94000-1-marcel@holtmann.org>
 <1886146.1687441374@warthog.procyon.org.uk>
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On Thu, Jun 22, 2023 at 02:42:54PM +0100, David Howells wrote:
> Marcel Holtmann <marcel@holtmann.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