Improve missing-kernel-driver error message.

diff --git a/lib/ioctl/libdevmapper.c b/lib/ioctl/libdevmapper.c
index b33e53306121a7ae73008ffce55734a49310da0b..028e034c6f71d9b6a8c9f16dbc5c57249d366e4b 100644 (file)
--- a/lib/ioctl/libdevmapper.c
+++ b/lib/ioctl/libdevmapper.c
@@ -351,7 +351,8 @@ int dm_task_run(struct dm_task *dmt)
        snprintf(control, sizeof(control), "%s/control", dm_dir());
 
        if ((fd = open(control, O_RDWR)) < 0) {
-               log_error("Couldn't open device-mapper control device");
+               log_error("%s: open failed: %s", control, strerror(errno));
+               log_error("Is device-mapper driver missing from kernel?");
                goto bad;
        }