linux-kernel - Re: [PATCH net-next v7 3/5] net: devmem: implement autorelease token management

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Message-ID: <aR80PvXaX1+S/avE@devvm11784.nha0.facebook.com>
Date: Thu, 20 Nov 2025 07:31:10 -0800
From: Bobby Eshleman <bobbyeshleman@...il.com>
To: Paolo Abeni <pabeni@...hat.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Simon Horman <horms@...nel.org>,
	Kuniyuki Iwashima <kuniyu@...gle.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	David Ahern <dsahern@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Jonathan Corbet <corbet@....net>,
	Andrew Lunn <andrew+netdev@...n.ch>, Shuah Khan <shuah@...nel.org>,
	Donald Hunter <donald.hunter@...il.com>,
	Mina Almasry <almasrymina@...gle.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
	Stanislav Fomichev <sdf@...ichev.me>,
	Bobby Eshleman <bobbyeshleman@...a.com>
Subject: Re: [PATCH net-next v7 3/5] net: devmem: implement autorelease token
 management

On Thu, Nov 20, 2025 at 01:19:54PM +0100, Paolo Abeni wrote:
> On 11/20/25 4:37 AM, Bobby Eshleman wrote:
> > @@ -2479,10 +2504,12 @@ static int tcp_recvmsg_dmabuf(struct sock *sk, const struct sk_buff *skb,
> >  			      unsigned int offset, struct msghdr *msg,
> >  			      int remaining_len)
> >  {
> > +	struct net_devmem_dmabuf_binding *binding = NULL;
> >  	struct dmabuf_cmsg dmabuf_cmsg = { 0 };
> >  	struct tcp_xa_pool tcp_xa_pool;
> >  	unsigned int start;
> >  	int i, copy, n;
> > +	int refs = 0;
> >  	int sent = 0;
> >  	int err = 0;
> >  
> > @@ -2536,6 +2563,7 @@ static int tcp_recvmsg_dmabuf(struct sock *sk, const struct sk_buff *skb,
> >  			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
> >  			struct net_iov *niov;
> >  			u64 frag_offset;
> > +			u32 token;
> >  			int end;
> >  
> >  			/* !skb_frags_readable() should indicate that ALL the
> > @@ -2568,13 +2596,32 @@ static int tcp_recvmsg_dmabuf(struct sock *sk, const struct sk_buff *skb,
> >  					      start;
> >  				dmabuf_cmsg.frag_offset = frag_offset;
> >  				dmabuf_cmsg.frag_size = copy;
> > -				err = tcp_xa_pool_refill(sk, &tcp_xa_pool,
> > -							 skb_shinfo(skb)->nr_frags - i);
> > -				if (err)
> > +
> > +				binding = net_devmem_iov_binding(niov);
> > +
> > +				if (!sk->sk_devmem_info.binding)
> > +					sk->sk_devmem_info.binding = binding;
> > +
> > +				if (sk->sk_devmem_info.binding != binding) {
> > +					err = -EFAULT;
> >  					goto out;
> > +				}
> > +
> > +				if (static_branch_unlikely(&tcp_devmem_ar_key)) {
> 
> Not a real/full review but the above is apparently causing kunit build
> failures:
> 
> ERROR:root:ld: vmlinux.o: in function `tcp_recvmsg_dmabuf':
> tcp.c:(.text+0x669b21): undefined reference to `tcp_devmem_ar_key'
> ld: tcp.c:(.text+0x669b68): undefined reference to `tcp_devmem_ar_key'
> ld: tcp.c:(.text+0x669c54): undefined reference to `tcp_devmem_ar_key'
> make[3]: *** [../scripts/Makefile.vmlinux:72: vmlinux.unstripped] Error 1
> make[2]: *** [/home/kunit/testing/Makefile:1242: vmlinux] Error 2
> make[1]: *** [/home/kunit/testing/Makefile:248: __sub-make] Error 2
> make: *** [Makefile:248: __sub-make] Error 2
> 
> see:
> 
> https://netdev-3.bots.linux.dev/kunit/results/393664/

Thanks Paolo, I'll fix that for the next rev. And I'll have to add
building kunit into my flow (currently using some custom stuff and nipa
ingest_mdir, but don't think either has kunit).
> 
> > @@ -2617,6 +2664,7 @@ static int tcp_recvmsg_dmabuf(struct sock *sk,
> > const struct sk_buff *skb,
> >  
> >  out: tcp_xa_pool_commit(sk, &tcp_xa_pool); +
> 
> [just because I stumbled upon the above while looking for the build
> issue]: please do not mix unrelated whitespace-change only with
> functional change.

Don't know how I missed that line, will definitely remove.

Thanks again,
Bobby