Re: OFF-By-One Trouble? [BTRFS in Debian Stretch Kernel 4.9.0-4-amd64]

[ein <ein.net@gmail.com>]

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On 12/12/2017 11:22 AM, Juergen Sauer wrote:
> Hi collegues,

Hello.

> 
> this morning we've got a problm with btrfs in Debian Stable.
> 
> Yesterday we had our fs filled below 30% space usage. No further 
> usage came in the usage is nearly the same, but ...
> 
> # df -h . Dateisystem    Größe Benutzt Verf. Verw% Eingehängt auf 
> /dev/vdb1      483G    483G  148K  100% /mnt
> 
> # btrfs fi df . Data, single: total=480.97GiB, used=480.97GiB 
> System, single: total=32.00MiB, used=96.00KiB Metadata, single: 
> total=2.00GiB, used=1.29GiB GlobalReserve, single:
> total=512.00MiB, used=0.00B
> 
> # btrfs fi show . Label: 'AXSDaten'  uuid: 
> fde7e31f-4127-4a9d-b7c6-774ceff8f7c1 Total devices 1 FS bytes used 
> 482.26GiB devid    1 size 483.00GiB used 483.00GiB path /dev/vdb1
> 
> # btrfs --version btrfs-progs v4.7.3
> 
> we found exerpt of kernel log: [  199.391577] attempt to access 
> beyond end of device [  199.391598] vdb1: rw=536870984, 
> want=1012922336, limit=1012922335 [  199.391615] BTRFS error 
> (device vdb1): bdev /dev/vdb1 errs: wr 301, rd 0, flush 0, corrupt 
> 0, gen 0 r If I interpret the log right, on the FS the kernel
> wants to write on block  1012922336, but the fs was created with
> max 1012922335 blocks.
> 
> Looks to us here like a typical off-by-one error on accessing the 
> last block of device.

Or user error, or HW problems, I use Debian 9 in production and I
completed multiple BTRFS resizes with success. The only one difference I
see for now is:
server #1:
root@node0:~# uname -a; btrfs
- --version



Linux node0 4.12.0-0.bpo.2-amd64 #1 SMP Debian 4.12.13-1~bpo9+1
(2017-09-28) x86_64
GNU/Linux


btrfs-progs v4.13.3

server #2:
root@node0.intranet.xxx.pl:~# uname -a; btrfs --version
Linux node0.intranet.xxx.pl 4.12.0-0.bpo.2-amd64 #1 SMP Debian
4.12.13-1~bpo9+1 (2017-09-28) x86_64 GNU/Linux
btrfs-progs v4.13.3

Both kernels and btrfs-progs were from backports.

> This error was repeating under ff. conditions: - shutdown the 
> virtual server (kvm), - extend the physical file of the according 
> virtual hdd by 20% (from 483 Gib to 520 GiB)

Extend exactly how?

> - restart virtual server - fixed partion size (parted), mounted - 
> called btrfs fi resize max on the corresponding mount point
> 
> Error came back, nearly at once.
> 
> Any other Idea to fix this error?
> 
> mit freundlichen Grüßen Jürgen Sauer
> 
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