FFS write coalescing

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I could find out myself by digging through the source, but probabely someone
here knows the answer off his head:
When FFS does write coalescing, will it try to align the resulting 64k chunk?
I.e., if I have 32k blocks and I write blocks 1, 2, 3, 4; will it write (1,2)
and (3,4) or 1, (2,3) and 4?
Of course, the background for my question is RAID stripe alignment.