md/raid10: wait barrier before returning discard request with REQ_NOWAIT

md/raid10: wait barrier before returning discard request with REQ_NOWAIT

[ Upstream commit 3db4404435397a345431b45f57876a3df133f3b4 ]

raid10_handle_discard should wait barrier before returning a discard bio
which has REQ_NOWAIT. And there is no need to print warning calltrace
if a discard bio has REQ_NOWAIT flag. Quality engineer usually checks
dmesg and reports error if dmesg has warning/error calltrace.

Fixes: c9aa889b035f ("md: raid10 add nowait support")
Signed-off-by: Xiao Ni <xni@redhat.com>
Acked-by: Coly Li <colyli@kernel.org>
Link: https://lore.kernel.org/linux-raid/20250306094938.48952-1-xni@redhat.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
[Harshit: Clean backport to 6.12.y]
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>