Goffredo Baroncelli, Thu, 10 Feb 2011 19:24:57 +0100:

On 02/09/2011 09:12 PM, Lubos Kolouch wrote:

quoted

Goffredo Baroncelli, Wed, 09 Feb 2011 19:25:34 +0100:

quoted

On 02/08/2011 10:26 PM, Lubos Kolouch wrote:

quoted

Goffredo Baroncelli, Tue, 08 Feb 2011 21:00:25 +0100:

quoted

On 02/08/2011 07:57 AM, Lubos Kolouch wrote:

quoted

Hi,

I'm hitting this issue - sda5 is a normal device, nothing to do
with loop, encryption etc.

# mkfs.btrfs /dev/sda5

WARNING! - Btrfs v0.19-35-g1b444cd-dirty IS EXPERIMENTAL WARNING! -
see http://btrfs.wiki.kernel.org before using

error checking /dev/sda5 mount status

Is there something I can do to resolve this?

Some months ago I posted a patch [*] which allows to create a
filesystem even if an integrity tests fail. Anyway it would be
interesting understand why mkfs.btrfs fails. It is possible to have
a strace of the command ?

here ... http://paste.pocoo.org/show/334638/ but it is not in chroot,
it is in "normal" system

Lubos

Hi Lubos,

Could you post also the output of "cat /proc/mounts" command and the
output of "btrfs filesystem show" command. I cannot understand what
should be the problem.

Hi Goffredo,

Sure,
# cat /proc/mounts

rootfs / rootfs rw 0 0
/dev/root / btrfs rw,noatime,compress,ssd 0 0 proc /proc proc
rw,nosuid,nodev,noexec,relatime 0 0 rc-svcdir /lib/rc/init.d tmpfs
rw,nosuid,nodev,noexec,relatime,size=1024k,mode=755 0 0 sysfs /sys
sysfs rw,nosuid,nodev,noexec,relatime 0 0 securityfs
/sys/kernel/security securityfs rw,nosuid,nodev,noexec,relatime 0 0
debugfs /sys/kernel/debug debugfs rw,nosuid,nodev,noexec,relatime 0 0
udev /dev devtmpfs
rw,nosuid,relatime,size=10240k,nr_inodes=217934,mode=755 0 0 fusectl
/sys/fs/fuse/connections fusectl rw,relatime 0 0 none /dev/pts devpts
rw,relatime,mode=600,ptmxmode=000 0 0 none /dev/shm tmpfs rw,relatime 0
0
/dev/sda1 /boot ext2 rw,relatime,errors=continue 0 0 none
/var/tmp/portage tmpfs rw,relatime 0 0 binfmt_misc
/proc/sys/fs/binfmt_misc binfmt_misc rw,nosuid,nodev,noexec,relatime 0
0
/dev/mapper/_dev_sda6 /home btrfs rw,noatime,compress,ssd 0 0

# btrfs filesystem show

Label: none  uuid: fd070c17-e98b-4b50-9fa8-3453482aafa2
	Total devices 1 FS bytes used 5.51GB
	devid    1 size 18.64GB used 10.79GB path /dev/sda2

Label: none  uuid: bf9a1b00-f8bd-44d3-b140-10eea088a60e
	Total devices 1 FS bytes used 6.73GB
	devid    1 size 19.54GB used 19.54GB path /dev/sda5

Label: none  uuid: ae0ba016-1945-4e7a-9fb4-e9311d199727
	Total devices 1 FS bytes used 57.50GB devid    1 size 78.91GB used
	78.91GB path /dev/dm-0

# mkfs.btrfs /dev/sda5

WARNING! - Btrfs v0.19-35-g1b444cd-dirty IS EXPERIMENTAL WARNING! - see
http://btrfs.wiki.kernel.org before using

error checking /dev/sda5 mount status

Also, I can mount it no problem - strange, isn't it

Ok, I think to have track down the problem. To me it seems a bug in
mkfs.btrfs.

The first thing that should be highlighted is that you are trying to
format an already btrfs formatted device. In this there is not anything
wrong.

However, before formatting a device mkfs.btrfs performs some sanity
check. It checks if the device is already mounted, scanning
/proc/mounts.

In a normal case (the device which will be formatted doesn't contain a
btrfs filesystem), mkfs.btrfs is smart enough to don't check device
which are in /proc/mounts bat doesn't exist (like /dev/root).

Instead when the device which will be formatted already contains a btrfs
filesystem, mkfs.btrfs performs a different checks. In fact it considers
also the case of a multi-device based btrfs filesystem. However in this
case it doesn't skip a not existent device but it raises an error. I
think that this is a bug.

As workaround I suggest the following: make a link between the real root
device and /dev/root.

It should be sufficient to format the device.

Hello - you are right...

# ln -s /dev/sda2 /dev/root

# mkfs.btrfs /dev/sda5

WARNING! - Btrfs v0.19-35-g1b444cd-dirty IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using

fs created label (null) on /dev/sda5
	nodesize 4096 leafsize 4096 sectorsize 4096 size 19.54GB
Btrfs v0.19-35-g1b444cd-dirty


Lubos