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From: Illia Bobyr <>
To: Qu Wenruo <>,
Subject: Re: "parent transid verify failed" and mount usebackuproot does not seem to work
Date: Wed, 1 Jul 2020 14:36:59 -0700
Message-ID: <> (raw)
In-Reply-To: <>

On 7/1/2020 3:48 AM, Qu Wenruo wrote:
> On 2020/7/1 下午6:16, Illia Bobyr wrote:
>> On 6/30/2020 6:36 PM, Qu Wenruo wrote:
>>> On 2020/7/1 上午3:41, Illia Bobyr wrote:
>>>> [...]
>>> Looks like some tree blocks not written back correctly.
>>> Considering we don't have known write back related bugs with 5.6, I
>>> guess bcache may be involved again?
>> A bit more details: the system started to misbehave.
>> Interactive session was saying that the main file system became read/only.
> Any dmesg of that RO event?
> That would be the most valuable info to help us to locate the bug and
> fix it.
> I guess there is something wrong before that, and by somehow it
> corrupted the extent tree, breaking the life keeping COW of metadata and
> screwed up everything.

After I will restore the data, I will check the kernel log to see if
there are any messages in there.
Will post here if I will find anything.

>> [...]
>>> In this case, I guess "btrfs ins dump-super -fFa" output would help to
>>> show if it's possible to recover.
>> Here is the output:
> OK, the backup root is fine.
> So this means, metadata COW is corrupted, which caused the transid mismatch.
>>> Anyway, something looks strange.
>>> The backup roots have a newer generation while the super block is still
>>> old doesn't look correct at all.
>> Just in case, here is the output of "btrfs check", as suggested by "A L
>> <>".  It does not seem to contain any new information.
>> parent transid verify failed on 16984014372864 wanted 138350 found 131117
>> parent transid verify failed on 16984014405632 wanted 138350 found 131127
>> parent transid verify failed on 16984013406208 wanted 138350 found 131112
>> parent transid verify failed on 16984075436032 wanted 138384 found 131136
>> parent transid verify failed on 16984075436032 wanted 138384 found 131136
>> parent transid verify failed on 16984075436032 wanted 138384 found 131136
>> Ignoring transid failure
>> ERROR: child eb corrupted: parent bytenr=16984175853568 item=8 parent
>> level=2 child level=0
>> ERROR: failed to read block groups: Input/output error
> Extent tree is completely screwed up, no wonder the transid error happens.
> I don't believe it's reasonable possible to restore the fs to RW status.
> The only remaining method left is btrfs-restore then.

There are no more available SATA connections in the system and there is
a lot of data in that FS (~7TB).
I do not immediately have another disk that would be able to hold this much.

At the same time this FS is RAID0.
I wonder if there is a way to first check if restore will work should I
will disconnect half of the disks, as each half contains all the data.
And then if it does, I would be able to restore by reusing the space on
of the mirrors.

I see "-D: Dry run" that can be passed to "btrfs restore", but, I guess,
it would not really do a full check of the data, making sure that the
restore would really succeed, does it?

Is there a way to perform this kind of check?
Or is "btrfs restore" the only option at the moment?

  reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-30 19:41 Illia Bobyr
2020-07-01  1:36 ` Qu Wenruo
2020-07-01 10:16   ` Illia Bobyr
2020-07-01 10:48     ` Qu Wenruo
2020-07-01 21:36       ` Illia Bobyr [this message]
2020-07-01 23:50         ` Qu Wenruo
  -- strict thread matches above, loose matches on Subject: below --
2020-06-30 19:26 Illia Bobyr
2020-06-30 19:55 ` Lukas Straub
2020-06-30  4:24 Illia Bobyr

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