Re: make-bcache bug?

[Marc MERLIN <marc@merlins.org>]

On Mon, May 15, 2017 at 08:37:45PM +0200, Kai Krakow wrote:
> Am Mon, 15 May 2017 13:52:09 +0100
> schrieb Nix <nix@esperi.org.uk>:
> 
> > On 14 May 2017, Kai Krakow said:
> > > I had done this previously, too, and had no such message. But I had
> > > to use wipefs anyway because otherwise udev came and triggered the
> > > device for reasons I couldn't really follow.  
> > 
> > udev does a blkid to see how the block device needs to be activated:
> > this relies on precisely the information wipefs removes. Avoiding this
> > problem is why wipefs *exists*. :)
> 
> Yes, but something triggered udev when it shouldn't...
> 
> This ends up in unregistering/stopping the bcache, then wipefs the
> cdev, then look if udev was triggered and eventually stop it again.
> 
> I guess everytime I ran "fdisk -l" to double-check the devices, or
> "lsblk", or "blkid", udev was triggered and re-enabled the bcache. This
> is a race you cannot win. ;-)

Note that this is orthogonal to the problem I reported.
It tells me 
Already a bcache device on /dev/sde2, overwrite with --wipe-bcache
when it fact this does not work, apparently ever.

So either the message gets changed, or 
make-bcache  --wipe-bcache -C /dev/sde2                                               
Device /dev/sde2 already has a non-bcache superblock, remove it using wipefs and wipefs -a
does not happen. there was no non-bcache superblock.

Marc
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