nvmet: use a private workqueue instead of the system workqueue

Any attempt to flush kernel-global WQs has possibility of deadlock
so we should simply stop using them, instead introduce nvmet_wq
which is the generic nvmet workqueue for work elements that
don't explicitly require a dedicated workqueue (by the mere fact
that they are using the system_wq).

Changes were done using the following replaces:

 - s/schedule_work(/queue_work(nvmet_wq, /g
 - s/schedule_delayed_work(/queue_delayed_work(nvmet_wq, /g
 - s/flush_scheduled_work()/flush_workqueue(nvmet_wq)/g

Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 18 insertions, 6 deletions

diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 92af37d33ec3..cd833b1dd47c 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -20,6 +20,9 @@ struct workqueue_struct *zbd_wq;
 static const struct nvmet_fabrics_ops *nvmet_transports[NVMF_TRTYPE_MAX];
 static DEFINE_IDA(cntlid_ida);
 
+struct workqueue_struct *nvmet_wq;
+EXPORT_SYMBOL_GPL(nvmet_wq);
+
 /*
  * This read/write semaphore is used to synchronize access to configuration
  * information on a target system that will result in discovery log page
@@ -205,7 +208,7 @@ void nvmet_add_async_event(struct nvmet_ctrl *ctrl, u8 event_type,
 	list_add_tail(&aen->entry, &ctrl->async_events);
 	mutex_unlock(&ctrl->lock);
 
-	schedule_work(&ctrl->async_event_work);
+	queue_work(nvmet_wq, &ctrl->async_event_work);
 }
 
 static void nvmet_add_to_changed_ns_log(struct nvmet_ctrl *ctrl, __le32 nsid)
@@ -385,7 +388,7 @@ static void nvmet_keep_alive_timer(struct work_struct *work)
 	if (reset_tbkas) {
 		pr_debug("ctrl %d reschedule traffic based keep-alive timer\n",
 			ctrl->cntlid);
-		schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
+		queue_delayed_work(nvmet_wq, &ctrl->ka_work, ctrl->kato * HZ);
 		return;
 	}
 
@@ -403,7 +406,7 @@ void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl)
 	pr_debug("ctrl %d start keep-alive timer for %d secs\n",
 		ctrl->cntlid, ctrl->kato);
 
-	schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
+	queue_delayed_work(nvmet_wq, &ctrl->ka_work, ctrl->kato * HZ);
 }
 
 void nvmet_stop_keep_alive_timer(struct nvmet_ctrl *ctrl)
@@ -1478,7 +1481,7 @@ void nvmet_ctrl_fatal_error(struct nvmet_ctrl *ctrl)
 	mutex_lock(&ctrl->lock);
 	if (!(ctrl->csts & NVME_CSTS_CFS)) {
 		ctrl->csts |= NVME_CSTS_CFS;
-		schedule_work(&ctrl->fatal_err_work);
+		queue_work(nvmet_wq, &ctrl->fatal_err_work);
 	}
 	mutex_unlock(&ctrl->lock);
 }
@@ -1620,9 +1623,15 @@ static int __init nvmet_init(void)
 		goto out_free_zbd_work_queue;
 	}
 
+	nvmet_wq = alloc_workqueue("nvmet-wq", WQ_MEM_RECLAIM, 0);
+	if (!nvmet_wq) {
+		error = -ENOMEM;
+		goto out_free_buffered_work_queue;
+	}
+
 	error = nvmet_init_discovery();
 	if (error)
-		goto out_free_work_queue;
+		goto out_free_nvmet_work_queue;
 
 	error = nvmet_init_configfs();
 	if (error)
@@ -1631,7 +1640,9 @@ static int __init nvmet_init(void)
 
 out_exit_discovery:
 	nvmet_exit_discovery();
-out_free_work_queue:
+out_free_nvmet_work_queue:
+	destroy_workqueue(nvmet_wq);
+out_free_buffered_work_queue:
 	destroy_workqueue(buffered_io_wq);
 out_free_zbd_work_queue:
 	destroy_workqueue(zbd_wq);
@@ -1643,6 +1654,7 @@ static void __exit nvmet_exit(void)
 	nvmet_exit_configfs();
 	nvmet_exit_discovery();
 	ida_destroy(&cntlid_ida);
+	destroy_workqueue(nvmet_wq);
 	destroy_workqueue(buffered_io_wq);
 	destroy_workqueue(zbd_wq);