block migration: fix return value

Modify block_save_iterate() to return positive/zero/negative
(success/not done/failure) return status. The computation of
the blocks transferred (an int64_t) exceeds the size of an
int return value.

Signed-off-by: Gary R Hook <gary.hook@nimboxx.com>
Reviewed-by: ChenLiang <chenliang88@huawei.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1416958202-15913-1-git-send-email-gary.hook@nimboxx.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit ebd9fbd7e102c533143c2c8372312b75c2b2678a)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

block-migration.c

@@ -652,6 +652,7 @@ static int block_save_iterate(QEMUFile *f, void *opaque)
 {
     int ret;
     int64_t last_ftell = qemu_ftell(f);
+    int64_t delta_ftell;
 
     DPRINTF("Enter save live iterate submitted %d transferred %d\n",
             block_mig_state.submitted, block_mig_state.transferred);
@@ -701,7 +702,14 @@ static int block_save_iterate(QEMUFile *f, void *opaque)
     }
 
     qemu_put_be64(f, BLK_MIG_FLAG_EOS);
-    return qemu_ftell(f) - last_ftell;
+    delta_ftell = qemu_ftell(f) - last_ftell;
+    if (delta_ftell > 0) {
+        return 1;
+    } else if (delta_ftell < 0) {
+        return -1;
+    } else {
+        return 0;
+    }
 }
 
 /* Called with iothread lock taken.  */