[PATCH] tools/xenstored: Propagate correctly the error message from lu_start()

[Julien Grall <julien@xxxxxxx>]

From: Julien Grall <jgrall@xxxxxxxxxx>

lu_start() will only set errno when it returns NULL. For all the
other cases, the value is unknown.

This means that when lu_start() returns an error message, it may not
be propagated to the client.

The check that errno is a non-zero value is now dropped and instead
the value is returned when no error message is provided. This
relies on errno to always be set when ret == NULL.

Fixes: af216a99fb ("tools/xenstore: add the basic framework for doing the live 
update")
Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 tools/xenstore/xenstored_control.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/tools/xenstore/xenstored_control.c 
b/tools/xenstore/xenstored_control.c
index ff9863c17fa4..6b68b79faac7 100644
--- a/tools/xenstore/xenstored_control.c
+++ b/tools/xenstore/xenstored_control.c
@@ -795,10 +795,8 @@ static int do_control_lu(void *ctx, struct connection 
*conn,
                                return EINVAL;
                }
                ret = lu_start(ctx, conn, force, to);
-               if (errno)
-                       return errno;
                if (!ret)
-                       return 0;
+                       return errno;
        } else {
                errno = 0;
                ret = lu_arch(ctx, conn, vec, num);
-- 
2.17.1