[RFC PATCH] blktrace: fail earlier if blk_trace in use

[weiping zhang <zhangweiping@xxxxxxxxxxxxxxx>]

add a check before allocate resource for blk_trace, if it's in use.

Signed-off-by: weiping zhang <zhangweiping@xxxxxxxxxxxxxxx>
---
 kernel/trace/blktrace.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 987d9a9a..16c0000 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -491,6 +491,9 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 	struct dentry *dir = NULL;
 	int ret;
 
+	if (unlikely(q->blk_trace))
+		return -EBUSY;
+
 	if (!buts->buf_size || !buts->buf_nr)
 		return -EINVAL;
 
-- 
2.9.4