Created attachment 277171 [details]
The (compressed) crafted image which causes hangs
# mkdir mnt
# mount -t btrfs 15.img mnt
Not clear about the reasons...
Found by Wen Xu and Po-Ning Tseng from SSLab at Gatech.
Thanks for the report. Fixed by cf90d884b347c50 "btrfs: Introduce mount time chunk <-> dev extent mapping check", in 4.19.