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

[Edward Adam Davis]

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

Reported-and-tested-by: syzbot+2373f6be3e6de4f92...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eada...@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