I ran btrfs scrub and got this:
scrub status for 57cf76da-ea78-43d3-94d3-0976308bb4cc
scrub started at Wed Mar 15 10:30:16 2017 and finished after 00:16:39
total bytes scrubbed: 390.45GiB with 28 errors
error details: csum=28
corrected errors: 0, uncorrectable errors: 28, unverified errors: 0
OK, I have good backups, and I would like to know which files these 28 errors are in so I can restore them from backup. That would save me a lot of time over wiping and restoring the whole disk.