From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Mason <chris.mason@oracle.com>
Subject: Re: error during umuont after set-default with 2.6.34-rc2
Date: Mon, 22 Mar 2010 09:38:58 -0400
Message-ID: <20100322133858.GB32521@think>
References: <201003212045.o2LKjBgg002162@indigo.cs.bgu.ac.il>
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Content-Type: text/plain; charset=us-ascii
Cc: linux-btrfs@vger.kernel.org
To: Alexander Piavlo <piavka@cs.bgu.ac.il>
Return-path: <linux-btrfs-owner@vger.kernel.org>
In-Reply-To: <201003212045.o2LKjBgg002162@indigo.cs.bgu.ac.il>
List-ID: <linux-btrfs.vger.kernel.org>

On Sun, Mar 21, 2010 at 10:45:11PM +0200, Alexander Piavlo wrote:
> Hi,
> trying the new btrfs tool and set-default with 2.6.34-rc2 i hit the the
> following problem:
> 
> mkfs.btrfs -d single /dev/sys/btrfs
> mount -t btrfs /dev/sys/btrfs /btrfs
> btrfs subvolume create /btrfs/newroot
> mkdir /btrfs/newroot/.btrfs
> btrfs subvolume set-default 256 /btrfs
> umount /btrfs
> mount -t btrfs /dev/sys/btrfs /btrfs
> 
> up till now everything works ok
> 
> A question How do i access or mount the original root of btrfs? Which
> tree id does it have?
> It would be great if "btrfs subvolume list ..." would also list the
> original root.
> 
> I guessed I need to use 0, so i tried:
>   mount -t btrfs -o subvol=0 /dev/sys/btrfs /btrfs/.btrfs
> and:
>   mount -t btrfs -o subvol=. /dev/sys/btrfs /btrfs/.btrfs
> but in both cases it mounted the newroot subvolume with id 256 under
> /btrfs/.btrfs
> 
> So I tried setting the original root back with:
>   btrfs subvolume set-default 0 /btrfs

Looks like set-default needs to understand 0 means use the old default,
I'll add this in.

btrfs subvolume set-default 5 /btrfs

or mount -o subvolid=0 /dev/xxx /mnt
or mount -o subvolid=5 /dev/xxx /mnt

-chris