Re: bad file extent, some csum missing - how to check that restored volumes are error-free?

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

On 2021/7/15 上午1:53, Dave T wrote:
> I was running btrfs send | receive to a target host via ssh and the
> operation suddenly failed in the middle.
>
> I ran this check:
>
> btrfs check /dev/mapper/${xyz}
>
> This shows lots of these errors:
>    root 329 inode 262 errors 1040, bad file extent, some csum missing

Normally this is a minor error, normally caused by older kernels.

The original mode did a very bad report format.

You may want to run "btrfs check --mode=lowmem" to get a more human
readable report.
 From that we can get a full view of the problem and give better advice.

Thanks,
Qu

>    root 329 inode 7070 errors 1040, bad file extent, some csum missing
>    root 329 inode 7242 errors 1040, bad file extent, some csum missing
>    root 329 inode 7246 errors 1040, bad file extent, some csum missing
>    root 329 inode 7252 errors 1040, bad file extent, some csum missing
>    root 329 inode 7401 errors 1040, bad file extent, some csum missing
>    root 329 inode 7753 errors 1040, bad file extent, some csum missing
>    root 330 inode 588 errors 1040, bad file extent, some csum missing
>    root 334 inode 258 errors 1040, bad file extent, some csum missing
>    root 334 inode 636 errors 1040, bad file extent, some csum missing
>    root 334 inode 3151 errors 1040, bad file extent, some csum missing
>    ...
>    root 334 inode 184871 errors 1040, bad file extent, some csum missing
>    root 334 inode 184872 errors 1040, bad file extent, some csum missing
>    root 334 inode 184874 errors 1040, bad file extent, some csum missing
>
> I rebooted without any problems, then connected an external USB HDD.
> Then I created new snapshots and used btrfs send | receive to send
> them to the USB HDD.
>
> Next I installed a new SSD and restored the snapshots. Then I ran
> "btrfs check --check-data-csum /dev/mapper/abc" on the new device. It
> shows:
>
> Opening filesystem to check...
> Checking filesystem on /dev/mapper/abc
> UUID: fac54a70-8c27-4cbe-a8d0-325e761ba01d
> [1/7] checking root items
> [2/7] checking extents
> [3/7] checking free space cache
> [4/7] checking fs roots
> [5/7] checking csums against data
> [6/7] checking root refs
> [7/7] checking quota groups skipped (not enabled on this FS)
> found 128390598656 bytes used, no error found
> total csum bytes: 124046564
> total tree bytes: 1335197696
> total fs tree bytes: 1140211712
> total extent tree bytes: 50757632
> btree space waste bytes: 168388261
> file data blocks allocated: 127058169856
>   referenced 142833545216
>
> What else can or should I do to be sure my restored snapshots are error-free?
> What additional checks would you recommend on the new device?
> The new device is a Samsung EVO 970 Plus.
> The old device was a Samsung 950 Pro.
>