linux-kernel - [PATCH AUTOSEL for 4.14 022/100] nvmet-fc: correct ref counting error when deferred rcv used

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Message-ID: <20180124041414.32065-22-alexander.levin@microsoft.com>
Date:   Wed, 24 Jan 2018 04:14:33 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     James Smart <jsmart2021@...il.com>,
        James Smart <james.smart@...adcom.com>,
        Christoph Hellwig <hch@....de>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.14 022/100] nvmet-fc: correct ref counting error
 when deferred rcv used

From: James Smart <jsmart2021@...il.com>

[ Upstream commit 619c62dcc62b957d17cccde2081cad527b020883 ]

Whenever a cmd is received a reference is taken while looking up the
queue. The reference is removed after the cmd is done as the iod is
returned for reuse. The fod may be reused for a deferred (recevied but
no job context) cmd.  Existing code removes the reference only if the
fod is not reused for another command. Given the fod may be used for
one or more ios, although a reference was taken per io, it won't be
matched on the frees.

Remove the reference on every fod free. This pairs the references to
each io.

Signed-off-by: James Smart <james.smart@...adcom.com>
Reviewed-by: Sagi Grimberg <sagi@...mberg.me>
Signed-off-by: Christoph Hellwig <hch@....de>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/nvme/target/fc.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
index 58e010bdda3e..8e21211b904b 100644
--- a/drivers/nvme/target/fc.c
+++ b/drivers/nvme/target/fc.c
@@ -532,15 +532,15 @@ nvmet_fc_free_fcp_iod(struct nvmet_fc_tgt_queue *queue,
 
 	tgtport->ops->fcp_req_release(&tgtport->fc_target_port, fcpreq);
 
+	/* release the queue lookup reference on the completed IO */
+	nvmet_fc_tgt_q_put(queue);
+
 	spin_lock_irqsave(&queue->qlock, flags);
 	deferfcp = list_first_entry_or_null(&queue->pending_cmd_list,
 				struct nvmet_fc_defer_fcp_req, req_list);
 	if (!deferfcp) {
 		list_add_tail(&fod->fcp_list, &fod->queue->fod_list);
 		spin_unlock_irqrestore(&queue->qlock, flags);
-
-		/* Release reference taken at queue lookup and fod allocation */
-		nvmet_fc_tgt_q_put(queue);
 		return;
 	}
 
@@ -759,6 +759,9 @@ nvmet_fc_delete_target_queue(struct nvmet_fc_tgt_queue *queue)
 		tgtport->ops->fcp_req_release(&tgtport->fc_target_port,
 				deferfcp->fcp_req);
 
+		/* release the queue lookup reference */
+		nvmet_fc_tgt_q_put(queue);
+
 		kfree(deferfcp);
 
 		spin_lock_irqsave(&queue->qlock, flags);
-- 
2.11.0