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Date:   Fri, 26 Feb 2021 16:10:44 +0100
From:   David Sterba <dsterba@suse.cz>
To:     Anand Jain <anand.jain@oracle.com>
Cc:     Su Yue <l@damenly.su>, Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: [report] lockdep warning when mounting seed device
Message-ID: <20210226151044.GL7604@twin.jikos.cz>
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        Su Yue <l@damenly.su>, Btrfs BTRFS <linux-btrfs@vger.kernel.org>
References: <tuq0pxpx.fsf@damenly.su>
 <50ff53e3-6e6f-bc6d-31dc-ac376ed944ce@oracle.com>
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On Fri, Feb 26, 2021 at 01:01:02PM +0800, Anand Jain wrote:
> On 25/02/2021 12:39, Su Yue wrote:
> > 
> > While playing with seed device(misc/next and v5.11), lockdep complains 
> > the following:
> > 
> > To reproduce:
> > 
> > dev1=/dev/sdb1
> > dev2=/dev/sdb2
> > 
> > umount /mnt
> > 
> > mkfs.btrfs -f $dev1
> > 
> > btrfstune -S 1 $dev1
> > 
> > mount $dev1 /mnt
> > 
> > btrfs device add $dev2 /mnt/ -f
> > 
> > umount /mnt
> > 
> > mount $dev2 /mnt
> > 
> > umount /mnt
> > 
> > 
> 
> In my understanding the commit 01d01caf19ff7c537527d352d169c4368375c0a1
>   (btrfs: move the chunk_mutex in btrfs_read_chunk_tree
>   fixed this bug in 5.9.
> Could you please try this [1] patch,
> [1] 
> https://patchwork.kernel.org/project/linux-btrfs/patch/20200717100525.320697-1-anand.jain@oracle.com/
> Patch [1] still relevant as the device_list_mutex in clone_fs_devices() 
> is redundant. We could remove it as well.

So the fix 01d01caf19ff7c was not sufficient, the lockdep splat is
reproducible.