Just unmount the dos partition, fix and remount while the pi is running?

#aptitude install dosfstools
#mount
#umount /dev/mmcblk0p1
#dosfsck -t -a -w /dev/mmcblk0p1
#mount /dev/mmcblk0p1

root@weather:~# dosfsck -t -a -w /dev/mmcblk0p1
fsck.fat 3.0.27 (2014-11-12)
0x41: Dirty bit is set. Fs was not properly unmounted and some data may be corrupt.
Automatically removing dirty bit.
Performing changes.
/dev/mmcblk0p1: 58 files, 79271/100792 clusters
root@weather:~# dosfsck -t -a -w /dev/mmcblk0p1
fsck.fat 3.0.27 (2014-11-12)
/dev/mmcblk0p1: 58 files, 79271/100792 clusters
root@weather:~# mount /dev/mmcblk0p1

And so I know it is fixed:
root@pi-sprinkler:~# echo “Fixed the DOS FS today” > /dev/kmsg