blktrace: Don't tear down devices we didn't set up

[Jeff Mahoney <jeffm@suse.com>]

If we have two copies of blktrace trying to operate on the same device, one
will fail to set up, as expected. It then tears down the devices it was
configured to use, but does so even if they weren't setup by that instance.

This can result in tearing down running traces, which will end up leaving
the debugfs files around without a way to clean them up. Further instances
of blktrace on that device will fail.

This patch ensures we only clean up the devices we've set up.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
---
 blktrace.c |   21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

--- a/blktrace.c
+++ b/blktrace.c
@@ -1048,7 +1048,7 @@ static void close_client_connections(voi
 	}
 }
 
-static void setup_buts(void)
+static int setup_buts(void)
 {
 	struct list_head *p;
 
@@ -1068,10 +1068,13 @@ static void setup_buts(void)
 				free(dpp->stats);
 			dpp->stats = calloc(dpp->ncpus, sizeof(*dpp->stats));
 			memset(dpp->stats, 0, dpp->ncpus * sizeof(*dpp->stats));
-		} else
-			fprintf(stderr, "BLKTRACESETUP(2) %s failed: %d/%s\n",
+		} else {
+			fprintf(stderr, "BLKTRACESETUP for %s failed: %d/%s\n",
 				dpp->path, errno, strerror(errno));
+			return -1;
+		}
 	}
+	return 0;
 }
 
 static void start_buts(void)
@@ -1262,7 +1265,10 @@ static void rel_devpaths(void)
 		struct devpath *dpp = list_entry(p, struct devpath, head);
 
 		list_del(&dpp->head);
-		__stop_trace(dpp->fd);
+
+		/* Only stop it if we set it up */
+		if (dpp->buts_name)
+			__stop_trace(dpp->fd);
 		close(dpp->fd);
 
 		if (dpp->heads)
@@ -2597,11 +2603,16 @@ out:
 
 static int run_tracers(void)
 {
+	int ret;
 	atexit(exit_tracing);
 	if (net_mode = Net_client)
 		printf("blktrace: connecting to %s\n", hostname);
 
-	setup_buts();
+	ret = setup_buts();
+	if (ret) {
+		fprintf(stderr, "Failed to enable some targets. Exiting.\n");
+		return ret;
+	}
 
 	if (use_tracer_devpaths()) {
 		if (setup_tracer_devpaths())

-- 
Jeff Mahoney
SUSE Labs