blktrace: don't increase blk_probes_ref if failed to setup blk trace
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>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <49C2F5FF.80002@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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 @@
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 @@
goto err;
}
+ if (atomic_add_return(1, &blk_probes_ref) == 1)
+ blk_register_tracepoints();
+
return 0;
err:
if (bt) {
