linux-kernel - Re: [PATCH] init: fix name of root device in /proc/mounts

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Date:	Wed, 20 Mar 2013 08:02:41 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Rob Landley <rob@...dley.net>, William Hubbs <w.d.hubbs@...il.com>
CC:	linux-kernel@...r.kernel.org, mpagano@...too.org, ryao@...too.org,
	gregkh@...too.org, torvalds@...ux-foundation.org
Subject: Re: [PATCH] init: fix name of root device in /proc/mounts

Yes, but the current udev maintainer refuses to.

Rob Landley <rob@...dley.net> wrote:

>On 03/19/2013 07:20:17 PM, William Hubbs wrote:
>> On Tue, Mar 19, 2013 at 04:17:11PM -0700, H. Peter Anvin wrote:
>> > On 03/19/2013 03:28 PM, William Hubbs wrote:
>> > > The issue is that /dev/root appears in /proc/mounts if you do not
>> > > boot with an initramfs, but /dev/root is not a device node. In
>the
>> > > past, udev created a symbolic link from /dev/root to the
>> > > appropriate block device, but it does not do this any longer.  
>> Also,
>> > > devtmpfs does not create this symbolic link.
>> > >
>> > > This is causing bugs with software that depends on the existence
>> > > of /dev/root [2] for example.
>> >
>> > Seems okay to me, although even better would be to use the udev
>name
>> > of the device in question.
>> 
>> I'm not following what you mean.
>> 
>> The problem is that "/dev/root" should not be in /proc/mounts,
>> since there is always another entry that points to the root
>> file system.
>
>What gave you that idea?
>
>wget http://landley.net/aboriginal/bin/system-image-i686.tar.bz2
>extract it and ./run-emulator.sh and in there:
>
>(i686:1) /home # cat /proc/mounts
>rootfs / rootfs rw 0 0
>/dev/root / squashfs ro,relatime 0 0
>proc /proc proc rw,relatime 0 0
>sys /sys sysfs rw,relatime 0 0
>dev /dev devtmpfs rw,relatime,size=63072k,nr_inodes=15768,mode=755 0 0
>dev/pts /dev/pts devpts rw,relatime,mode=600 0 0
>/tmp /tmp tmpfs rw,relatime 0 0
>/home /home tmpfs rw,relatime 0 0
>
>Userspace can totally determine what /dev/root points to, I made mdev  
>do it in 2006 (udev started doing so shortly thereafter). Busybox git  
>commit a7e3d052.
>
>Heck, the userspace "stat /" command says "Device: 801h" and /dev/sda1 
>
>is 08:01 on my netbook.
>
>Rob

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