linux-kernel - [PATCH v3 15/16] nvmet-fc: avoid deadlock on delete association path

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Message-ID: <20231218153105.12717-16-dwagner@suse.de>
Date: Mon, 18 Dec 2023 16:31:03 +0100
From: Daniel Wagner <dwagner@...e.de>
To: linux-nvme@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@....de>,
	Sagi Grimberg <sagi@...mberg.me>,
	Keith Busch <kbusch@...nel.org>,
	James Smart <james.smart@...adcom.com>,
	Hannes Reinecke <hare@...e.de>,
	Daniel Wagner <dwagner@...e.de>
Subject: [PATCH v3 15/16] nvmet-fc: avoid deadlock on delete association path

When deleting an association the shutdown path is deadlocking because we
try to flush the nvmet_wq nested. Avoid this by deadlock by deferring
the put work into its own work item.

Signed-off-by: Daniel Wagner <dwagner@...e.de>
---
 drivers/nvme/target/fc.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
index 23d8779dc221..30ba4ede333f 100644
--- a/drivers/nvme/target/fc.c
+++ b/drivers/nvme/target/fc.c
@@ -111,6 +111,8 @@ struct nvmet_fc_tgtport {
 	struct nvmet_fc_port_entry	*pe;
 	struct kref			ref;
 	u32				max_sg_cnt;
+
+	struct work_struct		put_work;
 };
 
 struct nvmet_fc_port_entry {
@@ -243,6 +245,13 @@ static LIST_HEAD(nvmet_fc_portentry_list);
 
 static void nvmet_fc_handle_ls_rqst_work(struct work_struct *work);
 static void nvmet_fc_fcp_rqst_op_defer_work(struct work_struct *work);
+static void nvmet_fc_put_tgtport_work(struct work_struct *work)
+{
+	struct nvmet_fc_tgtport *tgtport =
+		container_of(work, struct nvmet_fc_tgtport, put_work);
+
+	nvmet_fc_tgtport_put(tgtport);
+}
 static void nvmet_fc_tgt_a_put(struct nvmet_fc_tgt_assoc *assoc);
 static int nvmet_fc_tgt_a_get(struct nvmet_fc_tgt_assoc *assoc);
 static void nvmet_fc_tgt_q_put(struct nvmet_fc_tgt_queue *queue);
@@ -359,7 +368,7 @@ __nvmet_fc_finish_ls_req(struct nvmet_fc_ls_req_op *lsop)
 
 	if (!lsop->req_queued) {
 		spin_unlock_irqrestore(&tgtport->lock, flags);
-		nvmet_fc_tgtport_put(tgtport);
+		queue_work(nvmet_wq, &tgtport->put_work);
 		return;
 	}
 
@@ -373,7 +382,7 @@ __nvmet_fc_finish_ls_req(struct nvmet_fc_ls_req_op *lsop)
 				  (lsreq->rqstlen + lsreq->rsplen),
 				  DMA_BIDIRECTIONAL);
 
-	nvmet_fc_tgtport_put(tgtport);
+	queue_work(nvmet_wq, &tgtport->put_work);
 }
 
 static int
@@ -1402,6 +1411,7 @@ nvmet_fc_register_targetport(struct nvmet_fc_port_info *pinfo,
 	kref_init(&newrec->ref);
 	ida_init(&newrec->assoc_cnt);
 	newrec->max_sg_cnt = template->max_sgl_segments;
+	INIT_WORK(&newrec->put_work, nvmet_fc_put_tgtport_work);
 
 	ret = nvmet_fc_alloc_ls_iodlist(newrec);
 	if (ret) {
-- 
2.43.0