Days-long wait for completion of "btrfs check --repair"

I am running openSuSe Leap 42.2 on a Lenovo X1-Yoga with a nominally 512GB ATA Sandisk hard drive, the root partition being /dev/sda6. The machine failed to boot after an Online Update. Using the “Rescue System” from a bootable USB key I ran

btrfs check -p --repair /dev/sda6

. It is now about 40 hours since I issued that command, and the machine is repeatedly outputting the same message:

Found file extent holes:
start: 0, len: 909312
root 908 inode 819289 errors 100, file extent discount

Should I assume something useful is being done, and continue to wait? Thanks, John