linux-kernel - Re: [PATCH] Driver Core: devtmpfs - kernel-maintained tmpfs-based /dev

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Message-ID: <9b2b86520908051355o79699e99ke045b635c6b443ad@mail.gmail.com>
Date:	Wed, 5 Aug 2009 21:55:49 +0100
From:	Alan Jenkins <sourcejedi.lkml@...glemail.com>
To:	Greg KH <greg@...ah.com>
Cc:	linux-kernel@...r.kernel.org, Kay Sievers <kay.sievers@...y.org>,
	Jan Blunck <jblunck@...e.de>, gregkh@...e.de,
	Harald Hoyer <harald@...hat.com>,
	Scott James Remnant <scott@...ntu.com>
Subject: Re: [PATCH] Driver Core: devtmpfs - kernel-maintained tmpfs-based 
	/dev

On 8/5/09, Greg KH <greg@...ah.com> wrote:
> Here's the devtmpfs patch again.  For .32 it's a simple and clean patch.
> It's been tested and agreed by three major distros that this is a good
> idea.  SuSE has been shipping this in their kernels for a while now with
> no problems, and actual speedups measured on their boot times.  Gentoo
> also has been testing it, but we haven't gotten a tested-by: line from
> them yet, hopefully that will happen soon.
>
> A number of embedded distros have also privately said they would be
> using this patch, I really don't understand why they don't publically
> want to state this, but oh well...
>
> It's been in linux-next for many months now, with no reported
> regressions at all as well.
>
> thanks,
>
> greg k-h
>
> --------------
>
>
> From: Kay Sievers <kay.sievers@...y.org>
>
> Devtmpfs lets the kernel create a tmpfs instance called devtmpfs
> very early at kernel initialization, before any driver-core device
> is registered. Every device with a major/minor will provide a
> device node in devtmpfs.
>
> Devtmpfs can be changed and altered by userspace at any time,
> and in any way needed - just like today's udev-mounted tmpfs.
> Unmodified udev versions will run just fine on top of it, and will
> recognize an already existing kernel-created device node and use it.
> The default node permissions are root:root 0600. Proper permissions
> and user/group ownership, meaningful symlinks, all other policy still
> needs to be applied by userspace.

> +	err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
> +			      path, LOOKUP_PARENT, &nd);
> +	if (err == 0) {
> +		struct dentry *dentry;
> +
> +		/* create directory right away */
> +		dentry = lookup_create(&nd, 1);
> +		if (!IS_ERR(dentry)) {
> +			err = vfs_mkdir(nd.path.dentry->d_inode,
> +					dentry, 0775);

Is there a typo here?  I think the mode should be 0755.   0755 is used
below, and that does fit better with the 0600 mode for device nodes.

Thanks
Alan
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