Re: [PATCH] xfs: return -EINVAL instead of -EUCLEAN when mounting non-xfs

[Ben Myers <bpm@sgi.com>]

Hey,

On Thu, Jan 03, 2013 at 01:19:29PM -0500, Christoph Hellwig wrote:
> 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.

I think there are some EFSCORRUPTED returns that should not result in 'retry
another' behavior.  E.g. mounting an xfs filesystem where super block magic is
good but you have a corrupted log probably shouldn't result in a retry with
ext3.  It is useful to be able to distinguish between that special case of
sb->sb_magic != XFS_SB_MAGIC and a truly corrupted filesystem.

Here EWRONGFS (EINVAL) in the quiet case is better than EFSCORRUPTED, but
unfortunately we still can't tell EWRONGFS from other EINVAL returns in
b_error.  Adding a new errno as Ted suggested might make some sense.

Regards,
	Ben