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Date: Mon, 6 Nov 2017 14:40:33 +0100
From: David Sterba <dsterba@suse.cz>
To: Anand Jain <anand.jain@oracle.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 06/11] btrfs: document device locking
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On Mon, Nov 06, 2017 at 10:32:48AM +0800, Anand Jain wrote:
> >> + * Lock nesting
> >> + * ------------
> >> + *
> >> + * uuid_mutex
> >> + *   volume_mutex
> 
> I think it should be nested like this, but as of now its not. Ref [1]
>   [1]
>   btrfs: move volume_mutex into the btrfs_rm_device()

Right, this violates the documented rules and I think that's because of
the ambiguous semantic of the uuid_mutex. Here we're using the "on a
mounted filesystem" part so we lock only in the context where this
applies. Again, once volume_mutex is gone, this will be fixed.