[PATCH v2 1/1] nvme-tcp: wait socket wmem to drain in queue stop

[Michael Liang <mliang@purestorage.com>]

This patch addresses a data corruption issue observed in nvme-tcp during
testing.

Issue description:
In an NVMe native multipath setup, when an I/O timeout occurs, all inflight
I/Os are canceled almost immediately after the kernel socket is shut down.
These canceled I/Os are reported as host path errors, triggering a failover
that succeeds on a different path.

However, at this point, the original I/O may still be outstanding in the
host's network transmission path (e.g., the NIC’s TX queue). From the
user-space app's perspective, the buffer associated with the I/O is considered
completed since they're acked on the different path and may be reused for new
I/O requests.

Because nvme-tcp enables zero-copy by default in the transmission path,
this can lead to corrupted data being sent to the original target, ultimately
causing data corruption.

We can reproduce this data corruption by injecting delay on one path and
triggering i/o timeout.

To prevent this issue, this change ensures that all inflight transmissions are
fully completed from host's perspective before returning from queue
stop. To handle concurrent I/O timeout from multiple namespaces under
the same controller, always wait in queue stop regardless of queue's state.

This aligns with the behavior of queue stopping in other NVMe fabric transports.

Reviewed-by: Mohamed Khalfella <mkhalfella@purestorage.com>
Reviewed-by: Randy Jennings <randyj@purestorage.com>
Signed-off-by: Michael Liang <mliang@purestorage.com>
---
 drivers/nvme/host/tcp.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 26c459f0198d..62d73684e61e 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1944,6 +1944,21 @@ static void __nvme_tcp_stop_queue(struct nvme_tcp_queue *queue)
 	cancel_work_sync(&queue->io_work);
 }
 
+static void nvme_tcp_stop_queue_wait(struct nvme_tcp_queue *queue)
+{
+	int timeout = 100;
+
+	while (timeout > 0) {
+		if (!sk_wmem_alloc_get(queue->sock->sk))
+			return;
+		msleep(2);
+		timeout -= 2;
+	}
+	dev_warn(queue->ctrl->ctrl.device,
+		 "qid %d: wait draining sock wmem allocation timeout\n",
+		 nvme_tcp_queue_id(queue));
+}
+
 static void nvme_tcp_stop_queue(struct nvme_ctrl *nctrl, int qid)
 {
 	struct nvme_tcp_ctrl *ctrl = to_tcp_ctrl(nctrl);
@@ -1961,6 +1976,7 @@ static void nvme_tcp_stop_queue(struct nvme_ctrl *nctrl, int qid)
 	/* Stopping the queue will disable TLS */
 	queue->tls_enabled = false;
 	mutex_unlock(&queue->queue_lock);
+	nvme_tcp_stop_queue_wait(queue);
 }
 
 static void nvme_tcp_setup_sock_ops(struct nvme_tcp_queue *queue)
-- 
2.34.1