blktap: Add one more error reason statement to blktapctrl

blktapctrl already prints out exits reasons for all goto's to
open_failed except of not finding a device number for blktap0
This patch adds just that message so the user will get more info than
just "Unable to start blktapctrl"
Common source of this issue is that blktap is missing/failed to
load/...

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>

diff --git a/tools/blktap/drivers/blktapctrl.c b/tools/blktap/drivers/blktapctrl.c
index 42b74b3c7adeda42a94cd40893fe14c870fb8240..a0b2f349d0753197d33ecbe61a7ec22056401d66 100644 (file)
--- a/tools/blktap/drivers/blktapctrl.c
+++ b/tools/blktap/drivers/blktapctrl.c
@@ -690,8 +690,10 @@ int main(int argc, char *argv[])
 
        /* Attach to blktap0 */
        asprintf(&devname,"%s/%s0", BLKTAP_DEV_DIR, BLKTAP_DEV_NAME);
-       if ((ret = xc_find_device_number("blktap0")) < 0)
+       if ((ret = xc_find_device_number("blktap0")) < 0) {
+               DPRINTF("couldn't find device number for 'blktap0'\n");
                goto open_failed;
+       }
        blktap_major = major(ret);
        make_blktap_dev(devname,blktap_major,0);
        ctlfd = open(devname, O_RDWR);