Xbian on ext4 file-system??

[MacUsers]

I'm very confused now. This is exactly what I have as my cmdline.txt:

Code:

xbian@xbian ~ $ cat /boot/cmdline.txt
#sdhci-bcm2708.sync_after_dma=0 dwc_otg.lpm_enable=0 console=tty1 root=LABEL=xbian-beta2 rootflags=subvol=root/@,autodefrag,compress=lzo rootfstype=btrfs rootwait smsc95xx.turbo_mode=N elevator=cfq logo.nologo quiet noswap loglevel=0 mod_scsi.scan=sync partswap startevent=mountall splash nohdparm --startup-event mountall loglevel=0

sdhci-bcm2708.sync_after_dma=0 dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootflags=subvol=root/@,autodefrag,compress=lzo rootfstype=btrfs rootwait smsc95xx.turbo_mode=N elevator=cfq logo.nologo quiet noswap loglevel=0 mod_scsi.scan=sync partswap startevent=mountall splash nohdparm --startup-event mountall loglevel=0

and after the boot, this is what I see mounted:

Code:

xbian@xbian ~ $ mount
/dev/sda1 on / type btrfs (rw,relatime,compress=lzo,ssd,space_cache,autodefrag)
devtmpfs on /dev type devtmpfs (rw,relatime,size=191796k,nr_inodes=47949,mode=755)
none on /dev/pts type devpts (rw,nosuid,noexec,relatime,mode=600)
none on /proc type proc (rw,nosuid,nodev,noexec,relatime)
none on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
none on /run type tmpfs (rw,nosuid,nodev,noexec,noatime,size=38376k)
/dev/mmcblk0p1 on /boot type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=ascii,shortname=mixed,​errors=remount-ro)
/dev/sda1 on /home type btrfs (rw,noatime,compress=lzo,ssd,space_cache,autodefrag)
/dev/sda1 on /lib/modules type btrfs (rw,noatime,compress=lzo,ssd,space_cache,autodefrag)
/dev/sda1 on /xbmc-backup type btrfs (rw,noatime,compress=lzo,ssd,space_cache,autodefrag)

Can anyone please explain how /dev/sda1 is being used instead of /dev/mmcblk0p2 as specified in the cmdline.txt?