netdev - Re: [PATCH net-next v10 08/16] tls: Inline do_tcp

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Date: Thu, 3 Aug 2023 14:47:35 +0300
From: Tariq Toukan <ttoukan.linux@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: David Howells <dhowells@...hat.com>, netdev@...r.kernel.org,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>,
 Willem de Bruijn <willemdebruijn.kernel@...il.com>,
 David Ahern <dsahern@...nel.org>, Matthew Wilcox <willy@...radead.org>,
 Al Viro <viro@...iv.linux.org.uk>, Christoph Hellwig <hch@...radead.org>,
 Jens Axboe <axboe@...nel.dk>, Jeff Layton <jlayton@...nel.org>,
 Christian Brauner <brauner@...nel.org>,
 Chuck Lever III <chuck.lever@...cle.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, Boris Pismenny <borisp@...dia.com>,
 John Fastabend <john.fastabend@...il.com>, Gal Pressman <gal@...dia.com>,
 ranro@...dia.com, samiram@...dia.com, drort@...dia.com,
 Tariq Toukan <tariqt@...dia.com>
Subject: Re: [PATCH net-next v10 08/16] tls: Inline do_tcp_sendpages()

On 26/07/2023 3:30, Jakub Kicinski wrote:
> On Sun, 23 Jul 2023 09:35:56 +0300 Tariq Toukan wrote:
>> Hi Jakub, David,
>>
>> We repro the issue on the server side using this client command:
>> $ wrk -b2.2.2.2 -t4 -c1000 -d5 --timeout 5s
>> https://2.2.2.3:20443/256000b.img
>>
>> Port 20443 is configured with:
>>       ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256;
>>       sendfile    off;
>>
>>
>> Important:
>> 1. Couldn't repro with files smaller than 40KB.
>> 2. Couldn't repro with "sendfile    on;"
>>
>> In addition, we collected the vmcore (forced by panic_on_warn), it can
>> be downloaded from here:
>> https://drive.google.com/file/d/1Fi2dzgq6k2hb2L_kwyntRjfLF6_RmbxB/view?usp=sharing
> 
> This has no symbols :(
> 
> There is a small bug in this commit, we should always set SPLICE.
> But I don't see how that'd cause the warning you're seeing.
> Does your build have CONFIG_DEBUG_VM enabled?
> 
> -->8-------------------------
> 
> From: Jakub Kicinski <kuba@...nel.org>
> Date: Tue, 25 Jul 2023 17:03:25 -0700
> Subject: net: tls: set MSG_SPLICE_PAGES consistently
> 
> We used to change the flags for the last segment, because
> non-last segments had the MSG_SENDPAGE_NOTLAST flag set.
> That flag is no longer a thing so remove the setting.
> 
> Since flags most likely don't have MSG_SPLICE_PAGES set
> this avoids passing parts of the sg as splice and parts
> as non-splice.
> 
> ... tags ...
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
>   net/tls/tls_main.c | 3 ---
>   1 file changed, 3 deletions(-)
> 
> diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
> index b6896126bb92..4a8ee2f6badb 100644
> --- a/net/tls/tls_main.c
> +++ b/net/tls/tls_main.c
> @@ -139,9 +139,6 @@ int tls_push_sg(struct sock *sk,
>   
>   	ctx->splicing_pages = true;
>   	while (1) {
> -		if (sg_is_last(sg))
> -			msg.msg_flags = flags;
> -
>   		/* is sending application-limited? */
>   		tcp_rate_check_app_limited(sk);
>   		p = sg_page(sg);

Hi Jakub,

When applying this patch, repro disappears! :)
Apparently it is related to the warning.
Please go on and submit it.

Tested-by: Tariq Toukan <tariqt@...dia.com>

We are going to run more comprehensive tests, I'll let you know if we 
find anything unusual.

Regards,
Tariq