netdev - Re: kTLS in combination with mlx4 is very unstable

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Message-ID: <20180501160908.GA26223@advait-mbp.dhcp.thefacebook.com>
Date:   Tue, 1 May 2018 09:09:08 -0700
From:   Dave Watson <davejwatson@...com>
To:     Andre Tomt <andre@...t.net>
CC:     netdev <netdev@...r.kernel.org>, <borisp@...lanox.com>,
        Aviad Yehezkel <aviadye@...lanox.com>
Subject: Re: kTLS in combination with mlx4 is very unstable

Hi Andre, 

On 04/24/18 10:01 AM, Dave Watson wrote:
> On 04/22/18 11:21 PM, Andre Tomt wrote:
> > The kernel seems to get increasingly unstable as I load it up with client
> > connections. At about 9Gbps and 700 connections, it is okay at least for a
> > while - it might run fine for say 45 minutes. Once it gets to 20 - 30Gbps,
> > the kernel will usually start spewing OOPSes within minutes and the traffic
> > drops.
> > 
> > Some bad interaction between mlx4 and kTLS?

I tried to repro, but wasn't able to - of course I don't have an mlx4
test setup.  If I manually add a tls_write_space call after
do_tcp_sendpages, I get a similar stack though.

Something like the following should work, can you test?  Thanks

diff --git a/include/net/tls.h b/include/net/tls.h
index 8c56809..ee78f33 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -187,6 +187,7 @@ struct tls_context {
        struct scatterlist *partially_sent_record;
        u16 partially_sent_offset;
        unsigned long flags;
+       bool in_tcp_sendpages;
 
        u16 pending_open_record_frags;
        int (*push_pending_record)(struct sock *sk, int flags);
diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index 3aafb87..095af65 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -114,6 +114,7 @@ int tls_push_sg(struct sock *sk,
        size = sg->length - offset;
        offset += sg->offset;
 
+       ctx->in_tcp_sendpages = 1;
        while (1) {
                if (sg_is_last(sg))
                        sendpage_flags = flags;
@@ -148,6 +149,8 @@ int tls_push_sg(struct sock *sk,
        }
 
        clear_bit(TLS_PENDING_CLOSED_RECORD, &ctx->flags);
+       ctx->in_tcp_sendpages = 0;
+       ctx->sk_write_space(sk);
 
        return 0;
 }
@@ -217,6 +220,9 @@ static void tls_write_space(struct sock *sk)
 {
        struct tls_context *ctx = tls_get_ctx(sk);
 
+       if (ctx->in_tcp_sendpages)
+               return;
+
        if (!sk->sk_write_pending && tls_is_pending_closed_record(ctx)) {
                gfp_t sk_allocation = sk->sk_allocation;
                int rc;