From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:50452)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@redhat.com>) id 1bcIzx-0005AY-Eq
	for qemu-devel@nongnu.org; Tue, 23 Aug 2016 17:12:42 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <stefanha@redhat.com>) id 1bcIzu-0007E0-70
	for qemu-devel@nongnu.org; Tue, 23 Aug 2016 17:12:41 -0400
Date: Tue, 23 Aug 2016 12:03:21 -0400
From: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20160823160321.GD3948@stefanha-x1.localdomain>
References: <20160822075517.5859-1-fullmanet@gmail.com>
	<20160822075517.5859-4-fullmanet@gmail.com>
	<20160822133526.GE28679@stefanha-x1.localdomain>
	<20160822140229.GB21105@vps308710.ovh.net>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha1;
	protocol="application/pgp-signature"; boundary="SFyWQ0h3ruR435lw"
Content-Disposition: inline
In-Reply-To: <20160822140229.GB21105@vps308710.ovh.net>
Subject: Re: [Qemu-devel] [PATCH 3/7] qemu-img: add more conv= conversions
 to dd
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel/>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Reda Sallahi <fullmanet@gmail.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, Kevin Wolf <kwolf@redhat.com>, Fam Zheng <famz@redhat.com>, qemu-block@nongnu.org, Max Reitz <mreitz@redhat.com>


--SFyWQ0h3ruR435lw
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Mon, Aug 22, 2016 at 04:02:30PM +0200, Reda Sallahi wrote:
> On Mon, Aug 22, 2016 at 09:35:26AM -0400, Stefan Hajnoczi wrote:
> > On Mon, Aug 22, 2016 at 09:55:13AM +0200, Reda Sallahi wrote:
> > > @@ -4325,20 +4388,43 @@ static int img_dd(int argc, char **argv)
> > > =20
> > >      for (out_pos =3D out.offset * obsz; in_pos < size; block_count++=
) {
> > >          int in_ret, out_ret;
> > > +        bsz =3D in.bsz;
> > > =20
> > >          if (in_pos + in.bsz > size) {
> > > -            in_ret =3D blk_pread(blk1, in_pos, in.buf, size - in_pos=
);
> > > -        } else {
> > > -            in_ret =3D blk_pread(blk1, in_pos, in.buf, in.bsz);
> > > +            bsz =3D size - in_pos;
> > > +        }
> > > +
> > > +        if (dd.conv & C_SYNC) {
> > > +            memset(in.buf, 0, in.bsz);
> > >          }
> >=20
> > Why is memset necessary?
>=20
> When we set conv=3Dnoerror,sync sync tells dd to pad each block with NULs=
 so
> that if there is an error it preserves the size of the input read.

Ah, I see.

Stefan

--SFyWQ0h3ruR435lw
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1

iQEcBAEBAgAGBQJXvHPJAAoJEJykq7OBq3PIMMUH/1GNSNWGx0HnA2dauwtc/jK/
nVL0eRqE6z0aNkiuX+wN/nABVpzW2WfaUkpkUDXMgHH4o0SgwrTp1E6Jnb1AKAJ4
ap2CygNcciwXsDnKA8iRclOm6+wn36/dp/q0o2VPPwZ9YGq2dlegET9FgXMrmiNs
2JGDJ5t9FYV+rkju3h4X17RAsVkkYMSXF/rHVWsBNvZcNe+QtVY4VQoaliWpSzV0
nFMtUL+H9QITnGBaE5V1sSToGEmzgAxBZtVYAw6RGX7sMSmYNXEVvYow6aHehXTp
PwWcPnuNdyjNfS6s0sD7YZclfpT5HTg+y7ijDV4iXAFURHKfPbvi9AxHKXLa/m4=
=hPBJ
-----END PGP SIGNATURE-----

--SFyWQ0h3ruR435lw--