By the way, if you want to try repairs, I know that you're using an image on loop. But it could still save you time to set up an overlay to avoid modifying the image until you've found a combination that works - if possible. https://raid.wiki.kernel.org/index.php/Recovering_a_failed_software_RAID#Making_the_harddisks_read-only_using_an_overlay_file This strikes me as extent tree corruption so I'd start with --init-extent-tree, and follow that up without options (implies --readonly). There is no bigger hammer, so it's worth a shot but only because you're working on a copy of the fs. There's a chance it makes things worse. -- Chris Murphy
