* mount a multi-device filesystem using a loopback device
@ 2011-09-07 4:18 Jeff Liu
2011-09-07 4:37 ` cwillu
[not found] ` <4E670FB8.4000705@cn.fujitsu.com>
0 siblings, 2 replies; 6+ messages in thread
From: Jeff Liu @ 2011-09-07 4:18 UTC (permalink / raw)
To: linux-btrfs
Hello,
I was trying to create a multi-device Btrfs filesystem using two
loopback devices, by referring to the following page:
https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices
However, I met a strange thing while mounting the first loop device
without any extra mount options,
1. Create and format two images, the 1st in 400Mbytes, and 2nd in
286Mbytes.
root@pibroch:/btrfs-progs# ls -lh /usr/src/linux-3.0/img*
-rw-r--r-- 1 jeff jeff 400M 2011-09-07 12:00 /usr/src/linux-3.0/img0
-rw-r--r-- 1 jeff jeff 286M 2011-09-07 12:00 /usr/src/linux-3.0/img1
root@pibroch:/btrfs-progs# mkfs.btrfs /usr/src/linux-3.0/img0
/usr/src/linux-3.0/img1
WARNING! - Btrfs v0.19-35-g1b444cd IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using
failed to read /dev/sr0
failed to read /dev/sr0
adding device /usr/src/linux-3.0/img1 id 2
fs created label (null) on /usr/src/linux-3.0/img0
nodesize 4096 leafsize 4096 sectorsize 4096 size 685.50MB
Btrfs v0.19-35-g1b444cd
2. Setup the loopback manually:
root@pibroch:/btrfs-progs# losetup /dev/loop0 /usr/src/linux-3.0/img0
root@pibroch:/btrfs-progs# losetup /dev/loop1 /usr/src/linux-3.0/img1
root@pibroch:/btrfs-progs# losetup -a
/dev/loop0: [0802]:1736614 (/usr/src/linux-3.0/img0)
/dev/loop1: [0802]:1736726 (/usr/src/linux-3.0/img1)
3. Try to mount loop0, it will failed as below:
root@pibroch:/btrfs-progs# mount /dev/loop0 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
4. Try to mount loop1, it works:
root@pibroch:/btrfs-progs# mount /dev/loop1 /mnt
root@pibroch:/btrfs-progs# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 46G 23G 21G 52% /
none 896M 700K 895M 1% /dev
none 957M 80K 957M 1% /dev/shm
none 957M 104K 957M 1% /var/run
none 957M 0 957M 0% /var/lock
/dev/loop1 686M 56K 493M 1% /mnt
5. umount loop1, and try to mount loop0 again, it works at this time:
root@pibroch:/btrfs-progs# umount /mnt
root@pibroch:/btrfs-progs# mount /dev/loop0 /mnt
root@pibroch:/btrfs-progs# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 46G 23G 21G 52% /
none 896M 700K 895M 1% /dev
none 957M 80K 957M 1% /dev/shm
none 957M 104K 957M 1% /var/run
none 957M 0 957M 0% /var/lock
/dev/loop0 686M 56K 493M 1% /mnt
According to my debugging result, for the 1st time, mount loop0 failed
at around volumes.c:3468:
map->stripes[i].dev = btrfs_find_device(root, devid, uuid,
NULL);
if (!map->stripes[i].dev && !btrfs_test_opt(root,
DEGRADED)) {
kfree(map);
free_extent_map(em);
return -EIO;
So I repeat the above steps again, and try to mount loop0 with "-o
degraded" option, it works as expected:
root@pibroch:/btrfs-progs# mount -o degraded /dev/loop0 /mnt
root@pibroch:/btrfs-progs# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 46G 23G 21G 52% /
none 896M 700K 895M 1% /dev
none 957M 140K 957M 1% /dev/shm
none 957M 104K 957M 1% /var/run
none 957M 0 957M 0% /var/lock
/dev/loop0 686M 56K 136M 1% /mnt
kernel version 3.1.0-rc2+.
Is it a bug? or Am I missing something?
Thanks,
-Jeff
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: mount a multi-device filesystem using a loopback device
2011-09-07 4:18 mount a multi-device filesystem using a loopback device Jeff Liu
@ 2011-09-07 4:37 ` cwillu
2011-09-07 6:44 ` Jeff Liu
[not found] ` <4E670FB8.4000705@cn.fujitsu.com>
1 sibling, 1 reply; 6+ messages in thread
From: cwillu @ 2011-09-07 4:37 UTC (permalink / raw)
To: jeff.liu; +Cc: linux-btrfs
> 1. Create and format two images, the 1st in 400Mbytes, and 2nd in 286Mbytes.
> root@pibroch:/btrfs-progs# ls -lh /usr/src/linux-3.0/img*
> -rw-r--r-- 1 jeff jeff 400M 2011-09-07 12:00 /usr/src/linux-3.0/img0
> -rw-r--r-- 1 jeff jeff 286M 2011-09-07 12:00 /usr/src/linux-3.0/img1
Very small btrfs filesystem require special handling, mixed block
groups in particular, which I believe also requires an updated mkfs
from the integration repo.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: mount a multi-device filesystem using a loopback device
[not found] ` <4E670FB8.4000705@cn.fujitsu.com>
@ 2011-09-07 6:42 ` Jeff Liu
0 siblings, 0 replies; 6+ messages in thread
From: Jeff Liu @ 2011-09-07 6:42 UTC (permalink / raw)
To: Li Zefan; +Cc: linux-btrfs
On 09/07/2011 02:31 PM, Li Zefan wrote:
>> Is it a bug? or Am I missing something?
>>
> You need to run this before mounting the devices:
>
> # btrfs device scan
Thank you, it works by executing device scan.
-Jeff
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: mount a multi-device filesystem using a loopback device
2011-09-07 4:37 ` cwillu
@ 2011-09-07 6:44 ` Jeff Liu
2011-09-08 5:32 ` C Anthony Risinger
0 siblings, 1 reply; 6+ messages in thread
From: Jeff Liu @ 2011-09-07 6:44 UTC (permalink / raw)
To: cwillu; +Cc: linux-btrfs
On 09/07/2011 12:37 PM, cwillu wrote:
>> 1. Create and format two images, the 1st in 400Mbytes, and 2nd in 286Mbytes.
>> root@pibroch:/btrfs-progs# ls -lh /usr/src/linux-3.0/img*
>> -rw-r--r-- 1 jeff jeff 400M 2011-09-07 12:00 /usr/src/linux-3.0/img0
>> -rw-r--r-- 1 jeff jeff 286M 2011-09-07 12:00 /usr/src/linux-3.0/img1
> Very small btrfs filesystem require special handling, mixed block
> groups in particular, which I believe also requires an updated mkfs
> from the integration repo.
Thanks for your response, however, even if I enlarged the image size to
2G, still got no luck.
Per Zefan's comments, run 'btrfs device scan' fixed this issue.
-Jeff
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: mount a multi-device filesystem using a loopback device
2011-09-07 6:44 ` Jeff Liu
@ 2011-09-08 5:32 ` C Anthony Risinger
2011-09-08 6:31 ` Jeff Liu
0 siblings, 1 reply; 6+ messages in thread
From: C Anthony Risinger @ 2011-09-08 5:32 UTC (permalink / raw)
To: jeff.liu; +Cc: cwillu, linux-btrfs
On Wed, Sep 7, 2011 at 1:44 AM, Jeff Liu <jeff.liu@oracle.com> wrote:
> On 09/07/2011 12:37 PM, cwillu wrote:
>>>
>>> 1. =C2=A0Create and format two images, the 1st in 400Mbytes, and 2n=
d in
>>> 286Mbytes.
>>> root@pibroch:/btrfs-progs# ls -lh /usr/src/linux-3.0/img*
>>> -rw-r--r-- 1 jeff jeff 400M 2011-09-07 12:00 /usr/src/linux-3.0/img=
0
>>> -rw-r--r-- 1 jeff jeff 286M 2011-09-07 12:00 /usr/src/linux-3.0/img=
1
>>
>> Very small btrfs filesystem require special handling, mixed block
>> groups in particular, which I believe also requires an updated mkfs
>> from the integration repo.
>
> Thanks for your response, however, even if I enlarged the image size =
to 2G,
> still got no luck.
> Per Zefan's comments, run 'btrfs device scan' fixed this issue.
you should be able to achieve this via `device=3D` mount option(s?) as =
well:
https://btrfs.wiki.kernel.org/index.php/Getting_started#Mount_Options
=2E.. for completeness :-) ... and posterity or whatever.
C Anthony
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To unsubscribe from this list: send the line "unsubscribe linux-btrfs" =
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the body of a message to majordomo@vger.kernel.org
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: mount a multi-device filesystem using a loopback device
2011-09-08 5:32 ` C Anthony Risinger
@ 2011-09-08 6:31 ` Jeff Liu
0 siblings, 0 replies; 6+ messages in thread
From: Jeff Liu @ 2011-09-08 6:31 UTC (permalink / raw)
To: C Anthony Risinger; +Cc: cwillu, linux-btrfs
On 09/08/2011 01:32 PM, C Anthony Risinger wrote:
> On Wed, Sep 7, 2011 at 1:44 AM, Jeff Liu<jeff.liu@oracle.com> wrote:
>> On 09/07/2011 12:37 PM, cwillu wrote:
>>>> 1. Create and format two images, the 1st in 400Mbytes, and 2nd in
>>>> 286Mbytes.
>>>> root@pibroch:/btrfs-progs# ls -lh /usr/src/linux-3.0/img*
>>>> -rw-r--r-- 1 jeff jeff 400M 2011-09-07 12:00 /usr/src/linux-3.0/img0
>>>> -rw-r--r-- 1 jeff jeff 286M 2011-09-07 12:00 /usr/src/linux-3.0/img1
>>> Very small btrfs filesystem require special handling, mixed block
>>> groups in particular, which I believe also requires an updated mkfs
>>> from the integration repo.
>> Thanks for your response, however, even if I enlarged the image size to 2G,
>> still got no luck.
>> Per Zefan's comments, run 'btrfs device scan' fixed this issue.
> you should be able to achieve this via `device=` mount option(s?) as well:
>
> https://btrfs.wiki.kernel.org/index.php/Getting_started#Mount_Options
>
> ... for completeness :-) ... and posterity or whatever.
Nice, thanks for your sharing. 8-)
-Jeff
> C Anthony
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 6+ messages in thread
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2011-09-07 4:18 mount a multi-device filesystem using a loopback device Jeff Liu
2011-09-07 4:37 ` cwillu
2011-09-07 6:44 ` Jeff Liu
2011-09-08 5:32 ` C Anthony Risinger
2011-09-08 6:31 ` Jeff Liu
[not found] ` <4E670FB8.4000705@cn.fujitsu.com>
2011-09-07 6:42 ` Jeff Liu
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