Re: Any help to restore broken partition?

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

Hi,
-------- Original Message --------
Subject: Any help to restore broken partition?
From: Dmitriy Perlow <dap@open.by>
To: <linux-btrfs@vger.kernel.org>
Date: 2015年01月12日 03:59
> Hi to all!
>
> I've been using btrfs at my /home partition without any problems for 
> about
> 3 years but today it was made read only. I umounted it and executed 
> `btrfs
> check --repair` and got lots of errors.
Did you saved all the outputs of the btrfsck --repair?
>
> I run openSUSE 13.1 x64 with linux 3.11.10, Btrfs v3.18+20141230.
Kernel is somewhat old, but btrfs-progs is new enough for possible recovery.
>
> # btrfs fi show
> Label: none  uuid: 96e5c775-86b2-4dd9-a671-fe9a343cc10b
>             Total devices 1 FS bytes used 5.35GiB
>             devid    1 size 10.85GiB used 10.85GiB path /dev/sda3
Size seems small enough to do a full dd backup.
Better to do it in case btrfsck --repair makes things worse.
But it seems too late for your case.... it should be done before any 
'btrfs check --repair'

Also, you can use btrfs-image to do a backup, which should be much 
smaller than dd dump,
at the cost of no data dumped
(mainly used for dev purpose, like to check btrfsck works as expected or 
not,
and since it contains no data but only metadata, it should be somewhat 
OK to send it to developers)

If it's OK for you, it would be better to dump the driver with "-c9" 
option and send it to us for better test.

>
> # mount -o ro,recovery /home
> → no directories except of lost+found.
And what's inside that dir?
>
> # btrfs check /dev/sda3
> Checking filesystem on /dev/sda3
> UUID: 96e5c775-86b2-4dd9-a671-fe9a343cc10b
> checking extents
> Block Group[0, 4194304] existed.
> Block Group[4194304, 8388608] existed.
> Block Group[12582912, 8388608] existed.
> Block Group[20971520, 8388608] existed.
> Block Group[29360128, 1073741824] existed.
> Block Group[1103101952, 1073741824] existed.
> Block Group[2176843776, 1073741824] existed.
> Block Group[3250585600, 1073741824] existed.
> Block Group[4324327424, 1073741824] existed.
> Block Group[5398069248, 1073741824] existed.
> Block Group[6471811072, 1073741824] existed.
> Block Group[7545552896, 1073741824] existed.
> Block Group[8619294720, 1073741824] existed.
> Block Group[9693036544, 874512384] existed.
Seems only block group problems. --init-extent-tree may helps.
WARNING: Do it *AFTER* a full backup or do it on a btrfs-image restored 
backup!!
> Errors found in extent allocation tree or chunk allocation
> checking free space cache
> cache and super generation don't match, space cache will be invalidated
> checking fs roots
> checking csums
> checking root refs
Other things seems good.
Seems btrfsck --repair did the job, hoping your btrfs-progs has the 
patch to fix a bug that
may delete all the repaired files...

Thanks,
Qu
>
> found 36864 bytes used err is 0
> total csum bytes: 0
> total tree bytes: 20480
> total fs tree bytes: 8192
> total extent tree bytes: 4096
> btree space waste bytes: 15135
> file data blocks allocated: 0
>  referenced 0
>
>
> Any help please?
>