From mboxrd@z Thu Jan  1 00:00:00 1970
From: Josef Bacik <jbacik@fusionio.com>
Subject: Re: [PATCH][RESEND] vfs: allow /proc/PID/maps to get device from stat
Date: Wed, 7 Aug 2013 16:51:46 -0400
Message-ID: <20130807205146.GE2397@localhost.localdomain>
References: <20130807195718.GC31381@wotan.suse.de>
 <20130807201826.GA23804@infradead.org>
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Cc: Mark Fasheh <mfasheh@suse.de>, <viro@ZenIV.linux.org.uk>,
	<linux-fsdevel@vger.kernel.org>, <linux-btrfs@vger.kernel.org>,
	Chris Mason <chris.mason@fusionio.com>,
	Josef Bacik <jbacik@fusionio.com>,
	Andrew Vagin <avagin@gmail.com>
To: Christoph Hellwig <hch@infradead.org>
Return-path: <linux-btrfs-owner@vger.kernel.org>
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In-Reply-To: <20130807201826.GA23804@infradead.org>
Sender: linux-btrfs-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

On Wed, Aug 07, 2013 at 01:18:26PM -0700, Christoph Hellwig wrote:
> On Wed, Aug 07, 2013 at 12:57:18PM -0700, Mark Fasheh wrote:
> > stat(2) on btrfs returns a custom device, but proc uses s_dev from the super
> > block. This causes problems (abi breakage) because software (and users) are
> > not expecting the kernel to return different devices from these calls.
> 
> So fix stat on btrfs to return the proper device instead.
> 

Not possible, this will break other things as subvolumes have their own inode
space, it will confuse applications that get multiples of an inode number for
different devices with the same st_dev.  Each subvolume has it's own anonymous
dev to segregate things.  Thanks,

Josef