md: separate request handling

md: separate request handling

commit 393debc23c7820211d1c8253dd6a8408a7628fe7 upstream.

With commit cc27b0c78c79, pers->make_request could bail out without handling
the bio. If that happens, we should retry.  The commit fixes md_make_request
but not other call sites. Separate the request handling part, so other call
sites can use it.

Reported-by: Nate Dailey <nate.dailey@stratus.com>
Fix: cc27b0c78c79(md: fix deadlock between mddev_suspend() and md_write_start())
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>