mainline inclusion
from md-next
commit 7fdc91928ac109d3d1468ad7f951deb29a375e3d
category: performance
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5PRMO
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/song/md.git/commit/?h=md-next&id=7fdc91928ac109d3d1468ad7f951deb29a375e3d

--------------------------------

Currently, wake_up() is called unconditionally in fast path such as
raid10_make_request(), which will cause lock contention under high
concurrency:

raid10_make_request
 wake_up
  __wake_up_common_lock
   spin_lock_irqsave

Improve performance by only call wake_up() if waitqueue is not empty.
Signed-off-by: NYu Kuai <yukuai3@huawei.com>
Reviewed-by: NLogan Gunthorpe <logang@deltatee.com>
Acked-by: NGuoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: NSong Liu <song@kernel.org>
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>