From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([208.118.235.92]:52505)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <eblake@redhat.com>) id 1S7oGT-0006Ie-7Q
	for qemu-devel@nongnu.org; Wed, 14 Mar 2012 09:29:23 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <eblake@redhat.com>) id 1S7oG0-0005jH-Vk
	for qemu-devel@nongnu.org; Wed, 14 Mar 2012 09:29:16 -0400
Received: from mx1.redhat.com ([209.132.183.28]:22654)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <eblake@redhat.com>) id 1S7oG0-0005h6-NN
	for qemu-devel@nongnu.org; Wed, 14 Mar 2012 09:28:48 -0400
Message-ID: <4F609D0C.4000708@redhat.com>
Date: Wed, 14 Mar 2012 07:28:44 -0600
From: Eric Blake <eblake@redhat.com>
MIME-Version: 1.0
References: <CAJSP0QVeBfWnw+qtw7CiU=A4LE+kNTOMb0B-EWR=aVvqJLRNTQ@mail.gmail.com>
	<00c1eea5-ccb2-4b54-89f8-bdbf00fdc8a4@zmail17.collab.prod.int.phx2.redhat.com>
	<CAJSP0QWpGoaNn_q41sUbsZn8h24hMUHFQV2V6PMr8x6isVso_w@mail.gmail.com>
	<4F5F48F9.7090501@redhat.com>
	<CAJSP0QUJf6tcB2FEBEJg3hLTORmNtc7+v36n6QmppDWRxO1TVQ@mail.gmail.com>
	<4F606A09.2080906@redhat.com>
	<CAJSP0QVq-kpjAWc-gS9e7J7T7agPyUAY1adv4AxzhL4=uc6mwg@mail.gmail.com>
	<20120314101319.1a617a74@doriath.home>
	<20120314131932.GH27659@garlic.redhat.com>
In-Reply-To: <20120314131932.GH27659@garlic.redhat.com>
Content-Type: multipart/signed; micalg=pgp-sha256;
	protocol="application/pgp-signature";
	boundary="------------enig5D48B7FF793CFB5301D7A187"
Subject: Re: [Qemu-devel] [PATCH/RFC 0/7] Screendump to UNIX socket & in PNG
 format
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: Luiz Capitulino <lcapitulino@redhat.com>, Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, =?ISO-8859-1?Q?Marc-Andr=E9_Lureau?= <marcandre.lureau@redhat.com>, =?ISO-8859-1?Q?Marc-Andr=E9_Lureau?= <mlureau@redhat.com>, Gerd Hoffmann <kraxel@redhat.com>, =?ISO-8859-1?Q?Marc-Andr=E9_Lureau?= <marcandre.lureau@gmail.com>

This is an OpenPGP/MIME signed message (RFC 2440 and 3156)
--------------enig5D48B7FF793CFB5301D7A187
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

On 03/14/2012 07:19 AM, Alon Levy wrote:

>> Also, when returning the image via fd, we could offload its writing to=

>> a bh. This would give us a poor man's async support, where the biggest=

>> drawback would the lack of error detection (can this operation fail an=
yway?).
>>
>=20
> It leaves detection of completion up to the user, so inotify / parsing
> the file to see if it's complete (header says size X, but file is still=

> Y<X, not done..), which looks like as big a drawback.

Notification on a pipe is easy - the reader gets EOF when the writer
closes the fd, with no need to use inotify.  The only remaining issue is
whether the writer closes the fd early on error, so that the reader gets
an incomplete file.  But then the client can tell after getting EOF
whether the image file is complete (read the header, final file size is
too small), without having to have the intermediate management app
parsing headers during the streaming, although it would be a bonus if
there were a way to tell the management app that an error occurred and
qemu closed the write end early.

--=20
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


--------------enig5D48B7FF793CFB5301D7A187
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: OpenPGP digital signature
Content-Disposition: attachment; filename="signature.asc"

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.12 (GNU/Linux)
Comment: Public key at http://people.redhat.com/eblake/eblake.gpg
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iQEcBAEBCAAGBQJPYJ0NAAoJEKeha0olJ0NqrBcIAIgvYXIPPYOOVWF9Cyvk6sJI
J6I0tSEO8KUzJB32M38f3ylC+mSh6VbPNkdDevCrC8nZ5oNeQzc6vd2KyaIoIX55
Qiy32DJDT3q0dc2rmakxtAIFfxodQ9qaEnTRptvTOAMUg/FLi97FCyBqSeL3i00q
C18Dum7cDaBLIe5RDfKmnujQelwfUn/E1t8LhNd3DcSlCPdnTwZItTNgwfsy7WO1
YUT3wpYU8SKhGDpEOgYhTpcrPwd3J/1qzvJCyCBXDnbi3GWvEE4ZMBlZ2KXredre
oOp7Sxxh95U1BecHR/Qtc0ZPL9M1h859nPizkGmF3uz2IZuUEtrWpqi5ukp51Q4=
=qEQG
-----END PGP SIGNATURE-----

--------------enig5D48B7FF793CFB5301D7A187--