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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells 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 Cc: dhowells@redhat.com, netdev@vger.kernel.org, "David S. Miller" , Eric Dumazet , Paolo Abeni , Willem de Bruijn , David Ahern , Matthew Wilcox , Jens Axboe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Tom Herbert , Tom Herbert Subject: Re: [PATCH net-next 3/4] kcm: Support MSG_SPLICE_PAGES MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" 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> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: D4F851C001F X-Stat-Signature: ps6mmqzgkr3u61ufoz1wc7oj166zts7z X-Rspam-User: X-HE-Tag: 1685523124-635390 X-HE-Meta: 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 jWwM/+WN MAzXR9UKCDg2ih9+SAiVaXVjP0vrdeCuzc1i43ofeluV9li0Ro5l3KWF7nnDL3a59/IZ/uNREAWJ2KnpGNb0TaPeEFF9YQ2w/YHxqQxafwhnYbZMBCb+3RUk/XzgycaOQKFkov9jqRTRcSpmcJZRdnrXupFEaLsKqyNOr4l1sqz+75rQFcRdbdtO1+taEEeaiXPyc3+WtzpfnvtlrVX6jFd2eBX6EeWhwwLBR2rx9+wYcZSY6IJZh1zTpDuQ3d52U50RkdrMNZqeVNOmcdwE3fRqxT0ok5gakak51IS7YKrGMX+VJFVS+JR9EFe+56Ft9OPV58HCRpASMsbY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Jakub Kicinski 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