[PATCH] VM: fix zone list restart in page allocatate

We must reassign z before looping through the zones kicking kswapd,
since it will be NULL if we hit an OOM condition and jump back to the
beginning again. 'z' is initially assigned before the restart: label. So
move the restart label up a little.

Signed-off-by: Jens Axboe <axboe@suse.de>