On Sun, Mar 21, 2021 at 2:03 PM Chris Murphy [off-list ref] wrote:

On Sat, Mar 20, 2021 at 11:54 PM Dave T [off-list ref] wrote:

quoted

# btrfs check -r 2853787942912 /dev/mapper/xyz
Opening filesystem to check...
parent transid verify failed on 2853787942912 wanted 29436 found 29433
parent transid verify failed on 2853787942912 wanted 29436 found 29433
parent transid verify failed on 2853787942912 wanted 29436 found 29433
Ignoring transid failure
parent transid verify failed on 2853827723264 wanted 29433 found 29435
parent transid verify failed on 2853827723264 wanted 29433 found 29435
parent transid verify failed on 2853827723264 wanted 29433 found 29435
Ignoring transid failure
leaf parent key incorrect 2853827723264
ERROR: could not setup extent tree
ERROR: cannot open file system

btrfs insp dump-t -t 2853827723264 /dev/

# btrfs insp dump-t -t 2853827723264 /dev/mapper/xzy
btrfs-progs v5.11
parent transid verify failed on 2853827608576 wanted 29436 found 29433
parent transid verify failed on 2853827608576 wanted 29436 found 29433
parent transid verify failed on 2853827608576 wanted 29436 found 29433
Ignoring transid failure
leaf parent key incorrect 2853827608576
WARNING: could not setup extent tree, skipping it
parent transid verify failed on 2853827608576 wanted 29436 found 29433
Ignoring transid failure
leaf parent key incorrect 2853827608576
Couldn't setup device tree
ERROR: unable to open /dev/mapper/xzy

# btrfs insp dump-t -t 2853787942912 /dev/mapper/xzy
btrfs-progs v5.11
parent transid verify failed on 2853827608576 wanted 29436 found 29433
parent transid verify failed on 2853827608576 wanted 29436 found 29433
parent transid verify failed on 2853827608576 wanted 29436 found 29433
Ignoring transid failure
leaf parent key incorrect 2853827608576
WARNING: could not setup extent tree, skipping it
parent transid verify failed on 2853827608576 wanted 29436 found 29433
Ignoring transid failure
leaf parent key incorrect 2853827608576
Couldn't setup device tree
ERROR: unable to open /dev/mapper/xzy

# btrfs insp dump-t -t 2853827608576 /dev/mapper/xzy
btrfs-progs v5.11
parent transid verify failed on 2853827608576 wanted 29436 found 29433
parent transid verify failed on 2853827608576 wanted 29436 found 29433
parent transid verify failed on 2853827608576 wanted 29436 found 29433
Ignoring transid failure
leaf parent key incorrect 2853827608576
WARNING: could not setup extent tree, skipping it
parent transid verify failed on 2853827608576 wanted 29436 found 29433
Ignoring transid failure
leaf parent key incorrect 2853827608576
Couldn't setup device tree
ERROR: unable to open /dev/mapper/xzy

quoted

It appears the backup root is already stale.

I'm not sure. If you can post the contents of that leaf (I don't think
it will contain filenames but double check) Qu might have an idea if
it's safe to try a read-write mount with -o usebackuproot without
causing problems later.

quoted

quoted

What you eventually need to look at is what precipitated the transid
failures, and avoid it.

The USB drive was disconnected by the user (an accident). I have other
devices with the same hardware that have never experienced this issue.

Do you have further ideas or suggestions I can try? Thank you for your
time and for sharing your expertise.

The drive could be getting write ordering wrong all the time, and it
only turns into a problem with a crash, power fail, or accidental
disconnect.  More common is the write ordering is only sometimes
wrong, and a crash or powerfail is usually survivable, but leads to a
false sense of security about the drive.

The simple theory of write order is data->metadata->sync->super->sync.
It shouldn't ever be the case that a newer superblock generation is on
stable media before the metadata it points to.

The drive is a Western Digital Elements 5TB. I searched a bit on write
order under Linux, but I did not find any helpful articles regarding
any configuration changes I could make. Is this purely a hardware
issue, or are there steps I can take to ensure the correct write
ordering?

Thank you!