Re: [PATCH 4/4] net/tls: implement ->read_sock()

Sagi Grimberg
2023-06-20T13:21:33Z

> Implement ->read_sock() function for use with nvme-tcp.
>
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
> Cc: Boris Pismenny <boris.pismenny@gmail.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: netdev@vger.kernel.org
> ---
> net/tls/tls.h | 2 ++
> net/tls/tls_main.c | 2 ++
> net/tls/tls_sw.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 82 insertions(+)
>
> diff --git a/net/tls/tls.h b/net/tls/tls.h
> index d002c3af1966..ba55cd5c4913 100644
> --- a/net/tls/tls.h
> +++ b/net/tls/tls.h
> @@ -114,6 +114,8 @@ bool tls_sw_sock_is_readable(struct sock *sk);
> ssize_t tls_sw_splice_read(struct socket *sock, loff_t *ppos,
> struct pipe_inode_info *pipe,
> size_t len, unsigned int flags);
> +int tls_sw_read_sock(struct sock *sk, read_descriptor_t *desc,
> + sk_read_actor_t read_actor);
>
> int tls_device_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
> void tls_device_splice_eof(struct socket *sock);
> diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
> index 7b9c83dd7de2..1a062a8c6d33 100644
> --- a/net/tls/tls_main.c
> +++ b/net/tls/tls_main.c
> @@ -963,10 +963,12 @@ static void build_proto_ops(struct proto_ops ops[TLS_NUM_CONFIG][TLS_NUM_CONFIG]
> ops[TLS_BASE][TLS_SW ] = ops[TLS_BASE][TLS_BASE];
> ops[TLS_BASE][TLS_SW ].splice_read = tls_sw_splice_read;
> ops[TLS_BASE][TLS_SW ].poll = tls_sk_poll;
> + ops[TLS_BASE][TLS_SW ].read_sock = tls_sw_read_sock;
>
> ops[TLS_SW ][TLS_SW ] = ops[TLS_SW ][TLS_BASE];
> ops[TLS_SW ][TLS_SW ].splice_read = tls_sw_splice_read;
> ops[TLS_SW ][TLS_SW ].poll = tls_sk_poll;
> + ops[TLS_SW ][TLS_SW ].read_sock = tls_sw_read_sock;
>
> #ifdef CONFIG_TLS_DEVICE
> ops[TLS_HW ][TLS_BASE] = ops[TLS_BASE][TLS_BASE];
> diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
> index 97379e34c997..e918c98bbeb2 100644
> --- a/net/tls/tls_sw.c
> +++ b/net/tls/tls_sw.c
> @@ -2231,6 +2231,84 @@ ssize_t tls_sw_splice_read(struct socket *sock, loff_t *ppos,
> goto splice_read_end;
> }
>
> +int tls_sw_read_sock(struct sock *sk, read_descriptor_t *desc,
> + sk_read_actor_t read_actor)
> +{
> + struct tls_context *tls_ctx = tls_get_ctx(sk);
> + struct tls_sw_context_rx *ctx = tls_sw_ctx_rx(tls_ctx);
> + struct strp_msg *rxm = NULL;
> + struct tls_msg *tlm;
> + struct sk_buff *skb;
> + ssize_t copied = 0;
> + int err, used;
> +
> + err = tls_rx_reader_lock(sk, ctx, true);
> + if (err < 0)
> + return err;

Unlike recvmsg or splice_read, the caller of read_sock is assumed to
have the socket locked, and tls_rx_reader_lock also calls lock_sock,
how is this not a deadlock?

I'm not exactly clear why the lock is needed here or what is the subtle
distinction between tls_rx_reader_lock and what lock_sock provides.