After reinstalling Ubuntu on a secondary partition macOS started to boot slower than usual. I tried to check the main APFS volume and encountered some errors. FSCK_APFS was unable to recover this volume (all modes, recovery, single-user). There is no full APFS documentation available in public. No structure explanation. So is it possible to repair APFS manually? Is there any datasheet? What is "fsroot tree" in APFS? Why can it be invalid?
fsck_apfs -y -d /dev/rdisk2s1 Checking volume. Checking the container superblock. Checking the EFI jumpstart record. Checking the space manager. Checking the object map. Checking the APFS volume superblock. Checking the object map. Checking the fsroot tree. error: inode_val: object (oid 0xf8aa9): invalid parent_id (0x0) obj-id: 1010537 type: Inode private-id: 1010538 parent-id: 0 cr/mtime: 0/0 def-prot-class: -1 uid/gid/mode 0/0/0x81a4 bsd_flags: 0x0 internal_flags: 0x0000 name: NO-NAME fsroot tree is invalid. The volume /dev/rdisk2s1 could not be verified completely.