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[146.241.239.175]) by smtp.gmail.com with ESMTPSA id m7-20020a05620a13a700b00759342c9e77sm311947qki.16.2023.05.18.03.25.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 May 2023 03:25:17 -0700 (PDT) Message-ID: <47caea363e844bf716867c6a128d374cae4a5772.camel@redhat.com> Subject: Re: [PATCH net-next v7 03/16] net: Add a function to splice pages into an skbuff for MSG_SPLICE_PAGES From: Paolo Abeni To: David Howells Cc: netdev@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Willem de Bruijn , David Ahern , Matthew Wilcox , Al Viro , Christoph Hellwig , Jens Axboe , Jeff Layton , Christian Brauner , Chuck Lever III , Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Date: Thu, 18 May 2023 12:25:13 +0200 In-Reply-To: <1347187.1684403608@warthog.procyon.org.uk> References: <93aba6cc363e94a6efe433b3c77ec1b6b54f2919.camel@redhat.com> <20230515093345.396978-1-dhowells@redhat.com> <20230515093345.396978-4-dhowells@redhat.com> <1347187.1684403608@warthog.procyon.org.uk> User-Agent: Evolution 3.46.4 (3.46.4-1.fc37) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 77xbthq4wihwrdig88qj8o64grop7b7p X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 48CF52000D X-Rspam-User: X-HE-Tag: 1684405521-291148 X-HE-Meta: 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 FWfTe6hC 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 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: On Thu, 2023-05-18 at 10:53 +0100, David Howells wrote: > Paolo Abeni wrote: >=20 > > Minor nit: please respect the reverse x-mas tree order (there are a few > > other occurrences around) >=20 > I hadn't come across that. Normally I only apply that to the types so th= at > the names aren't all over the place. But whatever. >=20 > > > +=09=09if (space =3D=3D 0 && > > > +=09=09 !skb_can_coalesce(skb, skb_shinfo(skb)->nr_frags, > > > +=09=09=09=09 pages[0], off)) { > > > +=09=09=09iov_iter_revert(iter, len); > > > +=09=09=09break; > > > +=09=09} > >=20 > > It looks like the above condition/checks duplicate what the later > > skb_append_pagefrags() will perform below. I guess the above chunk > > could be removed? >=20 > Good point. There used to be an allocation between in the case sendpage_= ok() > failed and we wanted to copy the data. I've removed that for the moment. >=20 > > > +=09=09=09ret =3D -EIO; > > > +=09=09=09if (!sendpage_ok(page)) > > > +=09=09=09=09goto out; > >=20 > > My (limited) understanding is that the current sendpage code assumes > > that the caller provides/uses pages suitable for such use. The existing > > sendpage_ok() check is in place as way to try to catch possible code > > bug - via the WARN_ONCE(). > >=20 > > I think the same could be done here? >=20 > Yeah. >=20 > Okay, I made the attached changes to this patch. >=20 > David > --- > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 56d629ea2f3d..f4a5b51aed22 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -6923,10 +6923,10 @@ static void skb_splice_csum_page(struct sk_buff *= skb, struct page *page, > ssize_t skb_splice_from_iter(struct sk_buff *skb, struct iov_iter *iter, > =09=09=09 ssize_t maxsize, gfp_t gfp) > { > +=09size_t frag_limit =3D READ_ONCE(sysctl_max_skb_frags); > =09struct page *pages[8], **ppages =3D pages; > -=09unsigned int i; > =09ssize_t spliced =3D 0, ret =3D 0; > -=09size_t frag_limit =3D READ_ONCE(sysctl_max_skb_frags); > +=09unsigned int i; > =20 > =09while (iter->count > 0) { > =09=09ssize_t space, nr; > @@ -6946,20 +6946,13 @@ ssize_t skb_splice_from_iter(struct sk_buff *skb,= struct iov_iter *iter, > =09=09=09break; > =09=09} > =20 > -=09=09if (space =3D=3D 0 && > -=09=09 !skb_can_coalesce(skb, skb_shinfo(skb)->nr_frags, > -=09=09=09=09 pages[0], off)) { > -=09=09=09iov_iter_revert(iter, len); > -=09=09=09break; > -=09=09} > - > =09=09i =3D 0; > =09=09do { > =09=09=09struct page *page =3D pages[i++]; > =09=09=09size_t part =3D min_t(size_t, PAGE_SIZE - off, len); > =20 > =09=09=09ret =3D -EIO; > -=09=09=09if (!sendpage_ok(page)) > +=09=09=09if (WARN_ON_ONCE(!sendpage_ok(page))) FWIS the current TCP code also has a 'IS_ENABLED(CONFIG_DEBUG_VM) &&' guard, but I guess the plain WARN_ON_ONCE should be ok. Side node: we need the whole series alltogether, you need to repost even the unmodified patches. Thanks! Paolo