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Re: How to fix bad superblock or xfs_repair: error - read only 0 of 512

To: Eric Sandeen <sandeen@xxxxxxxxxxx>
Subject: Re: How to fix bad superblock or xfs_repair: error - read only 0 of 512 bytes
From: Roger Willcocks <roger@xxxxxxxxxxxxxxxx>
Date: Tue, 24 Jan 2012 17:25:31 +0000
Cc: Christian Kildau <lists@xxxxxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>
In-reply-to: <4F1ED4DF.40907@xxxxxxxxxxx>
References: <CALx8gnT9tdPRGfVR0puoSVYz_MDDs4FtWtodST5x29GDnL3A_w@xxxxxxxxxxxxxx> <20120123043117.GH15102@dastard> <92CDAC52-1BA1-43A8-8470-0E2DCD916610@xxxxxxxxxxxxx> <4F1E3BD0.7080604@xxxxxxxxxxx> <B1F1FDAB-0D48-48FE-8FFC-F0567780E052@xxxxxxxxxxxxx> <1327414341.24535.582.camel@xxxxxxxxxxxxxxxxxxxxxxxx> <4D396236-D516-4948-8F43-1AED88539BC4@xxxxxxxxxxxxx> <4F1ED341.4010108@xxxxxxxxxxx> <BE48F258-7061-468F-865E-3595D2C28B3B@xxxxxxxxxxxxx> <4F1ED4DF.40907@xxxxxxxxxxx>
On Tue, 2012-01-24 at 09:57 -0600, Eric Sandeen wrote:
> On 1/24/12 9:52 AM, Christian Kildau wrote:
> > On Jan 24, 2012, at 4:50 PM, Eric Sandeen wrote:
> > 
...
> >> Can you run the hdparm command Roger suggested on your original hard 
> >> drive, please?
> > 
> > Sure, here it is:
> > 
> > /dev/sde:
> >  max sectors   = 2930275055/2930277168, HPA is enabled
>                                           ^^^^^^^^^^^^^^
> 
> ding ding ding, we have a winner.
> 
> 2930277168-2930275055 = 2113 which is about how much xfs tried to read past 
> the end.
> 
> Something about the ubuntu upgrade messed with your disk.
> 
> I'd press them very hard to investigate & resolve that.  You can probably use 
> hdparm
> to remove the HPA and get your space back but this is beyond my expertise &
> familiarity.  It'd be interesting to know what is _in_ the HPA area first.
> 

Kernel commit d8d9129ea28e2177749627c82962feb26e8d11e9 added code to
notice if a disk partition extends into the hidden area and 'unlocks'
the hidden area (uses the full disk capacity) if necessary.

But if there's no partition table (the entire disk is formatted as a
single filesystem) the heuristic can't work.

http://www.spinics.net/lists/linux-ide/msg40244.html suggests that
Ubuntu no longer always unlocks, but uses the heuristic above. In the
same message Alan Cox says Ubuntu 'made a bad mistake on that one.'

-- 
Roger Willcocks <roger@xxxxxxxxxxxxxxxx>

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