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Date: Thu, 3 Jan 2013 13:19:29 -0500
From: Christoph Hellwig <hch@infradead.org>
To: Sergei Trofimovich <slyfox@gentoo.org>
Cc: xfs@oss.sgi.com, Alex Elder <elder@kernel.org>,
        Dave Chinner <dchinner@redhat.com>, linux-kernel@vger.kernel.org,
        Ben Myers <bpm@sgi.com>, Phil White <pwhite@sgi.com>
Subject: Re: [PATCH] xfs: return -EINVAL instead of -EUCLEAN when mounting
 non-xfs
Message-ID: <20130103181929.GA23049@infradead.org>
References: <20121230015615.6cc9e03c@sf>
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On Sun, Dec 30, 2012 at 02:16:50AM +0300, Sergei Trofimovich wrote:
> It fixes boot panic when trying to boot from btrfs filesystem.
> kernel tries to mount as xfs and gets fatal -EUCLEAN:
> 
> [    0.170000] VFS: Cannot open root device "ubda" or unknown-block(98,0): error -117
> [    0.170000] Please append a correct "root=" boot option; here are the available partitions:
> [    0.170000] 6200         1048576 ubda  driver: uml-blkdev
> [    0.170000] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(98,0)
> 
> init/do_mounts.c expects only -EINVAL as 'retry another' option.
> Fixes regression introduced by commit 98021821a502db347bd9c7671beeee6e8ce07ea6

Looks reasonable, but  think xfs_readsb should simply be changed to
turn all EFSCORRUPTED returns into EINVAL if loud is not set.  The
place that changes the errno value would also be a perfect place to
comment why we are doing this in the code so that this knowledge doesn't
get lost.