Add one more error reason statement to blktapctrl

Hi,
I had an issue with blktapctrl on xen-ppc.
The reason is easy - currently we have no blktap in our linux tree, but because blktapctrl did not print out a useful error statement in my case I struggled a while to find the reason. I also saw no useful module error messages because it is not damaged, its just not there in my case.
This patch adds an error message if xc_find_device_number fails, all other goto's to open_failed have already their error output, this just adds one more.

Grüsse / regards, Christian Ehrhardt

IBM Linux Technology Center, Open Virtualization
+49 7031/16-3385
[email protected]
[email protected]

IBM Deutschland Entwicklung GmbH
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# HG changeset patch
# User Christian Ehrhardt <[email protected]>
# Date 1179814369 -7200
# Node ID 6d25bbfcb3e2ce7660b5253431b0b9638d1df1bc
# Parent be31124bbec216693cb5758ee2e6d87b3fd292b2
[XEN][TOOLS][PATCH] 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/...

diff -r be31124bbec2 -r 6d25bbfcb3e2 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);

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