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Re: [PATCH] use UUID to map system devices to grub devices
From: |
Felix Zielcke |
Subject: |
Re: [PATCH] use UUID to map system devices to grub devices |
Date: |
Mon, 10 Aug 2009 14:46:13 +0200 |
Am Montag, den 10.08.2009, 13:31 +0200 schrieb Robert Millan:
> On Sat, Aug 08, 2009 at 07:13:20AM +0200, Felix Zielcke wrote:
> > Am Freitag, den 07.08.2009, 21:22 +0200 schrieb Robert Millan:
> > > On Fri, Aug 07, 2009 at 04:29:00PM +0200, Felix Zielcke wrote:
> > > > Am Freitag, den 07.08.2009, 13:27 +0200 schrieb Robert Millan:
> > > > > On Wed, Aug 05, 2009 at 08:18:29AM +0200, Felix Zielcke wrote:
> > > > > > Am Dienstag, den 04.08.2009, 23:19 +0200 schrieb Robert Millan:
> > > > > > > On Fri, Jul 31, 2009 at 06:26:51PM +0200, Felix Zielcke wrote:
> > > > > > > >
> > > > > > > > If we'd do an arbitrary mapping then `grub-probe -t drive'
> > > > > > > > would show
> > > > > > > > the wrong grub device.
> > > > > > > > But except from this I think that would be okay.
> > > > > > >
> > > > > > > We can never garantee that `grub-probe -t drive' will show the
> > > > > > > "right" drive,
> > > > > > > at least on i386-pc, because we don't know how is BIOS going to
> > > > > > > order them.
> > > > > >
> > > > > > Yes drive not, but the partition.
> > > > >
> > > > > It's true, but we don't really make the distinction. UUID search
> > > > > will find
> > > > > a filesystem, which is in a partition (usually), and doesn't rely on
> > > > > partitions
> > > > > being reliable.
> > > > >
> > > > > That's fortunate! It means we don't have to commit to partition
> > > > > numbers being
> > > > > reliable, even if they are right now.
> > > > >
> > > > > Because of this (unless I missed something), at the end of the day the
> > > > > unreliability issue you described doesn't translate into any real
> > > > > problem
> > > > > for us. It just adds more to a problem we already solved.
> > > > >
> > > > > > Unfortunately we don't have UUID support on every filesystem we
> > > > > > support
> > > > > > like JFS. But I think it's not that commonly used.
> > > > >
> > > > > Adding UUID support to new filesystems is very easy. I did the first
> > > > > ones
> > > > > with just 5-10 minutes of research and a few lines of coding.
> > > > >
> > > > > Would you like to do JFS ?
> > > >
> > > > I did it now for JFS.
> > > >
> > > > I tried it now out with dos_part set to p + 2 with my find_by_uuid patch
> > > > and now I get a `no such partition' error on my dmraid device.
> > > > So we can't use an arbitary mapping in grub_util_biosdisk_get_grub_dev
> > >
> > > Why not?
> >
> > well then we would need to change the partition table parsing code to
> > use the same arbitary mapping for GRUB_UTIL && LINUX then
> > grub_util_biosdisk_get_grub_dev and I think that's not really a proper
> > solution.
>
> Why? In that specific situation, it seems:
>
> - We're unable to obtain partition numbers reliably
>
> - It doesn't matter, because the upper layer will sort that out
Well with the current design of util/hostdisk.c it doestn't work.
I don't know how we can make an arbitary mapping work.
> Though, it'd be much better if we could obtain this information from Linux.
> Did you figure out if the behaviour of that ioctl is a bug or is intentional?
Probable intentional, because device-mapper is also used for LVM for
which HDIO_GETGEO really doestn't make sense.
Someone sent a patch to implement it for device-mapper in 2006 to LKML
[0] but it wasn't accepted.
Now I noticed Andrew Morton said `block_device_operations now has a
standalone `getgeo' method.', which doestn't say me anything if this is
something we can use or if this is purely internal for the kernel.
[0] http://lkml.indiana.edu/hypermail/linux/kernel/0602.1/index.html#0729
--
Felix Zielcke
Proud Debian Maintainer
- Re: [PATCH] use UUID to map system devices to grub devices, Robert Millan, 2009/08/04
- Re: [PATCH] use UUID to map system devices to grub devices, Felix Zielcke, 2009/08/05
- Re: [PATCH] use UUID to map system devices to grub devices, Vladimir 'phcoder' Serbinenko, 2009/08/05
- Re: [PATCH] use UUID to map system devices to grub devices, Robert Millan, 2009/08/07
- Re: [PATCH] use UUID to map system devices to grub devices, Felix Zielcke, 2009/08/07
- Re: [PATCH] use UUID to map system devices to grub devices, Robert Millan, 2009/08/07
- Re: [PATCH] use UUID to map system devices to grub devices, Felix Zielcke, 2009/08/08
- Re: [PATCH] use UUID to map system devices to grub devices, Robert Millan, 2009/08/10
- Re: [PATCH] use UUID to map system devices to grub devices,
Felix Zielcke <=
- Re: [PATCH] use UUID to map system devices to grub devices, Felix Zielcke, 2009/08/10
- Re: [PATCH] use UUID to map system devices to grub devices, Robert Millan, 2009/08/10