Re: Bug#747653: grub2-common: update-grub adds both devices and a line feed for BTRFS RAID 1 setup

[Martin Steigerwald]

Am Montag, 8. Dezember 2014, 23:09:24 schrieb Andrei Borzenkov:
> В Sat, 06 Dec 2014 12:01:11 +0100
> 
> Martin Steigerwald <address@hidden> пишет:
> > Am Montag, 2. Juni 2014, 19:39:22 schrieb Andrey Borzenkov:
> > > В Sat, 10 May 2014 20:53:34 +0200
> > > 
> > > Martin Steigerwald <address@hidden> пишет:
> > > > Package: grub2-common
> > > > Version: 2.02~beta2-10
> > > > Severity: normal
> > > > 
> > > > Dear Maintainer,
> > > > 
> > > > I am booting my Debian system via a BTRFS RAID 1 which spans a logical
> > > > volume on a Crucial MSATA and Intel SATA SSD each.
> > > > 
> > > > After running update-grub I am getting this in /boot/grub/grub.cfg:
> > > >                 echo    'Linux 3.15.0-rc5-tp520 wird geladen …'
> > > >                 linux   /vmlinuz-3.15.0-rc5-tp520
> > > >                 root=/dev/mapper/sata-debian
> > > >         
> > > >         /dev/mapper/msata-debian ro rootflags=subvol=debian
> > > >         init=/bin/systemd resume=/dev/mapper/sata-swap>
> > > >         
> > > >                 echo    'Initiale Ramdisk wird geladen …'
> > > >                 initrd  /initrd.img-3.15.0-rc5-tp520
> > > > 
> > > > update-grub basically adds both devices of the BTRFS RAID 1 device
> > > > separated by a line feed. For mounting BTRFS RAID 1 tough one of them
> > > > is enough, once btrfs device scan is run, for which I currently use an
> > > > script for initramfs-tools as a work-around as it didn´t work out of
> > > > the box on my last tests[1].
> > > > 
> > > > This behaviour is due to grub-probe which is called by grub-mkconfig
> > > > at line 139
> > > > 
> > > > 138 # Device containing our userland.  Typically used for root=
> > > > parameter.
> > > > 139 GRUB_DEVICE="`${grub_probe} --target=device /`"
> > > > 140 GRUB_DEVICE_UUID="`${grub_probe} --device ${GRUB_DEVICE}
> > > > --target=fs_uuid 2> /dev/null`" || true
> > > > 
> > > > which is called by update-grub returns both devices with a
> > > > linefeed:
> > > > 
> > > > merkaba:~> grub-probe --target=device /
> > > > /dev/mapper/sata-debian
> > > > /dev/mapper/msata-debian
> > > > 
> > > > grub-probe is an ELF binary.
> > > > 
> > > > The following little change workarounds the issue for me:
> > > > 
> > > > merkaba:~> diff -u /usr/sbin/grub-mkconfig.dist
> > > > /usr/sbin/grub-mkconfig
> > > > --- /usr/sbin/grub-mkconfig.dist        2014-05-08 14:35:25.000000000
> > > > +0200
> > > > +++ /usr/sbin/grub-mkconfig     2014-05-10 20:46:00.380096263 +0200
> > > > @@ -136,7 +136,7 @@
> > > > 
> > > >  fi
> > > >  
> > > >  # Device containing our userland.  Typically used for root=
> > > >  parameter.
> > > > 
> > > > -GRUB_DEVICE="`${grub_probe} --target=device /`"
> > > > +GRUB_DEVICE="`${grub_probe} --target=device / | head -1`"
> > > > 
> > > >  GRUB_DEVICE_UUID="`${grub_probe} --device ${GRUB_DEVICE}
> > > >  --target=fs_uuid
> > > >  2> /dev/null`" || true
> > > >  
> > > >  # Device containing our /boot partition.  Usually the same as
> > > >  GRUB_DEVICE.
> > > > 
> > > > But I suppose the real fix is to be made in the binary grub-probe.
> > > 
> > > No, grub-probe is correct; grub needs to know all devices so it can
> > > have full information which drivers it requires to access them.
> > > 
> > > See also
> > > https://lists.gnu.org/archive/html/grub-devel/2014-05/msg00005.html
> > > 
> > > I suggest you discuss it with Colin, but for now I tend to think, fix
> > > should go into 10_linux. May be always use UUID for btrfs.
> > > 
> > > But this sounds like new can of worms :(
> > 
> > Any way on how to proceed on this one?
> 
> Try patch below
> 
> From: Andrei Borzenkov <address@hidden>
> Subject: [PATCH] fix linux kernel root= argument with multidev btrfs
> 
> Btrfs may reside on multiple devices, but only one of them should be
> passed to root= kernel argument. Add two helper functions:
> 
> - get_root_device: select "best" device for the list. For single device
> just return it to skip probing; for multiple devices try to find LVM as
> before but fall back to the first device if not found.
> 
> - find_abstraction: return device with requested abstraction driver from
> the given list.
> 
> Refactor code to use them and reimplement uses_abstraction on top of
> find_abstraction.
> 
> Also replace check for LVM with uses_abstraction in 10_kfreebsd.
> 
> ---
>  util/grub-mkconfig_lib.in   | 50
> ++++++++++++++++++++++++++++++++++----------- util/grub.d/10_kfreebsd.in  |
>  8 +++-----
>  util/grub.d/10_linux.in     | 10 +++++----
>  util/grub.d/20_linux_xen.in | 10 +++++----
>  4 files changed, 53 insertions(+), 25 deletions(-)
> 
> diff --git a/util/grub-mkconfig_lib.in b/util/grub-mkconfig_lib.in

This looks like it needs to be applied to grub sources instead a installed 
grub.

>  # Allow overriding GRUB_CMDLINE_LINUX and GRUB_CMDLINE_LINUX_DEFAULT.

[…]

> tg: (17328db..) u/btrfs-multidev (depends on: master)

Or I can use some version control branch?

I don´t see the branch on

http://git.savannah.gnu.org/cgit/grub.git/refs/heads

Where can I clone it?

And then I just build it and copy over the generated files from the files the 
patch changed manually to my installed grub to test?

I have grub-pc 2.02~beta2-17 debian package installed.

Thanks,
-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7