From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=none (p=none dis=none) header.from=gibson.dropbear.id.au Authentication-Results: passt.top; dkim=pass (2048-bit key; secure) header.d=gibson.dropbear.id.au header.i=@gibson.dropbear.id.au header.a=rsa-sha256 header.s=202602 header.b=PZOHY9pc; dkim-atps=neutral Received: from mail.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) by passt.top (Postfix) with ESMTPS id 2D5335A0265 for ; Tue, 24 Mar 2026 03:41:26 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=202602; t=1774320083; bh=ylh/589RUnB8zGC7xkmeSKOVYJDMuY3xqMLv2sLbod4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PZOHY9pcH0If5suHPwQwpCieVJpRVD2lQBrhQCof7CBtDqjYzfzou9h4Pon56sp+5 8KhipFVl19t1UoLr4NAPjkknbisOfPxFrxwfKOwNo2kywRNDHpbZQkaZR0TVAQRHwV IBcs3wf/6fqudioCa4wIzQu/IL7PGYi3YQFj3R37ZW5INlDeDzLgXoapraus5JmqDo RwOwmQtVolpidcwwJBXugvqfYao7/d2eP+w9dmAC/2K5PD7y2hPoAFM8eFRgpjWb/x 3UwT3K7Op+gruxh+pM7eCjFNvJSeO4FGSXbGbWinDRWp5qelVfdDN3Bs7BPfpuDBhe SoZGXa6sgrVHg== Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4ffvS30phwz4wCm; Tue, 24 Mar 2026 13:41:23 +1100 (AEDT) Date: Tue, 24 Mar 2026 13:41:18 +1100 From: David Gibson To: Laurent Vivier Subject: Re: [PATCH v4 4/5] iov: Add IOV_PUT_HEADER() and with_header() to write header data back to iov_tail Message-ID: References: <20260323143151.538673-1-lvivier@redhat.com> <20260323143151.538673-5-lvivier@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="JSVvJx8cU4Mgw7/c" Content-Disposition: inline In-Reply-To: <20260323143151.538673-5-lvivier@redhat.com> Message-ID-Hash: EHIXQRNFQ5TJVGZ5N6SQYY36Y4N2B5AO X-Message-ID-Hash: EHIXQRNFQ5TJVGZ5N6SQYY36Y4N2B5AO X-MailFrom: dgibson@gandalf.ozlabs.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: --JSVvJx8cU4Mgw7/c Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Mar 23, 2026 at 03:31:50PM +0100, Laurent Vivier wrote: > Add iov_put_header_() and its wrapper macro IOV_PUT_HEADER() as a > counterpart to IOV_PEEK_HEADER(). This writes header data back to an > iov_tail after modification. If the header pointer matches the > original iov buffer location, the data was already modified in place > and no copy is needed. Otherwise, it copies the data back using > iov_from_buf(). >=20 > Add with_header(), a for-loop macro that combines IOV_PEEK_HEADER() > and IOV_PUT_HEADER() to allow modifying a header in place within a > block scope. >=20 > Signed-off-by: Laurent Vivier > --- > iov.c | 22 ++++++++++++++++++++++ > iov.h | 25 ++++++++++++++++++++++++- > 2 files changed, 46 insertions(+), 1 deletion(-) >=20 > diff --git a/iov.c b/iov.c > index 8134b8c9f988..7fc9c3c78a32 100644 > --- a/iov.c > +++ b/iov.c > @@ -308,6 +308,28 @@ void *iov_peek_header_(struct iov_tail *tail, void *= v, size_t len, size_t align) > return v; > } > =20 > +/** > + * iov_put_header_() - Write header back to an IOV tail > + * @tail: IOV tail to write header to > + * @v: Pointer to header data to write > + * @len: Length of header to write, in bytes > + * > + * Return: number of bytes written > + */ > +/* cppcheck-suppress unusedFunction */ > +size_t iov_put_header_(const struct iov_tail *tail, const void *v, size_= t len) > +{ > + size_t l =3D len; > + > + /* iov_peek_header_() already called iov_check_header() */ > + if ((char *)tail->iov[0].iov_base + tail->off !=3D v) > + l =3D iov_from_buf(tail->iov, tail->cnt, tail->off, v, len); > + > + assert(l =3D=3D len); > + > + return l; > +} > + > /** > * iov_remove_header_() - Remove a header from an IOV tail > * @tail: IOV tail to remove header from (modified) > diff --git a/iov.h b/iov.h > index d295d05b3bab..4ce425ccdbe5 100644 > --- a/iov.h > +++ b/iov.h > @@ -90,6 +90,7 @@ bool iov_tail_prune(struct iov_tail *tail); > size_t iov_tail_size(struct iov_tail *tail); > bool iov_drop_header(struct iov_tail *tail, size_t len); > void *iov_peek_header_(struct iov_tail *tail, void *v, size_t len, size_= t align); > +size_t iov_put_header_(const struct iov_tail *tail, const void *v, size_= t len); > void *iov_remove_header_(struct iov_tail *tail, void *v, size_t len, siz= e_t align); > ssize_t iov_tail_clone(struct iovec *dst_iov, size_t dst_iov_cnt, > struct iov_tail *tail); > @@ -112,6 +113,16 @@ ssize_t iov_tail_clone(struct iovec *dst_iov, size_t= dst_iov_cnt, > sizeof(var_), \ > __alignof__(var_)))) > =20 > +/** > + * IOV_PUT_HEADER() - Write header back to an IOV tail > + * @tail_: IOV tail to write header to > + * @var_: Pointer to a variable containing the header data to write > + * > + * Return: number of bytes written > + */ > +#define IOV_PUT_HEADER(tail_, var_) \ > + (iov_put_header_((tail_), (var_), sizeof(*var_))) > + > /** > * IOV_REMOVE_HEADER() - Remove and return typed header from an IOV tail > * @tail_: IOV tail to remove header from (modified) > @@ -130,7 +141,8 @@ ssize_t iov_tail_clone(struct iovec *dst_iov, size_t = dst_iov_cnt, > ((__typeof__(var_) *)(iov_remove_header_((tail_), &(var_), \ > sizeof(var_), __alignof__(var_)))) > =20 > -/** IOV_DROP_HEADER() - Remove a typed header from an IOV tail > +/** > + * IOV_DROP_HEADER() - Remove a typed header from an IOV tail > * @tail_: IOV tail to remove header from (modified) > * @type_: Data type of the header to remove > * > @@ -138,4 +150,15 @@ ssize_t iov_tail_clone(struct iovec *dst_iov, size_t= dst_iov_cnt, > */ > #define IOV_DROP_HEADER(tail_, type_) iov_drop_header((tail_), sizeof(t= ype_)) > =20 > +/** > + * with_header() - Execute a block on a given header > + * @type: Data type of the header to modify We already use __typeof__ in IOV_PEEK_HEADER(), so we should be able to use that to avoid explicitly passing the type. > + * @hdr_: Variable name to receive the header pointer > + * @tail_: IOV tail to peek/put the header from/to > + */ > +#define with_header(type_, hdr_, tail_) \ > + for (type_ store_, *hdr_ =3D IOV_PEEK_HEADER(tail_, store_); \ > + hdr_; \ > + IOV_PUT_HEADER(tail_, hdr_), hdr_ =3D NULL) > + > #endif /* IOVEC_H */ > --=20 > 2.53.0 >=20 --=20 David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson --JSVvJx8cU4Mgw7/c Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEO+dNsU4E3yXUXRK2zQJF27ox2GcFAmnB+c0ACgkQzQJF27ox 2Gdh6w/+OUrsF9ODaZEnd+diYTM0dkglB4bvJ921/RF42h081d/6BpHNQFuhjKwc fRmNJeNj7QeQy0ubCC1DhDOmfZL3wNkLGG/lWaBXO22nWtxP6uAAYQ88j0E/Npy3 XL9xVCjy+mr8ZrJnVZUdnMGr8yFokBjTnugWwO9r5NzkAOHSbVMH754xjc5mEjCi UaGZGB0QCVzDZDTkqP60J24PQSGqRbtJxDFi2Xp6GR7p9K20i5SL2USl4cZgS4Gp UovcZH7uCTwrat5aqMl2iNwUCZfpSGweo8467d1e5N048i7WFbuaUeZRqdDN3OBZ uvOJOaEu/qIe0PRKZAx1cAWIMQlk1hCOgoJF5/Q8ABEJgPcya6MPPyVYXCvCz2tw vRmBC1cqE8tMMY4P3OnDEsvyWWFJlcopUtlq+pUyk3X3V6Ze3gzF7afL8ddHwSJR 4/J3w4Ej/hcBm5GvqTD9kFZbJ/njcl7VI0Y3m5bazec1n87/kjm44wkewyBmFSjg B3Ez0D0IZoPdRQu91d7+hPKStqPv6VrKzw1H+j0+xS4s0bfItD1zhiCK4DHxALo6 KUIsqCxVv7Es64kaZIZgZTX3jASfNDG5ewqezBRq36ZLkvIziiAZxwwoR5O8vXGb MHAPZrzIyqSg+/bGV2vgsF6KlsZvyPlicLR8e9zydQjLvVcmv4E= =7IS8 -----END PGP SIGNATURE----- --JSVvJx8cU4Mgw7/c--