Re: Write I/O queue hangup at random on recent Linus' kernels

Jens Axboe
2021-11-26T16:53:26Z

On 11/25/21 2:07 PM, Jens Axboe wrote:
> On 11/25/21 2:05 PM, Kenneth R. Crudup wrote:
>>
>> On Tue, 23 Nov 2021, Jens Axboe wrote:
>>
>>> It looks like some missed accounting. You can just disable wbt for now, would
>>> be a useful data point to see if that fixes it. Just do:
>>
>>> echo 0 > /sys/block/nvme0n1/queue/wbt_lat_usec
>>
>>> and that will disable writeback throttling on that device.
>>
>> It's been about 48 hours and haven't seen the issue since doing this.
>
> Great, thanks for verifying. From your report 5.16-rc2 has the issue, is
> 5.15 fine?

Can you apply this on top of 5.16-rc2 or current -git and see if it fixes
it for you?

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8799fa73ef34..8874a63ae952 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -860,13 +860,14 @@ void blk_mq_end_request_batch(struct io_comp_batch *iob)
if (iob->need_ts)
__blk_mq_end_request_acct(rq, now);

+ rq_qos_done(rq->q, rq);
+
WRITE_ONCE(rq->state, MQ_RQ_IDLE);
if (!refcount_dec_and_test(&rq->ref))
continue;

blk_crypto_free_request(rq);
blk_pm_mark_last_busy(rq);
- rq_qos_done(rq->q, rq);

if (nr_tags == TAG_COMP_BATCH || cur_hctx != rq->mq_hctx) {
if (cur_hctx)

--
Jens Axboe