[help] bad csum and magic on both superblocks

[Tristan Plumb <wild.rugosa@gmail.com>]

I had two nvme drives set up with raid1 metadata and rai0 data. One of
them failed, as far as I
can tell it shorted the 3.3v rail to ground, but the other is mostly
fine. However, neither of the two
superblocks have correct checksums or magic, though they appear to be
practically identical.

None of the tools that I've tried to use so far, other than
inspect-internal dump-super, have
provided an option to skip the superblock checksum and magic test, so
I get results like:

[root@ping:~]# btrfs restore -l -i /dev/nvme1n1p2
No valid Btrfs found on /dev/nvme1n1p2
Could not open root, trying backup super
ERROR: superblock checksum mismatch
No valid Btrfs found on /dev/nvme1n1p2
Could not open root, trying backup super
ERROR: superblock bytenr 274877906944 is larger than device size 190805180416
Could not open root, trying backup super

The other contents of the superblock looks fairly reasonable however.
Would people
recommend that I add an option to ignore the checksum/magic errors
(which is my inclination),
or that I repair the superblock manually somehow? Or (and my real
reason for bothering you all)
is there another option/approach that someone would suggest?

Cheers,
Tristan

[root@ping:~]# uname -a; btrfs --version
Linux ping 5.4.59 #1-NixOS SMP Wed Aug 19 06:16:29 UTC 2020 x86_64 GNU/Linux
btrfs-progs v5.7

[root@ping:~]# btrfs inspect-internal dump-super -s 0 --force /dev/nvme1n1p2
superblock: bytenr=65536, device=/dev/nvme1n1p2
---------------------------------------------------------
csum_type 0 (crc32c)
csum_size 4
csum 0x344a5afc [DON'T MATCH]
bytenr 65536
flags 0x1
( WRITTEN )
magic ........ [DON'T MATCH]
fsid badf716b-44c3-42a5-af84-bb91fccf0f47
metadata_uuid badf716b-44c3-42a5-af84-bb91fccf0f47
label
generation 730413
root 914966282240
sys_array_size 97
chunk_root_generation 730413
root_level 1
chunk_root 912808476672
chunk_root_level 1
log_root 0
log_root_transid 0
log_root_level 0
total_bytes 2171858845696
bytes_used 369171148800
sectorsize 4096
nodesize 16384
leafsize (deprecated) 16384
stripesize 4096
root_dir 6
num_devices 2
compat_flags 0x0
compat_ro_flags 0x0
incompat_flags 0x161
( MIXED_BACKREF |
  BIG_METADATA |
  EXTENDED_IREF |
  SKINNY_METADATA )
cache_generation 730413
uuid_tree_generation 730413
dev_item.uuid a792e7c4-88a8-4e2e-9d68-39baa50b6d0d
dev_item.fsid badf716b-44c3-42a5-af84-bb91fccf0f47 [match]
dev_item.type 0
dev_item.total_bytes 190805180416
dev_item.bytes_used 4328521728
dev_item.io_align 4096
dev_item.io_width 4096
dev_item.sector_size 4096
dev_item.devid 1
dev_item.dev_group 0
dev_item.seek_speed 0
dev_item.bandwidth 0
dev_item.generation 0

[root@ping:~]# btrfs inspect-internal dump-super -s 1 --force /dev/nvme1n1p2
superblock: bytenr=67108864, device=/dev/nvme1n1p2
---------------------------------------------------------
csum_type 0 (crc32c)
csum_size 4
csum 0x942b7232 [DON'T MATCH]
bytenr 67108864
flags 0x1
( WRITTEN )
magic ........ [DON'T MATCH]
fsid badf716b-44c3-42a5-af84-bb91fccf0f47
metadata_uuid badf716b-44c3-42a5-af84-bb91fccf0f47
label
generation 730413
root 914966282240
sys_array_size 97
chunk_root_generation 730413
root_level 1
chunk_root 912808476672
chunk_root_level 1
log_root 0
log_root_transid 0
log_root_level 0
total_bytes 2171858845696
bytes_used 369171148800
sectorsize 4096
nodesize 16384
leafsize (deprecated) 16384
stripesize 4096
root_dir 6
num_devices 2
compat_flags 0x0
compat_ro_flags 0x0
incompat_flags 0x161
( MIXED_BACKREF |
  BIG_METADATA |
  EXTENDED_IREF |
  SKINNY_METADATA )
cache_generation 730413
uuid_tree_generation 730413
dev_item.uuid a792e7c4-88a8-4e2e-9d68-39baa50b6d0d
dev_item.fsid badf716b-44c3-42a5-af84-bb91fccf0f47 [match]
dev_item.type 0
dev_item.total_bytes 190805180416
dev_item.bytes_used 4328521728
dev_item.io_align 4096
dev_item.io_width 4096
dev_item.sector_size 4096
dev_item.devid 1
dev_item.dev_group 0
dev_item.seek_speed 0
dev_item.bandwidth 0
dev_item.generation 0