Need to update for XFS crc=1 (non-default) on-disk format change

[Peter Cordes]

Filing a note here in case I forget later.

It looks like GRUB (2.02-beta2-15) in 14.10 doesn't support XFS's new on-disk metadata format that has CRCs. (rationale: https://www.kernel.org/doc/Documentation/filesystems/xfs-self-describing-metadata.txt)

mkfs.xfs -m crc=1,finobt=1 /dev/sdXY creates an XFS with the new on-disk format. This is NOT the default, and probably won't be until kernel support for it has been in distros for a while.

redhat bug with some patches from Dec 2014:
https://bugzilla.redhat.com/show_bug.cgi?id=1001279

I haven't yet dug up any changelogs about those patches getting merged into GRUB's upstream git repo.

If there's a PPA, or an easy way to build a .deb from git master (or some other way I can easily test git master on an Ubuntu system), I'd be interested and willing to test this.

Testing confirms that xfs crc support was the issue. I made two plain non-MD partitions to take that out of the equation. I formatted one with XFS defaults, and the other with XFS crc. I copied my fresh ubuntu install into each one. I did grub-install /dev/sda while chrooted into the non-crc xfs, and grub-install /dev/sdb in the CRC one. Booting from sda worked fine.

Booting from sdb (I can tell them apart in the bios boot menu easily, because they're not the same make), I was dropped into the grub rescue shell. I could use grub's ls to see data on the non-crc partition, but not on the crc partition. So it's clear that GRUB doesn't understand the new XFS metadata v5 format.

[Eric (eric-redhat-bugs)]

From the XFS list:

> Just a heads-up: GRUB currently doesn't work on a CRC enabled
> file-system. It will print the following error message:
> "not a correct XFS inode"

This format is still WIP upstream, but we should probably have the issue on the RHEL7 radar since we plan to default to XFS even for /boot.

A simple workaround would be to not enable CRCs for the root fs; this may be done by default in any case.

So this bug may be a WONTFIX or NOTABUG, but I figured we should at least log the issue.

Thanks,
-Eric

[Ric (ric-redhat-bugs)]

We probably do want this support in though - I can imagine we might not always need a broken out /boot?

[Peter (peter-redhat-bugs)]

At the very least can we get a pointer here to some details about the FS feature?

[Eric (eric-redhat-bugs)]

on-disk format stuff has recently been coalesced into libxfs/xfs_format.h

http://oss.sgi.com/cgi-bin/gitweb.cgi?p=xfs/xfs.git;a=blob;f=fs/xfs/libxfs/xfs_format.h

Other than that, we maybe need to do some buddy coding to do this, as I don't think either grub2 or xfs has great up-to-date documentation...

For starters I assume grub2 could just grok new formats, but skip the actual CRC verification... things haven't changed *that* much.

-Eric

[Zach (zach-redhat-bugs)]

https://www.google.com/search?q=add+grub2+support+for+xfs+crc

https://<email address hidden>/msg1288553.html

wget http://download.opensuse.org/repositories/Base:/System/openSUSE_Factory/src/grub2-2.02~beta2-201.4.src.rpm

rpm2cpio grub2-2.02~beta2-201.4.src.rpm | cpio -id

ls *xfs*

grub2-xfs-Add-helper-for-inode-size.patch
grub2-xfs-Convert-inode-numbers-to-cpu-endianity-immediate.patch
grub2-xfs-Fix-termination-loop-for-directory-iteration.patch
grub2-xfs-V5-filesystem-format-support.patch

[Peter Cordes (peter-cordes)]

This will get fixed upstream at some point for sure, so having the bug here is probably only useful as a reminder to check that we have an updated-enough GRUB before the next release, or next LTS release at worst.

[Mathieu Trudel-Lapierre (cyphermox)]

Setting to Triaged/Low, since it's not currently a default in any kind of way. I'll review/test the patches and try to upstream them.

[Peter (peter-redhat-bugs)]

*** Bug 1220844 has been marked as a duplicate of this bug. ***

[Winfrid (winfrid-redhat-bugs)]

I have tested grub2-2.02-0.23.fc23.x86_64 installed on an Fedora 21

I succeeded in booting a CentOS 7 with XFS from the fedora boot menu,
but I still cannot boot a SLED 12 with XFS from the fedora boot menu.

Using my openSUSE 13.2 I can boot CentOS 7 and SLED 12.

If you need more information, please advise me, how to create a log from grub2.

[errata-xmlrpc (errata-xmlrpc-redhat-bugs)]

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHSA-2015-2401.html