[PATCH 4/7] blktrace: don't increase blk_probes_ref if failed to setup blk trace

[Li Zefan <lizf@cn.fujitsu.com>]

do_blk_trace_setup() may return EBUSY, but the current code doesn't
decrease blk_probes_ref in this case.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 kernel/trace/blktrace.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 223b92e..11e7c8d 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -468,9 +468,6 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 	bt->pid = buts->pid;
 	bt->trace_state = Blktrace_setup;
 
-	if (atomic_add_return(1, &blk_probes_ref) == 1)
-		blk_register_tracepoints();
-
 	ret = -EBUSY;
 	old_bt = xchg(&q->blk_trace, bt);
 	if (old_bt) {
@@ -478,6 +475,9 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 		goto err;
 	}
 
+	if (atomic_add_return(1, &blk_probes_ref) == 1)
+		blk_register_tracepoints();
+
 	return 0;
 err:
 	if (bt) {
-- 
1.5.4.rc3