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

[Sagi Grimberg <sagi@grimberg.me>]

On 4/18/25 14:30, Sagi Grimberg wrote:
>
>
> On 4/17/25 10:13, Michael Liang wrote:
>> 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)
>
> This makes sense. But I do not want to pay this price serially.
> As the concern is just failover, lets do something like: diff --git 
> a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c index 
> 5041cbfd8272..d482a8fe2c4b 100644 --- a/drivers/nvme/host/tcp.c +++ 
> b/drivers/nvme/host/tcp.c @@ -2031,6 +2031,8 @@ static void 
> nvme_tcp_stop_io_queues(struct nvme_ctrl *ctrl) for (i = 1; i < 
> ctrl->queue_count; i++) nvme_tcp_stop_queue(ctrl, i); + for (i = 1; i 
> < ctrl->queue_count; i++) + 
> nvme_tcp_stop_queue_wait(&ctrl->queues[i]); } static int 
> nvme_tcp_start_io_queues(struct nvme_ctrl *ctrl, @@ -2628,8 +2630,10 
> @@ static void nvme_tcp_complete_timed_out(struct request *rq) { 
> struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq); struct nvme_ctrl 
> *ctrl = &req->queue->ctrl->ctrl; + int idx = 
> nvme_tcp_queue_id(req->queue); - nvme_tcp_stop_queue(ctrl, 
> nvme_tcp_queue_id(req->queue)); + nvme_tcp_stop_queue(ctrl, idx); + 
> nvme_tcp_stop_queue_wait(&ctrl->queues[idx]); 
> nvmf_complete_timed_out_request(rq); }

Or perhaps something like:
--
diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 5041cbfd8272..3e206a2cbbf3 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1944,7 +1944,7 @@ static void __nvme_tcp_stop_queue(struct 
nvme_tcp_queue *queue)
         cancel_work_sync(&queue->io_work);
  }

-static void nvme_tcp_stop_queue(struct nvme_ctrl *nctrl, int qid)
+static void nvme_tcp_stop_queue_nowait(struct nvme_ctrl *nctrl, int qid)
  {
         struct nvme_tcp_ctrl *ctrl = to_tcp_ctrl(nctrl);
         struct nvme_tcp_queue *queue = &ctrl->queues[qid];
@@ -1963,6 +1963,29 @@ static void nvme_tcp_stop_queue(struct nvme_ctrl 
*nctrl, int qid)
         mutex_unlock(&queue->queue_lock);
  }

+static void nvme_tcp_wait_queue(struct nvme_ctrl *nctrl, int qid)
+{
+       struct nvme_tcp_ctrl *ctrl = to_tcp_ctrl(nctrl);
+       struct nvme_tcp_queue *queue = ctrl->queues[qid];
+       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: timeout draining sock wmem allocation expired\n",
+                nvme_tcp_queue_id(queue));
+}
+
+static void nvme_tcp_stop_queue(struct nvme_ctrl *nctrl, int qid)
+{
+       nvme_tcp_stop_queue_nowait(nctrl, qid);
+       nvme_tcp_wait_queue(nctrl, qid);
+}
+
  static void nvme_tcp_setup_sock_ops(struct nvme_tcp_queue *queue)
  {
write_lock_bh(&queue->sock->sk->sk_callback_lock);
@@ -2030,7 +2053,9 @@ static void nvme_tcp_stop_io_queues(struct 
nvme_ctrl *ctrl)
         int i;

         for (i = 1; i < ctrl->queue_count; i++)
-               nvme_tcp_stop_queue(ctrl, i);
+               nvme_tcp_stop_queue_nowait(ctrl, i);
+       for (i = 1; i < ctrl->queue_count; i++)
+               nvme_tcp_wait_queue(ctrl, i);
  }

  static int nvme_tcp_start_io_queues(struct nvme_ctrl *ctrl,
--