This has come up a few times over the past month (e.g. [Solved - kinda] Can't log in : BTRFS: error in btrfs_run_delayed_refs:2124: errno:-5 IO failure, BTRFS error : system boot in emergency mode).
A quick web search (Garuda searxng) leads to this thread on the Arch BBS:
https://bbs.archlinux.org/viewtopic.php?pid=1772672#p1772672
and that might provide a starting point.
In any event, make sure you have a backup of any important data.