/etc/fstab rootfs options vs grub2 rootflags cmdline

["Niccolò Belli" <darkbasic@linuxsystems.it>]

Hi,
I have the following options for my rootfs in /etc/fstab:
rw,relatime,compress=lzo,ssd,discard,space_cache,autodefrag,subvolid=257,subvol=/@

grub2 already placed rootflags=subvol=@ in its cmdline, but not the other 
options. I suppose that some of them will automatically be set during 
remount, but I'm not sure if all of them will.

Do you know which ones should I manually add to GRUB_CMDLINE_LINUX in 
/etc/default/grub?

Is there any way to check to if they are already enabled?
mount shows /dev/mapper/cryptroot on / type btrfs 
(rw,relatime,compress=lzo,ssd,discard,space_cache,autodefrag,subvolid=257,subvol=/@) 
but I'm not sure if I can trust it: I read that space_cache should trigger 
"enabling free space tree" in dmesg but I can't see it and I don't know 
about the others.

Thanks,
Niccolò