linux-kernel - Re: [PATCH] nvme/tcp: handle tls partially sent records in write

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Message-ID: <0bf649d5-112f-42a8-bc8d-6ef2199ed19d@suse.de>
Date: Tue, 7 Oct 2025 07:19:32 +0200
From: Hannes Reinecke <hare@...e.de>
To: Wilfred Mallawa <wilfred.opensource@...il.com>,
 linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org
Cc: Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...nel.dk>,
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
 John Fastabend <john.fastabend@...il.com>, Jakub Kicinski <kuba@...nel.org>,
 Sabrina Dubroca <sd@...asysnail.net>, "David S . Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
 Wilfred Mallawa <wilfred.mallawa@....com>
Subject: Re: [PATCH] nvme/tcp: handle tls partially sent records in
 write_space()

On 10/7/25 02:46, Wilfred Mallawa wrote:
> From: Wilfred Mallawa <wilfred.mallawa@....com>
> 
> With TLS enabled, records that are encrypted and appended to TLS TX
> list can fail to see a retry if the underlying TCP socket is busy, for
> example, hitting an EAGAIN from tcp_sendmsg_locked(). This is not known
> to the NVMe TCP driver, as the TLS layer successfully generated a record.
> 
> Typically, the TLS write_space() callback would ensure such records are
> retried, but in the NVMe TCP Host driver, write_space() invokes
> nvme_tcp_write_space(). This causes a partially sent record in the TLS TX
> list to timeout after not being retried.
> 
> This patch aims to address the above by first publically exposing
> tls_is_partially_sent_record(), then, using this in the NVMe TCP host
> driver to invoke the TLS write_space() handler where appropriate.
> 
> Signed-off-by: Wilfred Mallawa <wilfred.mallawa@....com>
> Fixes: be8e82caa685 ("nvme-tcp: enable TLS handshake upcall")
> ---
>   drivers/nvme/host/tcp.c | 8 ++++++++
>   include/net/tls.h       | 5 +++++
>   net/tls/tls.h           | 5 -----
>   3 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> index 1413788ca7d5..e3d02c33243b 100644
> --- a/drivers/nvme/host/tcp.c
> +++ b/drivers/nvme/host/tcp.c
> @@ -1076,11 +1076,18 @@ static void nvme_tcp_data_ready(struct sock *sk)
>   static void nvme_tcp_write_space(struct sock *sk)
>   {
>   	struct nvme_tcp_queue *queue;
> +	struct tls_context *ctx = tls_get_ctx(sk);
>   
>   	read_lock_bh(&sk->sk_callback_lock);
>   	queue = sk->sk_user_data;
> +
>   	if (likely(queue && sk_stream_is_writeable(sk))) {
>   		clear_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
> +		/* Ensure pending TLS partial records are retried */
> +		if (nvme_tcp_queue_tls(queue) &&
> +		    tls_is_partially_sent_record(ctx))
> +			queue->write_space(sk);
> +
>   		queue_work_on(queue->io_cpu, nvme_tcp_wq, &queue->io_work);
>   	}
>   	read_unlock_bh(&sk->sk_callback_lock);

I wonder: Do we really need to check for a partially assembled record,
or wouldn't it be easier to call queue->write_space() every time here?
We sure would end up with executing the callback more often, but if no
data is present it shouldn't do any harm.

IE just use

if (nvme_tcp_queue_tls(queue)
     queue->write_space(sk);

> @@ -1306,6 +1313,7 @@ static int nvme_tcp_try_send_ddgst(struct nvme_tcp_request *req)
>   static int nvme_tcp_try_send(struct nvme_tcp_queue *queue)
>   {
>   	struct nvme_tcp_request *req;
> +	struct tls_context *ctx = tls_get_ctx(queue->sock->sk);
>   	unsigned int noreclaim_flag;
>   	int ret = 1;
>   And we need this why?

> diff --git a/include/net/tls.h b/include/net/tls.h
> index 857340338b69..9c61a2de44bf 100644
> --- a/include/net/tls.h
> +++ b/include/net/tls.h
> @@ -373,6 +373,11 @@ static inline struct tls_context *tls_get_ctx(const struct sock *sk)
>   	return (__force void *)icsk->icsk_ulp_data;
>   }
>   
> +static inline bool tls_is_partially_sent_record(struct tls_context *ctx)
> +{
> +	return !!ctx->partially_sent_record;
> +}
> +
>   static inline struct tls_sw_context_rx *tls_sw_ctx_rx(
>   		const struct tls_context *tls_ctx)
>   {
> diff --git a/net/tls/tls.h b/net/tls/tls.h
> index 2f86baeb71fc..7839a2effe31 100644
> --- a/net/tls/tls.h
> +++ b/net/tls/tls.h
> @@ -271,11 +271,6 @@ int tls_push_partial_record(struct sock *sk, struct tls_context *ctx,
>   			    int flags);
>   void tls_free_partial_record(struct sock *sk, struct tls_context *ctx);
>   
> -static inline bool tls_is_partially_sent_record(struct tls_context *ctx)
> -{
> -	return !!ctx->partially_sent_record;
> -}
> -
>   static inline bool tls_is_pending_open_record(struct tls_context *tls_ctx)
>   {
>   	return tls_ctx->pending_open_record_frags;
See above. If we were calling ->write_space unconditionally we 
wouldn'teven need this export.Cheers,Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich