From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Mason <chris.mason@oracle.com>
Subject: Re: Warning: bad fsid on block 20971520
Date: Wed, 11 Jan 2012 11:37:14 -0500
Message-ID: <20120111163714.GE2179@shiny>
References: <20120111154621.GX7322@twin.jikos.cz>
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To: linux-btrfs@vger.kernel.org
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In-Reply-To: <20120111154621.GX7322@twin.jikos.cz>
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On Wed, Jan 11, 2012 at 04:46:21PM +0100, David Sterba wrote:
> Hi,
> 
> the $subj warning appears sometimes in syslog, in my case when
> xfstests/209 runs looped. The minimal reproducer is looped mkfs+mount.

I've been seeing this as well.  It's new with 3.2, and I haven't yet
been able to track it down.

The first thing that happens when we mount the FS is a block layer
invalidate, and that must be dropping the write.

It's also possible (but very unlikely) that mkfs.btrfs is neglecting to
write that block.

Do you have a reliable way to reproduce?  If so, can you try with a much
older mkfs.btrfs.

-chris