[PATCH 3/3] nvme-tcp: fix I/O stalls on congested sockets

[Kamaljit Singh]

Sagi,

>>
>> Right after the check sk_stream_is_writeable(), there could have new
>> room in the socket
>> send buffer, state_change() fired, and queued io_work, before we get
>> to the pending
>> check. This is the "lost event" problem.
>
>Actually, this is incorrect. write_space() -> queue_work(io_work) will
>be re-queued if io_work
>is currently running. Hence I'm not sure that this flag is needed.
>
>Kamaljit, can you run with the below and report if it fixes your problem?
With the last set of fixes that included list_del_init() you suggested, all
tests have been stable. I'm not seeing any more issues. Are you asking to
test this patch regardless? If so, does this need to be in addition to
previous patches?


>--
>diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
>index 4d20fcc0a230..835e29014841 100644
>--- a/drivers/nvme/host/tcp.c
>+++ b/drivers/nvme/host/tcp.c
>@@ -1390,6 +1390,11 @@ static void nvme_tcp_io_work(struct work_struct *w)
>                 else if (unlikely(result < 0))
>                         return;
>
>+               /* did we get some space after spending time in recv? */
>+               if (nvme_tcp_queue_has_pending(queue) &&
>+                   sk_stream_is_writeable(queue->sock->sk))
>+                       pending = true;
>+
>                 if (!pending || !queue->rd_enabled)
>                         return;
>--

Thanks,
Kamaljit