staging: lustre: kg_sem semaphore handling is incorrectly

During the removal of the cfs wrappers the kg_sem semaphore
was handled incorrectly. We need to take a write lock when
writing data to the kkuc_groups. The libcfs_kkuc_group_foreach
needs to only take a read lock. This makes use match the
OpenSFS development branch.
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/libcfs/kernel_user_comm.c

@@ -186,7 +186,7 @@ int libcfs_kkuc_group_put(int group, void *payload)
 	int		 rc = 0;
 	int one_success = 0;
 
-	down_read(&kg_sem);
+	down_write(&kg_sem);
 	list_for_each_entry(reg, &kkuc_groups[group], kr_chain) {
 		if (reg->kr_fp != NULL) {
 			rc = libcfs_kkuc_msg_put(reg->kr_fp, payload);
@@ -198,7 +198,7 @@ int libcfs_kkuc_group_put(int group, void *payload)
 			}
 		}
 	}
-	up_read(&kg_sem);
+	up_write(&kg_sem);
 
 	/* don't return an error if the message has been delivered
 	 * at least to one agent */
@@ -230,12 +230,12 @@ int libcfs_kkuc_group_foreach(int group, libcfs_kkuc_cb_t cb_func,
 	if (kkuc_groups[group].next == NULL)
 		return 0;
 
-	down_write(&kg_sem);
+	down_read(&kg_sem);
 	list_for_each_entry(reg, &kkuc_groups[group], kr_chain) {
 		if (reg->kr_fp != NULL)
 			rc = cb_func(reg->kr_data, cb_arg);
 	}
-	up_write(&kg_sem);
+	up_read(&kg_sem);
 
 	return rc;
 }