Re: Problem with Btrsf

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

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On 2020/12/2 上午2:48, Régis Priqueler wrote:
> Hi,
> 
> My system is an synology with a SHR array of 3 2Tb WD Red (WD40EFAX)
> whish seems to be a SMR .
> 
> The filesystem has gone to read only this afternoon (without any
> modification of the NAS).
> 
> Synology says that the disks are not compatible because of SMR.
> 
> As I wanted to be sure I browse the logs and found that there's some errors
> 
> In dmesg
> 
> some BTRFS critical (device dm-0): leaf bad key order,
> block=2717818945536, root=2, slot=41

That's the root cause, extent tree has something corrupted.

Normally if you're using newer enough kernel, such problem should not
reach disk at least.

The vendor kernel is pretty old, 4.4, and I'm not sure how heavily the
backport is.

> 
> then
> 
> 2020-12-01T13:50:28+01:00 MediasHomeBase kernel: [5372093.750621] BTRFS:
> error (device dm-0) in btrfs_start_dirty_block_groups:4004: errno=-5 IO
> failure
> 2020-12-01T13:50:28+01:00 MediasHomeBase kernel: [5372093.766864] BTRFS
> warning (device dm-0): Skipping commit of aborted transaction.
> 2020-12-01T13:50:28+01:00 MediasHomeBase kernel: [5372093.775340] BTRFS:
> error (device dm-0) in cleanup_transaction:2032: errno=-5 IO failure
> 2020-12-01T14:50:35+01:00 MediasHomeBase kernel: [5375701.176237]
> nr_pdflush_threads exported in /proc is scheduled for removal
> 
> I'm not very familliar with BTRFS
> 
> Is there a way to repair this problem ?

Btrfs check output please.

Please try the latest btrfs-progs.

At the meantime, the corruption is only limited to extent tree, thus you
still have a chance to mount the fs RO, and salvage your data.

Thanks,
Qu

> 
> Best regards,
> 
> Infos:
> 
> Linux MediasHomeBase 4.4.59+ #25426 SMP PREEMPT Wed Jul 8 03:21:29 CST
> 2020 x86_64 GNU/Linux synology_apollolake_1019+
> btrfs-progs v4.0
> Label: '2020.09.17-15:40:50 v25426'  uuid:
> aae48b56-d453-4dfb-b5dd-3af62e923686
>     Total devices 1 FS bytes used 2.22TiB
>     devid    1 size 7.27TiB used 2.52TiB path /dev/mapper/vg1000-lv
> 
> Data, single: total=2.46TiB, used=2.22TiB
> System, DUP: total=8.00MiB, used=64.00KiB
> Metadata, DUP: total=28.50GiB, used=2.64GiB
> GlobalReserve, single: total=2.00GiB, used=0.00B
> 


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