Re: Linux-next regression?

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

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On 2018/11/26 下午11:01, Andrea Gelmini wrote:
> Hi everybody,
>    and thanks a lot for your work.
> 
>    I'm using BTRFS over LVM over cryptsetup, over Samsung SSD 860 EVO (latest git of btrfs-progs).
>    Usually I run kernel in development, because I know BTRFS is young and there are still lots of bugs and corner case to fix.
> 
>    Anyway, I just want to submit to you a - maybe - useful info.
> 
>    Yesterday I compiled and booted latest linux-next,¹ and I've got this:
> 
> -----------
> nov 26 01:18:22 glet kernel: Btrfs loaded, crc32c=crc32c-intel
> nov 26 01:18:22 glet kernel: BTRFS: device label home devid 1 transid 32759 /dev/mapper/cry-home
> nov 26 01:18:23 glet kernel: BTRFS info (device dm-3): force lzo compression, level 0
> nov 26 01:18:23 glet kernel: BTRFS info (device dm-3): disk space caching is enabled
> nov 26 01:18:23 glet kernel: BTRFS info (device dm-3): has skinny extents
> nov 26 01:18:23 glet kernel: BTRFS error (device dm-3): bad tree block start, want 2152002191360 have 8829432654847901262

This means we failed to read one extent tree block and caused the problem.

And if you're using default mkfs profile it should try again to use the
extra copy, but it doesn't look like to be the case.

BTW, does it always happen like this? Or is there any possibility involved?

> nov 26 01:18:23 glet kernel: BTRFS error (device dm-3): failed to read block groups: -5
> nov 26 01:18:23 glet kernel: BTRFS error (device dm-3): open_ctree failed
> -----------
> 
>    Now, rebooting with 4.19.0-041900 (downloaded from here)², or 4.20-rc4 (compiled on this machine), the problem disappears.
> 
>    Now, running scrub a few times, and copying data (all files of the logical volume) to external device, gives no complain
Would you please also try "btrfs check --readonly"?

> 
>    Here I stop. This is my primary dev laptop, and at the moment I can't spend time switching/rebooting/testing. I'm comparing the data with last backup (I rsync each hour), but it takes time (it's more then 3TB).
> 
>    So, that was about to let you know. Well, it's Ubuntu 18.10, and between reboots no dist-upgrade or changes in booting related packages or systemd.
> 
>   One question: I can completely trust the ok return status of scrub? I know is made for this, but shit happens...

No, scrub only checks csum of data and tree blocks, it doesn't ensure
the content of tree blocks are OK.

For comprehensive check, go "btrfs check --readonly".

However I don't think it's something "btrfs check --readonly" would
report, but some strange behavior, maybe from LVM or cryptsetup.

Thanks,
Qu

> 
> Kisses,
> Gelma   
> 
> -----------------
> ¹ commit:  8c9733fd9806c71e7f2313a280f98cb3051f93df
>   "Add linux-next specific files for 20181123"
> ² http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.19/
> 


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