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Date: Thu, 27 May 2010 14:27:58 +0200
From: armin walland <a.walland@...usmr.com>
To: linux-kernel@...r.kernel.org
Subject: Ooops in BTRFS in 2.6.34 / x86_64 when mounting subvolume by name
hi dearest kernel developers, i sent this email to chris mason about a week
ago but didn't receive any reply so i don't know if it actually reached him so
i decided to sent it to the LKML to make sure it would not get lost:
i would like to report to you an Ooops in btrfs when mounting a subvolume by
name. i tried to gather as much information as possible, if you want any more
information i will be happy to provide it.
i first encountered the crash on my hardware machine and i was also able to
reproduce it on a virtualbox vm with which i compiled this report.
i started with a default arch linux x86_64 installation, then compiled a
vanilla 2.6.34 kernel from kernel.org using /proc/config.gz as a basis. the
only changes i made were to compile BTRFS static and not as a module. when
installing i used xfs as root filesystem from where i could then copy the data
to the btrfs subvolume.
my goal is to have a btrfs filesystem with 2 subvolumes:
v_root as the / filesystem
v_home as the /home filesystem
reproduce:
## get latest btrfs-progs
[root@...ost ~]# uname -a
Linux myhost 2.6.34-BREZEL #1 SMP PREEMPT Wed May 19 21:01:33 CEST 2010 x86_64
Intel(R) Xeon(R) CPU W3530 @ 2.80GHz GenuineIntel GNU/Linux
[root@...ost ~]# cd /usr/src
[root@...ost src]# git clone
git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-progs-unstable.git
Initialized empty Git repository in /usr/src/btrfs-progs-unstable/.git/
remote: Counting objects: 1794, done.
remote: Compressing objects: 100% (687/687), done.
remote: Total 1794 (delta 1355), reused 1418 (delta 1103)
Receiving objects: 100% (1794/1794), 537.30 KiB, done.
Resolving deltas: 100% (1355/1355), done.
-> make && make install
## make the filesystem & subvolumes
mkdir -p /mnt/bt01/
[root@...ost ~]# mkfs.btrfs -L bt01 /dev/sda3
WARNING! - Btrfs v0.19-16-g075587c-dirty IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using
fs created label bt01 on /dev/sda3
nodesize 4096 leafsize 4096 sectorsize 4096 size 3.94GB
Btrfs v0.19-16-g075587c-dirty
[root@...ost ~]# mount /dev/sda3 /mnt/bt01/
[root@...ost ~]# cd /mnt/bt01/
[root@...ost bt01]# btrfsctl -S v_root .
operation complete
Btrfs v0.19-16-g075587c-dirty
[root@...ost bt01]# btrfsctl -S v_home .
operation complete
Btrfs v0.19-16-g075587c-dirty
## copy the data
[root@...ost bt01]# cd /
[root@...ost /]# find . -xdev | cpio -pv /mnt/bt01/v_root/
[root@...ost ~]# cd /dev/
[root@...ost ~]# find . -xdev | cpio -pv /mnt/bt01/v_root/dev/
## set the v_root subvolume as default subvolume
[root@...ost ~]# btrfs subvol list /mnt/bt01/
ID 256 top level 5 path v_root
ID 257 top level 5 path v_home
[root@...ost ~]# btrfs subvol set-default 256 /mnt/bt01/
## prepare for reboot:
[root@...ost ~]# umount /mnt/bt01/
[root@...ost ~]# mount /dev/sda3 /mnt/bt01/
[root@...ost ~]# vim /mnt/bt01/etc/fstab
# change /
[...]
/dev/sda3 / btrfs defaults 0 1
[root@...ost ~]# vim /boot/grub/menu.lst
# (0) Arch Linux BTRFS
title Arch Linux BTRFS
root (hd0,0)
kernel /vmlinuz26-BREZEL root=/dev/sda3 ro vga=795
initrd /kernel26-BREZEL.img
## reboot
[root@...ost ~]# reboot; exit
## after reboot: (looks fine)
[root@...ost ~]# df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/sda3 btrfs 4.0G 1.2G 2.3G 34% /
udev tmpfs 10M 116K 9.9M 2% /dev
shm tmpfs 500M 0 500M 0% /dev/shm
/dev/sda1 ext3 236M 33M 192M 15% /boot
## now try to mount the second subvolume as /home with subvol=v_home
[root@...ost ~]# mount -o subvol=v_home /dev/sda3 /home/
mount: /dev/sda3 is not a valid block device
[root@...ost ~]# 2010 May 21 14:31:04 myhost Oops: 0000 [#1] PREEMPT SMP
2010 May 21 14:31:04 myhost last sysfs file:
/sys/devices/virtual/dmi/id/product_uuid
2010 May 21 14:31:04 myhost Stack:
2010 May 21 14:31:04 myhost Call Trace:
2010 May 21 14:31:04 myhost Code: 02 a8 35 00 48 c7 c7 6a c8 5a 81 31 c0 e8 f4
a7 35 00 eb a0 90 90 90 90 90 90 90 90 90 90 90 90 48 8b 87 a0 00 00 00 55 48
89 e5 <48> 8b 88 b8 02 00 00 8b 81 34 04 00 00 0f b7 91 5a 04 00 00 c9
2010 May 21 14:31:04 myhost CR2: 00000000000002b8
2010 May 21 14:31:12 myhost Oops: 0000 [#2] PREEMPT SMP
2010 May 21 14:31:12 myhost last sysfs file:
/sys/devices/virtual/dmi/id/product_uuid
########
i attached 3 screenshots and ocr texts from 3 screens worth of stack trace, i
hope they can be helpful.
########
----------
REBOOT
----------
## now do the same thing but use subvolid instead of subvol:
[root@...ost ~]# btrfs subvolume list /
ID 256 top level 5 path v_root
ID 257 top level 5 path v_home
[root@...ost ~]# mount -o subvolid=257 /dev/sda3 /home/
[root@...ost ~]# df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/sda3 btrfs 4.0G 1.2G 2.3G 34% /
udev tmpfs 10M 116K 9.9M 2% /dev
shm tmpfs 500M 0 500M 0% /dev/shm
/dev/sda1 ext3 236M 33M 192M 15% /boot
/dev/sda3 btrfs 4.0G 1.2G 2.3G 34% /home
works perfectly.
please let me know if you need anything else and thanks a lot for this
marvellous filesystem :)
--
best rgds, armin
please try not to send me HTML emails!
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