md/raid1: intialise start_next_window for READ case to avoid hang
md/raid1: intialise start_next_window for READ case to avoid hang

r1_bio->start_next_window is not initialised in the READ
case, so allow_barrier may incorrectly decrement
   conf->current_window_requests
which can cause raise_barrier() to block forever.

Fixes: 79ef3a8aa1cb1523cc231c9a90a278333c21f761
cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org (v3.13+)
Reported-by: Brassow Jonathan <b97f60d0348d610aa36b7618afc2a1f9fec67557@redhat.com>
Signed-off-by: NeilBrown <1c00aa603bb92d594c03cff60ecf8e63b2a5bcb1@suse.de>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs