On 2021/8/11 下午1:34, Konstantin Svist wrote:

On 8/10/21 22:24, Qu Wenruo wrote:

quoted

On 2021/8/11 下午1:22, Konstantin Svist wrote:

quoted

On 8/10/21 16:54, Qu Wenruo wrote:

quoted

Oh, that btrfs-map-logical is requiring unnecessary trees to continue.

Can you re-compile btrfs-progs with the attached patch?
Then the re-compiled btrfs-map-logical should work without problem.

Awesome, that worked to map the sector & mount the partition.. but I
still can't access subvol_root, where the recent data is:

Is subvol_root a subvolume?

If so, you can try to mount the subvolume using subvolume id.

But in that case, it would be not much different than using
btrfs-restore with "-r" option.

Yes it is.

# mount -oro,rescue=all,subvol=subvol_root /dev/sdb3 /mnt/
mount: /mnt: can't read superblock on /dev/sdb3.

I mean using subvolid=<number>

Using subvol= will still trigger the same path lookup code and get
aborted by the IO error.

To get the number, I guess the regular tools are not helpful.

You may want to manually exam the root tree:

# btrfs ins dump-tree -t root <device>

Then look for the keys like (<number> ROOT_ITEM <0 or number>), and try
passing the first number to "subvolid=" option.

Thanks,
Qu

dmesg has the same errors, though..

Anything else I can do?