I'm hoping to gain some ideas around recovering a disk prior to giving up. I've been using btrfs for ~4 years and have never had something like this happen to me. In the past 2 days, I've had system freezes and found that dmesg reported remounting ro. I booted into a USB stick to investigate. I don't easily have a way to get my log files from recovery USB to my wife's computer, so I'm summarizing the issues to see what the resolution might be for each. With btrfs check, I had many errors like this: ``` ref mismatch on [xxxxx yyyyy] extent item 0, found 1 tree backref xxxx parent 268 root 268 not found in extent tree backpointer mismatch on [xxxx yyyy] ``` At the end: ``` cache and super generation don't match, space cache will invalidated ``` After trying various options (--repair, --init-extent-tree) and deleting some offending subvols I no longer needed/cared about, I now cannot boot. I can mount each subvol, but not boot due to inability to find btree root. Upon btrfs check /dev/mapper/root, now I get: ``` root item for root 260, current bytenr 110231994368, current gen, 274095, current level 2, new bytenr 25362432, new gen 222067, new level 1 root has a root item with a more recent gen (274095) compared to the found root node (222067) ERROR: failed to repair root items: Invalid argument ``` I can mount the subvol used for my root partition, but get this on umount: ``` BTRFS error (device dm-0): unable to find ref bytenr 5767168 parent 0 root 2 owner 0 offset 0 BTRFS: error (device dm-0): in __btrfs_free_extent:6828: errno=-2 No such entry BTRFS: error (device dm-0): in btrfs_run_delayed_refs:2970: errno=-2 No such entry BTRFS: error (device dm-0): in cleanup_transaction:1849: errno=-2 No such entry ``` I'm happy to provide further information. As you can imagine, having a primary system go down is... cumbersome. Working a lot off my phone to try and troubleshoot and am having a pretty hard time finding error reports matching these, along with what one would do to resolve. I'll get an ubuntu boot disk made so I can use a browser (arch's is just cli) and post more details upon request. I'm backed up, but hope that the fact I can mount everything means this is sort of an "accounting" error vs. anything serious. I just don't know how to resolve it. arch linux, kernel 5.3 btrfs-progs 5.4 Many thanks, John
