From: Tian Lan <tian.lan@xxxxxxxxxxxx>
The nr_active counter continues to increase over time which causes the
blk_mq_get_tag to hang until the thread is rescheduled to a different
core despite there are still tags available.
kernel-stack
INFO: task inboundIOReacto:3014879 blocked for more than 2 seconds
Not tainted 6.1.15-amd64 #1 Debian 6.1.15~debian11
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:inboundIORe state:D stack:0 pid:3014879 ppid:4557 flags:0x00000000
Call Trace:
<TASK>
__schedule+0x351/0xa20
scheduler+0x5d/0xe0
io_schedule+0x42/0x70
blk_mq_get_tag+0x11a/0x2a0
? dequeue_task_stop+0x70/0x70
__blk_mq_alloc_requests+0x191/0x2e0
kprobe output showing RQF_MQ_INFLIGHT bit is not cleared before
__blk_mq_free_request being called.
320 320 kworker/29:1H __blk_mq_free_request rq_flags 0x220c0
b'__blk_mq_free_request+0x1 [kernel]'
b'bt_iter+0x50 [kernel]'
b'blk_mq_queue_tag_busy_iter+0x318 [kernel]'
b'blk_mq_timeout_work+0x7c [kernel]'
b'process_one_work+0x1c4 [kernel]'
b'worker_thread+0x4d [kernel]'
b'kthread+0xe6 [kernel]'
b'ret_from_fork+0x1f [kernel]'
This issue arises when both bt_iter() and blk_mq_end_request_batch()
are iterating on the same request. The leak happens when
blk_mq_find_and_get_req() is executed(from bt_iter) before
req_ref_put_and_test() gets called by blk_mq_end_request_batch().
And because non-flush request freed by blk_mq_put_rq_ref() bypasses the
active request tracking, the counter would slowly leak overtime.
Fixes: f794f3351f26 ("block: add support for blk_mq_end_request_batch()")
Fixes: 2e315dc07df0 ("blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter")
Signed-off-by: Tian Lan <tian.lan@xxxxxxxxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
block/blk-mq.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index f6dad0886a2f..850bfb844ed2 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -683,6 +683,10 @@ static void __blk_mq_free_request(struct request *rq)
blk_crypto_free_request(rq);
blk_pm_mark_last_busy(rq);
rq->mq_hctx = NULL;
+
+ if (rq->rq_flags & RQF_MQ_INFLIGHT)
+ __blk_mq_dec_active_requests(hctx);
+
if (rq->tag != BLK_MQ_NO_TAG)
blk_mq_put_tag(hctx->tags, ctx, rq->tag);
if (sched_tag != BLK_MQ_NO_TAG)
@@ -694,15 +698,11 @@ static void __blk_mq_free_request(struct request *rq)
void blk_mq_free_request(struct request *rq)
{
struct request_queue *q = rq->q;
- struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
if ((rq->rq_flags & RQF_ELVPRIV) &&
q->elevator->type->ops.finish_request)
q->elevator->type->ops.finish_request(rq);
- if (rq->rq_flags & RQF_MQ_INFLIGHT)
- __blk_mq_dec_active_requests(hctx);
-
if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
laptop_io_completion(q->disk->bdi);
--
2.25.1
