commit 9e0d8768 upstream.

Refactor to separate out the functions of starting and stopping threads
so that they can be used in other helpers.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Tested-and-reviewed-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Cc: Jan Hudoba <kernel@jahu.sk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>