rcu: Update docs to include kfree_rcu()

Mention kfree_rcu() in the call_rcu() section.  Additionally fix the
example code for list replacement that used the wrong structure element.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Documentation/RCU/listRCU.txt

@@ -205,7 +205,7 @@ RCU ("read-copy update") its name.  The RCU code is as follows:
 				audit_copy_rule(&ne->rule, &e->rule);
 				ne->rule.action = newaction;
 				ne->rule.file_count = newfield_count;
-				list_replace_rcu(e, ne);
+				list_replace_rcu(&e->list, &ne->list);
 				call_rcu(&e->rcu, audit_free_rule);
 				return 0;
 			}

Documentation/RCU/whatisRCU.txt

@@ -499,6 +499,8 @@ The foo_reclaim() function might appear as follows:
 	{
 		struct foo *fp = container_of(rp, struct foo, rcu);
 
+		foo_cleanup(fp->a);
+
 		kfree(fp);
 	}
 
@@ -521,6 +523,12 @@ o	Use call_rcu() -after- removing a data element from an
 	read-side critical sections that might be referencing that
 	data item.
 
+If the callback for call_rcu() is not doing anything more than calling
+kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
+to avoid having to write your own callback:
+
+	kfree_rcu(old_fp, rcu);
+
 Again, see checklist.txt for additional rules governing the use of RCU.
 
 
@@ -773,8 +781,8 @@ a single atomic update, converting to RCU will require special care.
 
 Also, the presence of synchronize_rcu() means that the RCU version of
 delete() can now block.  If this is a problem, there is a callback-based
-mechanism that never blocks, namely call_rcu(), that can be used in
-place of synchronize_rcu().
+mechanism that never blocks, namely call_rcu() or kfree_rcu(), that can
+be used in place of synchronize_rcu().
 
 
 7.  FULL LIST OF RCU APIs
@@ -813,6 +821,7 @@ RCU:	Critical sections	Grace period		Barrier
 	rcu_read_unlock		synchronize_rcu
 	rcu_dereference		synchronize_rcu_expedited
 				call_rcu
+				kfree_rcu
 
 
 bh:	Critical sections	Grace period		Barrier