On Fri, 2017-11-03 at 23:18 +0800, Ming Lei wrote:
> Subject: [PATCH] SCSI_MQ: fix IO hang in case of queue busy
>
> We have to insert the rq back before checking .device_busy,
> otherwise When IO completes just after the check and before
> this req is added to hctx->dispatch, this queue may never get
> chance to be run, then this IO may hang forever.
>
> This patch introduces BLK_STS_RESOURCE_OK for handling this
> issue.
>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
> block/blk-mq.c | 17 +++++++++++++++++
> drivers/scsi/scsi_lib.c | 8 ++++++++
> include/linux/blk-mq.h | 1 +
> include/linux/blk_types.h | 1 +
> 4 files changed, 27 insertions(+)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index e4d2490f4e7e..e1e03576edca 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -660,6 +660,16 @@ static void __blk_mq_requeue_request(struct request *rq)
> }
> }
>
> +void blk_mq_reinsert_request_hctx(struct blk_mq_hw_ctx *hctx, struct request *rq)
> +{
> + __blk_mq_requeue_request(rq);
> +
> + spin_lock(&hctx->lock);
> + list_add_tail(&rq->queuelist, &hctx->dispatch);
> + spin_unlock(&hctx->lock);
> +}
> +EXPORT_SYMBOL(blk_mq_reinsert_request_hctx);
> +
> void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
> {
> __blk_mq_requeue_request(rq);
> @@ -1165,6 +1175,12 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
> list_add(&rq->queuelist, list);
> __blk_mq_requeue_request(rq);
> break;
> + } else if (ret == BLK_STS_RESOURCE_OK) {
> + /*
> + * BLK_STS_RESOURCE_OK means driver handled this
> + * STS_RESOURCE already, we just need to stop dispatch.
> + */
> + break;
> }
>
> fail_rq:
> @@ -1656,6 +1672,7 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
> ret = q->mq_ops->queue_rq(hctx, &bd);
> switch (ret) {
> case BLK_STS_OK:
> + case BLK_STS_RESOURCE_OK:
> *cookie = new_cookie;
> return;
> case BLK_STS_RESOURCE:
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 7f218ef61900..0165c1caed82 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -2030,9 +2030,17 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
> case BLK_STS_OK:
> break;
> case BLK_STS_RESOURCE:
> + /*
> + * We have to insert the rq back before checking .device_busy,
> + * otherwise when IO completes just after the check and before
> + * this req is added to hctx->dispatch, this queue may never get
> + * chance to be run, then this IO may hang forever.
> + */
> + blk_mq_reinsert_request_hctx(hctx, req);
> if (atomic_read(&sdev->device_busy) == 0 &&
> !scsi_device_blocked(sdev))
> blk_mq_delay_run_hw_queue(hctx, SCSI_QUEUE_DELAY);
> + ret = BLK_STS_RESOURCE_OK;
> break;
> default:
> /*
> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
> index e5e6becd57d3..4740f643d8c5 100644
> --- a/include/linux/blk-mq.h
> +++ b/include/linux/blk-mq.h
> @@ -244,6 +244,7 @@ void blk_mq_start_request(struct request *rq);
> void blk_mq_end_request(struct request *rq, blk_status_t error);
> void __blk_mq_end_request(struct request *rq, blk_status_t error);
>
> +void blk_mq_reinsert_request_hctx(struct blk_mq_hw_ctx *hctx, struct request *rq);
> void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list);
> void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
> bool kick_requeue_list);
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 3385c89f402e..b630cc026a93 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -32,6 +32,7 @@ typedef u8 __bitwise blk_status_t;
> #define BLK_STS_PROTECTION ((__force blk_status_t)8)
> #define BLK_STS_RESOURCE ((__force blk_status_t)9)
> #define BLK_STS_IOERR ((__force blk_status_t)10)
> +#define BLK_STS_RESOURCE_OK ((__force blk_status_t)11)
>
> /* hack for device mapper, don't use elsewhere: */
> #define BLK_STS_DM_REQUEUE ((__force blk_status_t)11)
Running test one with this patch applied on top of Jens' for-next branch yields
the same result as without this patch:
[ ... ]
Error: unloading kernel module ib_srp failed
Test /home/bart/software/infiniband/srp-test/tests/01 failed
# dmesg -c >/dev/null; echo w > /proc/sysrq-trigger; dmesg
[ 325.167295] sysrq: SysRq : Show Blocked State
[ 325.173612] task PC stack pid father
[ 325.181903] kworker/10:1 D 0 165 2 0x80000000
[ 325.189396] Workqueue: srp_remove srp_remove_work [ib_srp]
[ 325.196222] Call Trace:
[ 325.199622] __schedule+0x2fa/0xbb0
[ 325.204227] schedule+0x36/0x90
[ 325.208390] async_synchronize_cookie_domain+0x88/0x130
[ 325.214915] ? finish_wait+0x90/0x90
[ 325.219574] async_synchronize_full_domain+0x18/0x20
[ 325.225816] sd_remove+0x4d/0xc0 [sd_mod]
[ 325.230949] device_release_driver_internal+0x160/0x210
[ 325.237479] device_release_driver+0x12/0x20
[ 325.242904] bus_remove_device+0x100/0x180
[ 325.248163] device_del+0x1d8/0x340
[ 325.252735] __scsi_remove_device+0xfc/0x130
[ 325.258192] scsi_forget_host+0x25/0x70
[ 325.263173] scsi_remove_host+0x79/0x120
[ 325.268227] srp_remove_work+0x90/0x1d0 [ib_srp]
[ 325.274059] process_one_work+0x20a/0x660
[ 325.279243] worker_thread+0x3d/0x3b0
[ 325.284004] kthread+0x13a/0x150
[ 325.288232] ? process_one_work+0x660/0x660
[ 325.293575] ? kthread_create_on_node+0x40/0x40
[ 325.299334] ret_from_fork+0x27/0x40
[ 325.304002] kworker/5:1 D 0 180 2 0x80000000
[ 325.310768] Workqueue: kaluad alua_rtpg_work [scsi_dh_alua]
[ 325.317674] Call Trace:
[ 325.321047] __schedule+0x2fa/0xbb0
[ 325.325615] ? trace_hardirqs_on_caller+0xfb/0x190
[ 325.331612] schedule+0x36/0x90
[ 325.335797] schedule_timeout+0x22c/0x570
[ 325.340917] ? call_timer_fn+0x330/0x330
[ 325.345972] ? wait_for_completion_io_timeout+0xf7/0x180
[ 325.352558] io_schedule_timeout+0x1e/0x50
[ 325.357808] ? io_schedule_timeout+0x1e/0x50
[ 325.363262] wait_for_completion_io_timeout+0x11f/0x180
[ 325.369793] ? wake_up_q+0x80/0x80
[ 325.374267] blk_execute_rq+0x86/0xc0
[ 325.379012] scsi_execute+0xdb/0x1f0
[ 325.383678] alua_rtpg_work+0x2b3/0xe8a [scsi_dh_alua]
[ 325.390130] process_one_work+0x20a/0x660
[ 325.395818] worker_thread+0x3d/0x3b0
[ 325.401248] kthread+0x13a/0x150
[ 325.406056] ? process_one_work+0x660/0x660
[ 325.412070] ? kthread_create_on_node+0x40/0x40
[ 325.418474] ret_from_fork+0x27/0x40
[ 325.423874] kworker/u66:1 D 0 331 2 0x80000000
[ 325.431374] Workqueue: events_unbound async_run_entry_fn
[ 325.438651] Call Trace:
[ 325.442662] __schedule+0x2fa/0xbb0
[ 325.447835] ? trace_hardirqs_on_caller+0xfb/0x190
[ 325.454522] schedule+0x36/0x90
[ 325.459339] schedule_timeout+0x22c/0x570
[ 325.465097] ? call_timer_fn+0x330/0x330
[ 325.470800] ? wait_for_completion_io_timeout+0xf7/0x180
[ 325.478017] io_schedule_timeout+0x1e/0x50
[ 325.483935] ? io_schedule_timeout+0x1e/0x50
[ 325.490015] wait_for_completion_io_timeout+0x11f/0x180
[ 325.497134] ? wake_up_q+0x80/0x80
[ 325.502272] blk_execute_rq+0x86/0xc0
[ 325.507652] scsi_execute+0xdb/0x1f0
[ 325.512960] sd_revalidate_disk+0xed/0x1c70 [sd_mod]
[ 325.519846] sd_probe_async+0xc3/0x1d0 [sd_mod]
[ 325.526199] async_run_entry_fn+0x38/0x160
[ 325.532121] process_one_work+0x20a/0x660
[ 325.537897] worker_thread+0x3d/0x3b0
[ 325.543319] kthread+0x13a/0x150
[ 325.548200] ? process_one_work+0x660/0x660
[ 325.554204] ? kthread_create_on_node+0x40/0x40
[ 325.560605] ret_from_fork+0x27/0x40
