From 3f8cadf8435fa3c9b0fe8aa1f7e2a50832310560 Mon Sep 17 00:00:00 2001
From: weiping zhang <zhangweiping@didichuxing.com>
Date: Mon, 15 Jan 2018 23:53:42 +0800
Subject: [PATCH 04/15] blktrace: don't stop tracer if not setup trace
 successfully

if we run blktrace on same device twice, the second time will failed
to ioctl(BLKTRACESETUP), then it will call __stop_tracer, which lead
the first blktrace failed to access debugfs entries. So this patch add
a check to handle this case, to avoid stop tracer uncondionally.

Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 blktrace.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/blktrace.c b/blktrace.c
index e048f68..d0d271f 100644
--- a/blktrace.c
+++ b/blktrace.c
@@ -112,6 +112,7 @@ struct devpath {
 	struct cl_host *ch;
 	u32 cl_id;
 	time_t cl_connect_time;
+	int setup_done;	/* ioctl BLKTRACESETUP done */
 	struct io_info *ios;
 };
 
@@ -1083,6 +1084,7 @@ static int setup_buts(void)
 		if (ioctl(dpp->fd, BLKTRACESETUP, &buts) >= 0) {
 			dpp->ncpus = max_cpus;
 			dpp->buts_name = strdup(buts.name);
+			dpp->setup_done = 1;
 			if (dpp->stats)
 				free(dpp->stats);
 			dpp->stats = calloc(dpp->ncpus, sizeof(*dpp->stats));
@@ -1285,7 +1287,8 @@ static void rel_devpaths(void)
 		struct devpath *dpp = list_entry(p, struct devpath, head);
 
 		list_del(&dpp->head);
-		__stop_trace(dpp->fd);
+		if (dpp->setup_done)
+			__stop_trace(dpp->fd);
 		close(dpp->fd);
 
 		if (dpp->heads)
-- 
1.8.3.1