Re: Help requested: btrfs can't read superblock

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

在 2024/3/19 07:52, kind.moon1862@fastmail.com 写道:
>
> Dear btrfs team,
>
> I've been asked to help someone with a btrfs problem.  They use CentOS 7.  I've been told the host was shut down cleanly, but it won't mount a btrfs filesystem when powering on.
>
> Below is what I've done so far.  Any guidance would be appreciated!
>
> I booted using SystemRescue 11.0.  Some info about the rescue OS:
>
> # uname -a
> Linux sysrescue 6.6.14-1-lts #1 SMP PREEMPT_DYNAMIC Fri, 26 Jan 2024 11:54:58 +0000 x86_64 GNU/Linux
>
> # btrfs --version
> btrfs-progs v6.6.3
>
> Here are the disks:
>
> # btrfs fi show
> Label: '<redacted>'  uuid: 834b4bfd-fbd4-40b9-8868-d1187c3c5a63
> 	Total devices 4 FS bytes used 17.44TiB
> 	devid    1 size 9.10TiB used 8.94TiB path /dev/sda
> 	devid    2 size 9.10TiB used 8.94TiB path /dev/sdb
> 	devid    3 size 9.10TiB used 8.94TiB path /dev/sdc
> 	devid    4 size 9.10TiB used 8.94TiB path /dev/sdd
>
> I tried mounting:
>
> # mount -t btrfs -o recovery,ro /dev/sda /mnt/data
> mount: /mnt/data: can't read superblock on /dev/sda.
>         dmesg(1) may have more information after failed mount system call.

Use "mount -o rescue=all,ro" instead.

>
> dmesg shows this:
>
> [ 1940.962632] BTRFS info (device sda): first mount of filesystem 834b4bfd-fbd4-40b9-8868-d1187c3c5a63
> [ 1940.962665] BTRFS info (device sda): using crc32c (crc32c-intel) checksum algorithm
> [ 1940.962686] BTRFS warning (device sda): 'recovery' is deprecated, use 'rescue=usebackuproot' instead
> [ 1940.962692] BTRFS info (device sda): trying to use backup root at mount time
> [ 1940.962698] BTRFS info (device sda): disk space caching is enabled
> [ 1942.115796] BTRFS critical (device sda): corrupt leaf: root=2 block=11438351450112 slot=170, invalid key objectid, have 5822947745796 expect to be aligned to 4096

Bad extent item start bytenr, 5822947745796 = 0x54bc2bb6004, the last
0x004 looks like a bitflip.

Please run memtest to make sure your hardware memory is fine, or such
problem would just happen again and again.

Thankfully extent tree corruption is not a big deal for "rescue=all,ro"
mount.

Thanks,
Qu

> [ 1942.115819] BTRFS error (device sda): read time tree block corruption detected on logical 11438351450112 mirror 2
> [ 1942.116170] BTRFS critical (device sda): corrupt leaf: root=2 block=11438351450112 slot=170, invalid key objectid, have 5822947745796 expect to be aligned to 4096
> [ 1942.116183] BTRFS error (device sda): read time tree block corruption detected on logical 11438351450112 mirror 1
> [ 1942.116212] BTRFS error (device sda): failed to read block groups: -5
> [ 1942.140369] BTRFS error (device sda): open_ctree failed
>
> I tried to recover the superblock:
>
> # btrfs rescue super-recover -v /dev/sda
>
> All Devices:
> 	Device: id = 3, name = /dev/sdc
> 	Device: id = 2, name = /dev/sdb
> 	Device: id = 4, name = /dev/sdd
> 	Device: id = 1, name = /dev/sda
>
> Before Recovering:
> 	[All good supers]:
> 		device name = /dev/sdc
> 		superblock bytenr = 65536
>
> 		device name = /dev/sdc
> 		superblock bytenr = 67108864
>
> 		device name = /dev/sdc
> 		superblock bytenr = 274877906944
>
> 		device name = /dev/sdb
> 		superblock bytenr = 65536
>
> 		device name = /dev/sdb
> 		superblock bytenr = 67108864
>
> 		device name = /dev/sdb
> 		superblock bytenr = 274877906944
>
> 		device name = /dev/sdd
> 		superblock bytenr = 65536
>
> 		device name = /dev/sdd
> 		superblock bytenr = 67108864
>
> 		device name = /dev/sdd
> 		superblock bytenr = 274877906944
>
> 		device name = /dev/sda
> 		superblock bytenr = 65536
>
> 		device name = /dev/sda
> 		superblock bytenr = 67108864
>
> 		device name = /dev/sda
> 		superblock bytenr = 274877906944
>
> 	[All bad supers]:
>
> All supers are valid, no need to recover
>
> I checked the filesystem:
>
> # btrfs check --readonly /dev/sda
> Opening filesystem to check...
> corrupt leaf: root=2 block=62421692628992 slot=7, bad key order, prev (7275590123520 168 11227136) current (7258421481472 168 10948608)
> corrupt leaf: root=2 block=62421692628992 slot=7, bad key order, prev (7275590123520 168 11227136) current (7258421481472 168 10948608)
> corrupt leaf: root=2 block=62421692628992 slot=7, bad key order, prev (7275590123520 168 11227136) current (7258421481472 168 10948608)
> corrupt leaf: root=2 block=62421692628992 slot=7, bad key order, prev (7275590123520 168 11227136) current (7258421481472 168 10948608)
> ERROR: failed to read block groups: Operation not permitted
> ERROR: cannot open file system
>
>