[PATCH] trace/blktrace: fix task hung in blk_trace_remove

[Edward Adam Davis <eadavis@qq.com>]

Delete critical sections that are time-consuming and protected by other mutexes
to avoid this issue.

Reported-and-tested-by: syzbot+2373f6be3e6de4f92562@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
 kernel/trace/blktrace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index d5d94510afd3..4543be718362 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -313,6 +313,7 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 
 static void blk_trace_free(struct request_queue *q, struct blk_trace *bt)
 {
+	mutex_unlock(&q->debugfs_mutex);
 	relay_close(bt->rchan);
 
 	/*
@@ -325,6 +326,7 @@ static void blk_trace_free(struct request_queue *q, struct blk_trace *bt)
 	} else {
 		debugfs_remove(bt->dir);
 	}
+	mutex_lock(&q->debugfs_mutex);
 	free_percpu(bt->sequence);
 	free_percpu(bt->msg_data);
 	kfree(bt);
-- 
2.43.0