linux-kernel - [PATCH v3 2/4] nvmet-loop: Flush nvme_delete

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Message-Id: <20190731233534.4841-3-logang@deltatee.com>
Date:   Wed, 31 Jul 2019 17:35:32 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org
Cc:     Christoph Hellwig <hch@....de>, Keith Busch <kbusch@...nel.org>,
        Jens Axboe <axboe@...com>, Sagi Grimberg <sagi@...mberg.me>,
        Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH v3 2/4] nvmet-loop: Flush nvme_delete_wq when removing the port

After calling nvme_loop_delete_ctrl(), the controllers will not
yet be deleted because nvme_delete_ctrl() only schedules work
to do the delete.

This means a race can occur if a port is removed but there
are still active controllers trying to access that memory.

To fix this, flush the nvme_delete_wq before returning from
nvme_loop_remove_port() so that any controllers that might
be in the process of being deleted won't access a freed port.

Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
Reviewed-by: Sagi Grimberg <sagi@...mberg.me>
Reviewed-by: Max Gurtovoy <maxg@...lanox.com>
---
 drivers/nvme/target/loop.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/nvme/target/loop.c b/drivers/nvme/target/loop.c
index b16dc3981c69..0940c5024a34 100644
--- a/drivers/nvme/target/loop.c
+++ b/drivers/nvme/target/loop.c
@@ -654,6 +654,14 @@ static void nvme_loop_remove_port(struct nvmet_port *port)
 	mutex_lock(&nvme_loop_ports_mutex);
 	list_del_init(&port->entry);
 	mutex_unlock(&nvme_loop_ports_mutex);
+
+	/*
+	 * Ensure any ctrls that are in the process of being
+	 * deleted are in fact deleted before we return
+	 * and free the port. This is to prevent active
+	 * ctrls from using a port after it's freed.
+	 */
+	flush_workqueue(nvme_delete_wq);
 }
 
 static const struct nvmet_fabrics_ops nvme_loop_ops = {
-- 
2.20.1