Comment # 9 on bug 915575 from Thomas Blume

Yeah, there is a problem due to device timeout:

-->--
Job
dev-disk-by\x2duuid-d256e954\x2df026\x2d417a\x2da6cf\x2d472093b98a5e.device/start
timed out.
Job
dev-disk-by\x2duuid-d256e954\x2df026\x2d417a\x2da6cf\x2d472093b98a5e.device/start
finished, result=timeout
--<--

Which is pretty strange, because btrfs can apparently see the device: 

-->--
Got [    4.700082] BTRFS: device fsid d256e954-f026-417a-a6cf-472093b98a5e
message type=sigdevid 1 transid 29954 /dev/sda3
--<--

The system seems to go into the emergency mode.
Can you please also add the following boot parameters:

debug rd.debug udev.log-priority=debug rd.udev.log-priority=debug

and attach /run/initramfs/rdsosreport.txt when it is there?