Btrfs devel - Apr 2012 - segmentation fault while running btrfsck

Hi all,

    One of my btrfs volumes got corrupted, and seems to be
unrecoverable. When I tried to run a recent version of btrfsck (built
from git), it crashed with a segmentation fault. I have a file
containing the first 8 GB (copied with "dd if=/dev/sda5 ..."), which
seems to reproduce the segmentation fault when using the btrfsck tool.
The volume shouldn''t have any too-personal files (a different
partition handles "/home"), so I''m comfortable sharing it
with any
longstanding btrfs developers (yeah, "/etc/passwd", but ... whatever).
I have access to a machine on UC Berkeley''s network (w/ fast internet
access), so the 8GB shouldn''t be a problem. Also, here is the output
from btrfsck (the "** Segmentation Fault **" is my annotation -- I
think it''s printed by the shell according btrfsck''s error
code),
http://pastebin.com/3txgBn71 .

    I do need to use my computer, so I reformatted the partition with
ext4 after I couldn''t get my data back. I hope this error can help
development of BTRFS though; it seems like a very promising
filesystem. A final note: the corruption of my partition was likely
due to some hardware instability problems -- it could either be
related to the SATA controller (some of the earlier Intel H67 Sandy
Bridge motherboards like mine had issues), bad SATA cables, or new SSD
(though, I ran badblocks, and it seemed okay ... and very fast, yay!).
The disk would unmount, and wouldn''t be recognized by the motherboard
until I left the system off for a while.

Thanks,
Nicholas — https://ntung.com — 4432-nstung
--
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

On Wed, Apr 18, 2012 at 01:34:48AM -0700, Nicholas Tung
wrote:
>     One of my btrfs volumes got corrupted, and seems to be
> unrecoverable. When I tried to run a recent version of btrfsck (built
> from git), it crashed with a segmentation fault. I have a file
> containing the first 8 GB (copied with "dd if=/dev/sda5 ..."),
which
> seems to reproduce the segmentation fault when using the btrfsck tool.
> [...]
> http://pastebin.com/3txgBn71 .
I''ve seen the same error, caused probably same problems according to
what you write below. I had a raid1 (data/metadata) filesystem on top of
a few disks and added a new one. After a while of balance running I saw
tons of errors in syslog like

[ 3402.240402] sd 9:0:1:0: [sde] Unhandled error code
[ 3402.240404] sd 9:0:1:0: [sde]  Result: hostbyte=DID_BAD_TARGET
driverbyte=DRIVER_OK
[ 3402.240406] sd 9:0:1:0: [sde] CDB: Read(10): 28 00 06 6e 59 40 00 00 08 00
[ 3402.240409] end_request: I/O error, dev sde, sector 107895104

I had to reboot the machine, and after running fsck I saw messages like
in your log:

Check tree block failed, want=2327687168, have=0

where the ''want'' sector numbers matched the ones from syslog.
And after
a while segfault. I was more interested to see how scrub and automatic
repair would work, so I did not dig deeper. (Yeah, scrub repaired the
blocks and I was able to remove the device from the set again.)

Looking to your logs again,

parent transid verify failed on 2327711744 wanted 2488 found 464

I did not see any of these in my fsck output, guessing from the
wanted/found numbers, it''s a lost write on the device.

* What kernel did you run at that time? (3.2 or older)
* How many disks and what raid profile did you use?

[...]
> A final note: the corruption of my partition was likely
> due to some hardware instability problems -- it could either be
> related to the SATA controller (some of the earlier Intel H67 Sandy
> Bridge motherboards like mine had issues), bad SATA cables, or new SSD
> (though, I ran badblocks, and it seemed okay ... and very fast, yay!).
> The disk would unmount, and wouldn''t be recognized by the
motherboard
> until I left the system off for a while.
I''m blaming the SATA port/cable combo on my side, two different disks
exhibited the same problems there, while ok in another.


thanks,
david
--
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