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

[Chris Leech]

On Fri, Mar 07, 2025 at 02:28:02PM +0100, Hannes Reinecke wrote:
> 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 at kernel.org>
> ---

This looks good to me.

Acked-by: Chris Leech <cleech at redhat.com>

>  drivers/nvme/host/tcp.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> index 073c8c3538fd..d39d955bad99 100644
> --- a/drivers/nvme/host/tcp.c
> +++ b/drivers/nvme/host/tcp.c
> @@ -1357,9 +1357,12 @@ static void nvme_tcp_io_work(struct work_struct *w)
>  		result = nvme_tcp_try_recv(queue);
>  		if (result > 0)
>  			pending = true;
> -		else if (unlikely(result < 0))
> +		else if (unlikely(result < 0) && result != -EAGAIN)
>  			return;
>  
> +		if (nvme_tcp_queue_has_pending(queue))
> +			pending = true;
> +
>  		if (!pending || !queue->rd_enabled)
>  			return;
>  
> -- 
> 2.35.3
> 
>