btrfs raid1 degraded does not mount or fsck

btrfs raid1 degraded does not mount or fsck

[Vladi Gergov]

kernel: scratch git repo from today 10.29.10 @ 14:30 PST
Btrfs v0.19-35-g1b444cd-dirty

>>> gypsyops @ /mnt > sudo btrfs filesystem show
Label: 'das4'  uuid: d0e5137f-e5e7-49da-91f6-a9c4e4e72c6f
    Total devices 3 FS bytes used 1.38TB
    devid    3 size 1.82TB used 0.00 path /dev/sdb
    devid    2 size 1.82TB used 1.38TB path /dev/sdc
    *** Some devices missing

Btrfs v0.19-35-g1b444cd-dirty

>>> gypsyops @ /mnt > sudo mount -o degraded /dev/sdc das3/
Password: 
mount: wrong fs type, bad option, bad superblock on /dev/sdc,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

[  684.577540] device label das4 devid 2 transid 107954 /dev/sdc
[  684.595150] btrfs: allowing degraded mounts
[  684.595594] btrfs: failed to read chunk root on sdb
[  684.604110] btrfs: open_ctree failed

>>> gypsyops @ /mnt > sudo btrfsck /dev/sdc
btrfsck: volumes.c:1367: btrfs_read_sys_array: Assertion `!(ret)' failed.

any help please?

-- 

,-| Vladi
`-| Gergov

!DSPAM:4ccb39a9191821603519226!

Re: btrfs raid1 degraded does not mount or fsck

[Goffredo Baroncelli]

On Friday, 29 October, 2010, Vladi Gergov wrote:
> kernel: scratch git repo from today 10.29.10 @ 14:30 PST
> Btrfs v0.19-35-g1b444cd-dirty
> 
> >>> gypsyops @ /mnt > sudo btrfs filesystem show
> Label: 'das4'  uuid: d0e5137f-e5e7-49da-91f6-a9c4e4e72c6f
>     Total devices 3 FS bytes used 1.38TB
>     devid    3 size 1.82TB used 0.00 path /dev/sdb
>     devid    2 size 1.82TB used 1.38TB path /dev/sdc
>     *** Some devices missing
> 
> Btrfs v0.19-35-g1b444cd-dirty
> 
> >>> gypsyops @ /mnt > sudo mount -o degraded /dev/sdc das3/
> Password: 
> mount: wrong fs type, bad option, bad superblock on /dev/sdc,
>        missing codepage or helper program, or other error
>        In some cases useful info is found in syslog - try
>        dmesg | tail  or so
> 
> [  684.577540] device label das4 devid 2 transid 107954 /dev/sdc
> [  684.595150] btrfs: allowing degraded mounts
> [  684.595594] btrfs: failed to read chunk root on sdb
> [  684.604110] btrfs: open_ctree failed
> 
> >>> gypsyops @ /mnt > sudo btrfsck /dev/sdc
> btrfsck: volumes.c:1367: btrfs_read_sys_array: Assertion `!(ret)' failed.
> 
> any help please?

did you execute 

	btrfs dev scan

before trying to mount the filesystem ?

> -- 
> 
> ,-| Vladi
> `-| Gergov
> 
> !DSPAM:4ccb39a9191821603519226!
> 
> 
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Re: btrfs raid1 degraded does not mount or fsck

[Chris Mason]

Excerpts from Vladi Gergov's message of 2010-10-29 16:53:42 -0400:
> >>> gypsyops @ /mnt > sudo mount -o degraded /dev/sdc das3/
> Password: 
> mount: wrong fs type, bad option, bad superblock on /dev/sdc,
>        missing codepage or helper program, or other error
>        In some cases useful info is found in syslog - try
>        dmesg | tail  or so
> 
> [  684.577540] device label das4 devid 2 transid 107954 /dev/sdc
> [  684.595150] btrfs: allowing degraded mounts
> [  684.595594] btrfs: failed to read chunk root on sdb
> [  684.604110] btrfs: open_ctree failed
> 
> >>> gypsyops @ /mnt > sudo btrfsck /dev/sdc
> btrfsck: volumes.c:1367: btrfs_read_sys_array: Assertion `!(ret)' failed.

Ok, I dug through this and found the bug responsible for your
unmountable FS.  When we're mounted in degraded mode, and we don't have
enough drives available to do raid1,10, we're can use the wrong raid
level for new allocations.

I'm fixing the kernel side so this doesn't happen anymore, but I'll need
to rebuild the chunk tree (and probably a few others) off your good disk to
fix things.

I've got it reproduced here though, so I'll make an fsck that can scan
for the correct trees and fix it for you.

Since you're basically going to be my first external fsck customer, is
there anyway you can do a raw device based backup of the blocks?  This
way if I do mess things up we can repeat the experiment.

-chris

Re: btrfs raid1 degraded does not mount or fsck

[Larry Reaves]

Chris Mason <chris.mason <at> oracle.com> writes:

> 
> Excerpts from Vladi Gergov's message of 2010-10-29 16:53:42 -0400:
> > >>> gypsyops @ /mnt > sudo mount -o degraded /dev/sdc das3/
> > Password: 
> > mount: wrong fs type, bad option, bad superblock on /dev/sdc,
> >        missing codepage or helper program, or other error
> >        In some cases useful info is found in syslog - try
> >        dmesg | tail  or so
> > 
> > [  684.577540] device label das4 devid 2 transid 107954 /dev/sdc
> > [  684.595150] btrfs: allowing degraded mounts
> > [  684.595594] btrfs: failed to read chunk root on sdb
> > [  684.604110] btrfs: open_ctree failed
> > 
> > >>> gypsyops @ /mnt > sudo btrfsck /dev/sdc
> > btrfsck: volumes.c:1367: btrfs_read_sys_array: Assertion `!(ret)' failed.
> 
> Ok, I dug through this and found the bug responsible for your
> unmountable FS.  When we're mounted in degraded mode, and we don't have
> enough drives available to do raid1,10, we're can use the wrong raid
> level for new allocations.
> 
> I'm fixing the kernel side so this doesn't happen anymore, but I'll need
> to rebuild the chunk tree (and probably a few others) off your good disk to
> fix things.
> 
> I've got it reproduced here though, so I'll make an fsck that can scan
> for the correct trees and fix it for you.
> 
> Since you're basically going to be my first external fsck customer, is
> there anyway you can do a raw device based backup of the blocks?  This
> way if I do mess things up we can repeat the experiment.
> 
> -chris

I'm seeing this same error, uname -a shows:
2.6.38-11-generic
although, my fs went down a month or so ago so it could have been a slightly
earlier Ubuntu kernel.  Is this the same issue?  Is that very targeted fsck
available somewhere?  I've got my replacement disk ready to add, I just need to
get the other 3 mounted.  Data and metadata are both raid10.  I really need to
start tracking the kernel again :(.  Thanks for any help.

-Larry

btrfs raid1 degraded in need of chuck tree rebuild

[Vladi Gergov]

Below is my original post about my fs. Just wondering if anyone knows if
I can at this point get my data back or cut my losses. Is an fsck cable
of getting this fixed close or has my 2 year wait been in vain. Thanks
in advance!

Excerpts from Vladi Gergov's message of 2010-10-29 16:53:42 -0400:
> >>> gypsyops @ /mnt > sudo mount -o degraded /dev/sdc das3/
> Password: 
> mount: wrong fs type, bad option, bad superblock on /dev/sdc,
>        missing codepage or helper program, or other error
>        In some cases useful info is found in syslog - try
>        dmesg | tail  or so
> 
> [  684.577540] device label das4 devid 2 transid 107954 /dev/sdc
> [  684.595150] btrfs: allowing degraded mounts
> [  684.595594] btrfs: failed to read chunk root on sdb
> [  684.604110] btrfs: open_ctree failed
> 
> >>> gypsyops @ /mnt > sudo btrfsck /dev/sdc
> btrfsck: volumes.c:1367: btrfs_read_sys_array: Assertion `!(ret)'
> failed.

Ok, I dug through this and found the bug responsible for your
unmountable FS.  When we're mounted in degraded mode, and we don't have
enough drives available to do raid1,10, we're can use the wrong raid
level for new allocations.

I'm fixing the kernel side so this doesn't happen anymore, but I'll need
to rebuild the chunk tree (and probably a few others) off your good disk
to
fix things.

I've got it reproduced here though, so I'll make an fsck that can scan
for the correct trees and fix it for you.

Since you're basically going to be my first external fsck customer, is
there anyway you can do a raw device based backup of the blocks?  This
way if I do mess things up we can repeat the experiment.

-chris

-- 

,-| Vladi
`-| Gergov