You could mount the partition with the recover mount parameter, but that is not recomended unless you are instructed to do so.
I'm surprised they declared butterfs stable so fast. Good for them.
btrfs would be a bad example of "not needing defragmentation" because btrfs volumes do see file fragmentation due to the way CoW works. There is even a mount option of autodefrag to have background processes fixing the most fragmented files.Quote:
From what I know, the intention of a fsck.btrfs is not there because it should not be needed just like defragmentation.
Of course, background defragmenting beats the crap out of the mess of running a defragmenter on Windows and crippling the machine until it finishes.
Also, on the topic of mounting in recovery - I've had btrfs extent table corruption to the point where the kernel panicked if it tried to mount that volume. At that point you really need that usb repair drive. Also, in my setup, since I boot from EFIstub, I'm unable to change the kernel parameters in early boot and I can't use a recovery initrd with btrfs on it.