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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <20230526201202.1cd35fe9@kernel.org>
References: <20230526201202.1cd35fe9@kernel.org> <20230524144923.3623536-1-dhowells@redhat.com> <20230524144923.3623536-4-dhowells@redhat.com>
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     dhowells@redhat.com, netdev@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
        David Ahern <dsahern@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        Jens Axboe <axboe@kernel.dk>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Tom Herbert <tom@herbertland.com>,
        Tom Herbert <tom@quantonium.net>
Subject: Re: [PATCH net-next 3/4] kcm: Support MSG_SPLICE_PAGES
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Content-ID: <574369.1685523113.1@warthog.procyon.org.uk>
Date:   Wed, 31 May 2023 09:51:53 +0100
Message-ID: <574370.1685523113@warthog.procyon.org.uk>
Precedence: bulk

Jakub Kicinski <kuba@kernel.org> wrote:

> On Wed, 24 May 2023 15:49:22 +0100 David Howells wrote:
> > +			err = skb_splice_from_iter(skb, &msg->msg_iter, copy,
> > +						   sk->sk_allocation);
> > +			if (err < 0) {
> > +				if (err == -EMSGSIZE)
> > +					goto wait_for_memory;
> > +				goto out_error;
> > +			}
> >  
> 
> should there be a:
> 
> 		copy = err;
> or:
> 		copy -= msg_data_left(msg);
> 
> or some such here? Can we safely assume that skb_splice_from_iter() will
> copy all or nothing? 

Yeah.  Good point.  I didn't add one because the normal operation code doesn't
do that - but I guess that's all-or-nothing.

David