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.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 464CBC7EE22 for ; Tue, 2 May 2023 20:07:10 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.528812.822425 (Exim 4.92) (envelope-from ) id 1ptwH1-0003h0-Mu; Tue, 02 May 2023 20:06:55 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 528812.822425; Tue, 02 May 2023 20:06:55 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ptwH1-0003gt-K4; Tue, 02 May 2023 20:06:55 +0000 Received: by outflank-mailman (input) for mailman id 528812; Tue, 02 May 2023 20:06:54 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ptwH0-0003gj-Er for xen-devel@lists.xenproject.org; Tue, 02 May 2023 20:06:54 +0000 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id e0bd3cb8-e924-11ed-b225-6b7b168915f2; Tue, 02 May 2023 22:06:52 +0200 (CEST) Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-228-EPMPoQX1NfuQ2XU-a2gp2Q-1; Tue, 02 May 2023 16:06:48 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5758A85A588; Tue, 2 May 2023 20:06:47 +0000 (UTC) Received: from localhost (unknown [10.39.192.230]) by smtp.corp.redhat.com (Postfix) with ESMTP id C37E1C15BAE; Tue, 2 May 2023 20:06:46 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: e0bd3cb8-e924-11ed-b225-6b7b168915f2 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1683058011; 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=LgDhtbpQWSSNsgeEph8esneZJVWEPWcWGLZOnDkeVKE=; b=Kdbe6o3RSShoyolv1BJEpZjDP6CP1+4m4XuVtcQZgsQ8LZnWJ0ZRruYghKu6UwyXZPiH6I qEb+XNd2k/EysxjXB5O8vTPgiIC9pDlAMRg4iKbCoMn30TV93xjZDaSZ0cHl1p6ydQ5qJg fz0cE2caF7n03Xrp0fzPYt9s6obYr9Y= X-MC-Unique: EPMPoQX1NfuQ2XU-a2gp2Q-1 Date: Tue, 2 May 2023 16:06:45 -0400 From: Stefan Hajnoczi To: Kevin Wolf Cc: qemu-devel@nongnu.org, Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Juan Quintela , Julia Suvorova , xen-devel@lists.xenproject.org, eesposit@redhat.com, Richard Henderson , Fam Zheng , "Michael S. Tsirkin" , Coiby Xu , David Woodhouse , Marcel Apfelbaum , Peter Lieven , Paul Durrant , "Richard W.M. Jones" , qemu-block@nongnu.org, Stefano Garzarella , Anthony Perard , Stefan Weil , Xie Yongji , Paolo Bonzini , Aarushi Mehta , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Eduardo Habkost , Stefano Stabellini , Hanna Reitz , Ronnie Sahlberg Subject: Re: [PATCH v4 07/20] block/export: stop using is_external in vhost-user-blk server Message-ID: <20230502200645.GE535070@fedora> References: <20230425172716.1033562-1-stefanha@redhat.com> <20230425172716.1033562-8-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="O5xAqfWJ9HxCWIfk" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 --O5xAqfWJ9HxCWIfk Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, May 02, 2023 at 06:04:24PM +0200, Kevin Wolf wrote: > Am 25.04.2023 um 19:27 hat Stefan Hajnoczi geschrieben: > > vhost-user activity must be suspended during bdrv_drained_begin/end(). > > This prevents new requests from interfering with whatever is happening > > in the drained section. > >=20 > > Previously this was done using aio_set_fd_handler()'s is_external > > argument. In a multi-queue block layer world the aio_disable_external() > > API cannot be used since multiple AioContext may be processing I/O, not > > just one. > >=20 > > Switch to BlockDevOps->drained_begin/end() callbacks. > >=20 > > Signed-off-by: Stefan Hajnoczi > > --- > > block/export/vhost-user-blk-server.c | 43 ++++++++++++++-------------- > > util/vhost-user-server.c | 10 +++---- > > 2 files changed, 26 insertions(+), 27 deletions(-) > >=20 > > diff --git a/block/export/vhost-user-blk-server.c b/block/export/vhost-= user-blk-server.c > > index 092b86aae4..d20f69cd74 100644 > > --- a/block/export/vhost-user-blk-server.c > > +++ b/block/export/vhost-user-blk-server.c > > @@ -208,22 +208,6 @@ static const VuDevIface vu_blk_iface =3D { > > .process_msg =3D vu_blk_process_msg, > > }; > > =20 > > -static void blk_aio_attached(AioContext *ctx, void *opaque) > > -{ > > - VuBlkExport *vexp =3D opaque; > > - > > - vexp->export.ctx =3D ctx; > > - vhost_user_server_attach_aio_context(&vexp->vu_server, ctx); > > -} > > - > > -static void blk_aio_detach(void *opaque) > > -{ > > - VuBlkExport *vexp =3D opaque; > > - > > - vhost_user_server_detach_aio_context(&vexp->vu_server); > > - vexp->export.ctx =3D NULL; > > -} >=20 > So for changing the AioContext, we now rely on the fact that the node to > be changed is always drained, so the drain callbacks implicitly cover > this case, too? Yes. > > static void > > vu_blk_initialize_config(BlockDriverState *bs, > > struct virtio_blk_config *config, > > @@ -272,6 +256,25 @@ static void vu_blk_exp_resize(void *opaque) > > vu_config_change_msg(&vexp->vu_server.vu_dev); > > } > > =20 > > +/* Called with vexp->export.ctx acquired */ > > +static void vu_blk_drained_begin(void *opaque) > > +{ > > + VuBlkExport *vexp =3D opaque; > > + > > + vhost_user_server_detach_aio_context(&vexp->vu_server); > > +} >=20 > Compared to the old code, we're losing the vexp->export.ctx =3D NULL. This > is correct at this point because after drained_begin we still keep > processing requests until we arrive at a quiescent state. >=20 > However, if we detach the AioContext because we're deleting the > iothread, won't we end up with a dangling pointer in vexp->export.ctx? > Or can we be certain that nothing interesting happens before drained_end > updates it with a new valid pointer again? If you want I can add the detach() callback back again and set ctx to NULL there? Stefan --O5xAqfWJ9HxCWIfk Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmRRbVUACgkQnKSrs4Gr c8i4OAf+KMBGicSKs6PxKeNThQpFSMAOYw12vnQg0N97hfarjPeaKf9lZmdJLKB7 McPjsLuRThNx0snklzDlcRovZKNZcV5EjEddXKA1ikDqZXDeLue4X717xIIV1RF0 oYAyyPcTXr9V1JKG2nKQzz1fK/zb0oXyEycRI1uPB1YjiL/NnBUZEdAG3DEZmBXK qjZcFpvChPe6DFydAfunLcRtoSASIb6cBLCeOFHXuTrKixFZeG9QDW87ONOMnG7D JF3Cjcfsn94R6SFWDOK2TGeKF7IY6kVJa+gOJXyTE2+n2vZhpezwmroM4kprRJGc TiMUeoBbZl3Oi5FrMOcj7MOeMEdRlw== =PCPd -----END PGP SIGNATURE----- --O5xAqfWJ9HxCWIfk--