Btrfs devel - Sep 2012 - btrfs: open_ctree failed on external usb drive

Hi,

I have formated a previous ntfs partition to btrfs using gparted last
week. It''s an external usb drive.

I used it to backup another disk, then moving the datas back to the other disk.

I ran a crashplan backup and a couple of rsync of my home directory. I
moved back to this disk some data.

I''m running Debian Sid, 3.2.0-3-amd64 kernel and Btrfs v0.19
(0.19+20120328-8 according to dpkg), using XFCE4 and dolphin as a file
manager. The usb drive is auto-mounting, and I''m accessing it with
dolphin or console. I always use the "remove device safely" feature
from dolphin before disconnecting the drive or shutting down my
laptop.

Unfotunately, I can''t access anymore the drive :

75446.148236] usb 8-6: new high-speed USB device number 5 using ehci_hcd
[75446.281867] usb 8-6: New USB device found, idVendor=13fd, idProduct=1840
[75446.281877] usb 8-6: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[75446.281884] usb 8-6: Product: USB 2.0 Drive
[75446.281889] usb 8-6: Manufacturer: PI-239
[75446.281893] usb 8-6: SerialNumber: 533157464A39444233313232
[75446.282628] scsi9 : usb-storage 8-6:1.0
[75447.281188] scsi 9:0:0:0: Direct-Access     PI-239   USB 2.0 Drive
  1.08 PQ: 0 ANSI: 4
[75447.282934] sd 9:0:0:0: Attached scsi generic sg3 type 0
[75447.284169] sd 9:0:0:0: [sdc] 976773168 512-byte logical blocks:
(500 GB/465 GiB)
[75447.284728] sd 9:0:0:0: [sdc] Write Protect is off
[75447.284736] sd 9:0:0:0: [sdc] Mode Sense: 23 00 00 00
[75447.285345] sd 9:0:0:0: [sdc] No Caching mode page present
[75447.285352] sd 9:0:0:0: [sdc] Assuming drive cache: write through
[75447.288349] sd 9:0:0:0: [sdc] No Caching mode page present
[75447.288356] sd 9:0:0:0: [sdc] Assuming drive cache: write through
[75447.309900]  sdc: sdc1
[75447.312608] sd 9:0:0:0: [sdc] No Caching mode page present
[75447.312612] sd 9:0:0:0: [sdc] Assuming drive cache: write through
[75447.312615] sd 9:0:0:0: [sdc] Attached SCSI disk
[75447.624772] device label DD_SEB devid 1 transid 390 /dev/sdc1
[75447.626348] btrfs: disk space caching is enabled
[75447.666137] parent transid verify failed on 464265216 wanted 390 found 392
[75447.666146] parent transid verify failed on 464265216 wanted 390 found 392
[75447.666150] parent transid verify failed on 464265216 wanted 390 found 392
[75447.679199] btrfs: open_ctree failed

btrfsck shows lots or problems (see
https://dl.dropbox.com/u/747851/btrfsck.txt.gz 257K)

I''ve looked at my logfiles from thurday, and I didn''t see any
error
concerning btrfs.

So I have three questions :

1) did I do something wrong ?
2) is there a way to recover the data on this disk ?
3) is btrfs a good choice for an external usb drive ?

If you need more information, feel free to ask.

Regards,

Sebastien
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On Sun, Sep 16, 2012 at 03:24:53PM +0200, Sébastien Kalt
wrote:
> I''m running Debian Sid, 3.2.0-3-amd64 kernel and Btrfs v0.19
> (0.19+20120328-8 according to dpkg), using XFCE4 and dolphin as a file
> manager. The usb drive is auto-mounting, and I''m accessing it with
> dolphin or console. I always use the "remove device safely"
feature
> from dolphin before disconnecting the drive or shutting down my
> laptop.
What does the ''remove safely'' actually do?

eg.
sync, blockdev --flushbufs, echo 1 > /sys/block/sdX/device/delete ?
> [75447.624772] device label DD_SEB devid 1 transid 390 /dev/sdc1
> [75447.626348] btrfs: disk space caching is enabled
> [75447.666150] parent transid verify failed on 464265216 wanted 390 found
392
This has been fixed in 3.2 already, so it''s possible that some
blocks were not written in the way the filesystem expects.
> btrfsck shows lots or problems (see
> https://dl.dropbox.com/u/747851/btrfsck.txt.gz 257K)
> 
> I''ve looked at my logfiles from thurday, and I didn''t see
any error
> concerning btrfs.
ie. not caused by crash.
> So I have three questions :
> 
> 1) did I do something wrong ?
> 2) is there a way to recover the data on this disk ?
Data from a ''parent transid verify'' broken filesystem can be
retrieved
by Josef''s restore utility.
> 3) is btrfs a good choice for an external usb drive ?
If the drive unplugs unexpectedly, kernels < 3.4 do not handle this well.

david
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