nvme-tcp: fix I/O stalls on congested sockets

When the socket is busy processing nvme_tcp_try_recv() might return
-EAGAIN, but this doesn't automatically imply that the sending side is
blocked, too.  So check if there are pending requests once
nvme_tcp_try_recv() returns -EAGAIN and continue with the sending loop
to avoid I/O stalls.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Acked-by: Chris Leech <cleech@redhat.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index b37028320edd46b398f3940eb5aeb4c64b20363b..abf78dc27e8407a545553c20ffc4751e792adfab 100644 (file)
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1361,7 +1361,7 @@ static int nvme_tcp_try_recv(struct nvme_tcp_queue *queue)
        queue->nr_cqe = 0;
        consumed = sock->ops->read_sock(sk, &rd_desc, nvme_tcp_recv_skb);
        release_sock(sk);
-       return consumed;
+       return consumed == -EAGAIN ? 0 : consumed;
 }
 
 static void nvme_tcp_io_work(struct work_struct *w)
@@ -1389,6 +1389,11 @@ 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;