Re: [PATCH v1] block/mq-deadline: hold elevator_lock in debugfs next_rq show
From: Bart Van Assche
Date: Wed Jul 22 2026 - 13:58:08 EST
On 7/20/26 11:30 PM, Xixin Liu wrote:
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index 824bfc17b2c6..e7c4a91b2d08 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -842,14 +842,22 @@ static int deadline_##name##_next_rq_show(void *data, \
struct seq_file *m) \
{ \
struct request_queue *q = data; \
- struct deadline_data *dd = q->elevator->elevator_data; \
- struct dd_per_prio *per_prio = &dd->per_prio[prio]; \
+ struct elevator_queue *e; \
+ struct deadline_data *dd; \
+ struct dd_per_prio *per_prio; \
struct request *rq; \
+ int ret; \
\
+ ret = mutex_lock_interruptible(&q->elevator_lock); \
+ if (ret) \
+ return ret; \
+ e = q->elevator; \
+ if (!e) \
+ goto unlock; \
+ dd = e->elevator_data; \
+ per_prio = &dd->per_prio[prio]; \
rq = deadline_from_pos(per_prio, data_dir, \
per_prio->latest_pos[data_dir]); \
if (rq) \
__blk_mq_debugfs_rq_show(m, rq); \
+unlock: \
+ mutex_unlock(&q->elevator_lock); \
return 0; \
}
The above patch uses the wrong lock and brings way too much code under
the lock. Please help with testing this patch:
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index 6e8f87e07eb9..c52601c1fa13 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -850,6 +850,7 @@ static int deadline_##name##_next_rq_show(void *data, \
struct dd_per_prio *per_prio = &dd->per_prio[prio]; \
struct request *rq; \
\
+ guard(spinlock)(&dd->lock); \
rq = deadline_from_pos(per_prio, data_dir, \
per_prio->latest_pos[data_dir]); \
if (rq) \