From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 329BAC02192 for ; Mon, 3 Feb 2025 19:20:12 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tf1yu-0004DL-Ff; Mon, 03 Feb 2025 14:19:40 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tf1yo-00046H-QA for qemu-devel@nongnu.org; Mon, 03 Feb 2025 14:19:36 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tf1ym-0008CB-7z for qemu-devel@nongnu.org; Mon, 03 Feb 2025 14:19:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1738610371; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=gRPOvXwBFqsddyoV1JdV/+3f7kPx7kXAOXxi+EjjvZg=; b=Z8Kgp3pS5xlt18/01sVcOFm34l2sZJZOq6axLVcjKDAdb8Jn4t9bBjoRKe3RX0VH5XrRZw yX/LPTv6AHqL8px1nvqzs9XzdX8oW/vqGHXrZqEIvXHDO9jYbJjFCsN1aXvoqzCG6BC4as bM5sN3YyfQGs3eYPkuAGg9Bo5WnCK1I= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-98-6sIrYJaKN3KpzWZxIifKwg-1; Mon, 03 Feb 2025 14:19:28 -0500 X-MC-Unique: 6sIrYJaKN3KpzWZxIifKwg-1 X-Mimecast-MFC-AGG-ID: 6sIrYJaKN3KpzWZxIifKwg Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D9FB9195604F; Mon, 3 Feb 2025 19:19:26 +0000 (UTC) Received: from localhost (unknown [10.2.16.131]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 6FE1B180035E; Mon, 3 Feb 2025 19:19:26 +0000 (UTC) Date: Mon, 3 Feb 2025 14:19:25 -0500 From: Stefan Hajnoczi To: Kevin Wolf Cc: qemu-block@nongnu.org, hreitz@redhat.com, pkrempa@redhat.com, peterx@redhat.com, farosas@suse.de, qemu-devel@nongnu.org Subject: Re: [PATCH v2 12/15] nbd/server: Support inactive nodes Message-ID: <20250203191925.GN268514@fedora> References: <20250130171240.286878-1-kwolf@redhat.com> <20250131095051.49708-3-kwolf@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="tmL3nVsalkbdz10b" Content-Disposition: inline In-Reply-To: <20250131095051.49708-3-kwolf@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --tmL3nVsalkbdz10b Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jan 31, 2025 at 10:50:48AM +0100, Kevin Wolf wrote: > In order to support running an NBD export on inactive nodes, we must > make sure to return errors for any operations that aren't allowed on > inactive nodes. Reads are the only operation we know we need for > inactive images, so to err on the side of caution, return errors for > everything else, even if some operations could possibly be okay. >=20 > Signed-off-by: Kevin Wolf > --- > nbd/server.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) >=20 > diff --git a/nbd/server.c b/nbd/server.c > index f64e47270c..2076fb2666 100644 > --- a/nbd/server.c > +++ b/nbd/server.c > @@ -2026,6 +2026,7 @@ static void nbd_export_delete(BlockExport *blk_exp) > const BlockExportDriver blk_exp_nbd =3D { > .type =3D BLOCK_EXPORT_TYPE_NBD, > .instance_size =3D sizeof(NBDExport), > + .supports_inactive =3D true, > .create =3D nbd_export_create, > .delete =3D nbd_export_delete, > .request_shutdown =3D nbd_export_request_shutdown, > @@ -2920,6 +2921,22 @@ static coroutine_fn int nbd_handle_request(NBDClie= nt *client, > NBDExport *exp =3D client->exp; > char *msg; > size_t i; > + bool inactive; > + > + WITH_GRAPH_RDLOCK_GUARD() { > + inactive =3D bdrv_is_inactive(blk_bs(exp->common.blk)); > + if (inactive) { > + switch (request->type) { > + case NBD_CMD_READ: > + /* These commands are allowed on inactive nodes */ > + break; > + default: > + /* Return an error for the rest */ > + return nbd_send_generic_reply(client, request, -EPERM, > + "export is inactive", errp= ); > + } > + } > + } Hmm...end of lock guard. What prevents the race where inactive changes before the request is performed? > =20 > switch (request->type) { > case NBD_CMD_CACHE: > --=20 > 2.48.1 >=20 --tmL3nVsalkbdz10b Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmehFrwACgkQnKSrs4Gr c8hOawgApX27dga9fIv37wxgvVLhDtRXN7ewR6gHcASd702AddIKncUTX2KsqGgM +Qbz/ZNkcmVX/DgBXAqUvz0nO5dpoOMeXIOZtUnuJgpGpLLU89R6v4VpoFkb1GbU HV8gLR8B79vaycEHU2JzWUwr1XXv3VqPDe0KV/UZ0vGdaEr+0cl8kM8la1CjedbY XgXR9osii4p7nvBUYOmBK7N630jg6QYXWo8c1jmKrBmx13qUoCaR91GcDSRIqO2K KxNl9Rtm6UoA1yXeqaT51kmWl43Ea+gXBFBR6Yc4U0N5nJ55gdbBJHqf4eggqT13 tiQfkVMh5LajZeT8M2JETB9x/iTc2A== =MRrg -----END PGP SIGNATURE----- --tmL3nVsalkbdz10b--