sunrpc: add a rcu_head to svc_rqst and use kfree_rcu to free it

...also make the manipulation of sp_all_threads list use RCU-friendly
functions.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Tested-by: Chris Worley <chris.worley@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 5f0ab39..7f80a99 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -223,6 +223,7 @@
 struct svc_rqst {
 	struct list_head	rq_list;	/* idle list */
 	struct list_head	rq_all;		/* all threads list */
+	struct rcu_head		rq_rcu_head;	/* for RCU deferred kfree */
 	struct svc_xprt *	rq_xprt;	/* transport ptr */
 
 	struct sockaddr_storage	rq_addr;	/* peer address */
@@ -262,6 +263,7 @@
 #define	RQ_SPLICE_OK	(4)			/* turned off in gss privacy
 						 * to prevent encrypting page
 						 * cache pages */
+#define	RQ_VICTIM	(5)			/* about to be shut down */
 	unsigned long		rq_flags;	/* flags field */
 
 	void *			rq_argp;	/* decoded arguments */