Re: parent transid verify failed on raid1

[Qu Wenruo <wqu@suse.com>]

在 2025/5/8 02:03, Ivo Smits 写道:
> Hello everyone,
> 
> After some abuse (drive going offline and unexpected shutdowns) one of 
> my fairly large BTRFS filesystems seems to suffer from some corruption. 
> The filesystem still mounts and operates mostly fine. A lot of errors 
> (probably caused by a drive going offline and later returning) have been 
> recovered from a good RAID1 mirror by scrub a little while ago, but some 
> problems persist.
> 
> The kernel log is repeating the following two messages about every 30 
> seconds:
> 
> BTRFS error (device sdg1): parent transid verify failed on logical 
> 31419461632000 mirror 1 wanted 1240926 found 1089963
> BTRFS error (device sdg1): parent transid verify failed on logical 
> 31419461632000 mirror 2 wanted 1240926 found 1089963

The transid mismatch mostly a death sentence for a btrfs.

This normally means bad metadata COW or bad hardware FLUSH/FUA behavior.

> 
> I suspect this might be some background process in the kernel trying to 
> clean things up since it starts after mounting and doesn't stop.

Nope, no regular operation should lead to such problem.

Not to mention both mirrors share the same bad transid.

[...]
> 
> I also ran btrfs check while the filesystem was unmounted. This first 
> discovered the two transid failures also found by scrub, and then 
> continued to find a lot more errors, like reference count and bytenr 
> mismatches. Since the filesystem appears to operate normally and scrub 
> did not find those errors, could this just be blocks which are no longer 
> part of the filesystem tree, possibly not even referenced by anything?

When anything go wrong on btrfs, please just go "btrfs check --readonly" 
on the unmounted fs directly.

That's the only reliable way to evaluate the problem.
If the fs is too large, or you want a better way to show the errors, 
"btrfs check --readonly --mode=lowmem" will also help.

> 
> Is this situation something btrfs check can fix? Is it possible to only 
> let it fix the most problematic transid error and ignore everything 
> else? Could manually patching the transid value help btrfs clean things up?

Normally no to all the questions above.

Thanks,
Qu

> 
> Most of the data on the filesystem is backup data, or can be backed up 
> elsewhere, so losing some files would not be the end of the world, as 
> long as damaged files can be identified and there is no silent data 
> corruption.
> 
> Best regards,
> 
> Ivo
> 
>