[gentoo-user] Puzzling lvm2 behavior?

[walt]

I've never expanded an lvm partition before, and I think I did it the
long way around just now:

I divided my 1TB disk into 10 equal pv's when I bought it, and then
added four of those to a new vg (named wd0), leaving the other six
for future use.

After a few months of filling up that partition I needed more room,
of course, so I used vgextend to add a fifth pv to the existing vg.
That worked fine, but now I had to extend the ext4 fs to fill all of
the added new space.

While googling I saw some advice to use resize2fs for that, but
resize2fs said there is nothing to do on that fs and quit without
doing anything.

After some fumbling around I used lvextend -r -L nnnnn /dev/wd0/wd0,
where nnnnn is the number of unused extents listed by pvdisplay.

That (eventually) worked but each time I ran that command, only
roughly half of the empty extents were added instead of the whole
nnnnn of them.  Took me about 10 iterations before all of the
extents were finally added to the filesystem :-/

So, did I use the wrong tools or in the wrong order, or what?
It should have been easier than that, I think.