From nobody Tue Feb 10 07:20:08 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1527614880163872.7443570399435; Tue, 29 May 2018 10:28:00 -0700 (PDT) Received: from localhost ([::1]:34118 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fNiPf-0000pz-7J for importer@patchew.org; Tue, 29 May 2018 13:27:59 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58365) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fNiKT-00055r-QQ for qemu-devel@nongnu.org; Tue, 29 May 2018 13:22:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fNiKR-0001rZ-9F for qemu-devel@nongnu.org; Tue, 29 May 2018 13:22:37 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:36786 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fNiKM-0001of-FM; Tue, 29 May 2018 13:22:30 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1C3CA4023112; Tue, 29 May 2018 17:22:30 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-116-193.ams2.redhat.com [10.36.116.193]) by smtp.corp.redhat.com (Postfix) with ESMTP id BCF27111762D; Tue, 29 May 2018 17:22:28 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Date: Tue, 29 May 2018 19:21:48 +0200 Message-Id: <20180529172156.29311-13-kwolf@redhat.com> In-Reply-To: <20180529172156.29311-1-kwolf@redhat.com> References: <20180529172156.29311-1-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Tue, 29 May 2018 17:22:30 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Tue, 29 May 2018 17:22:30 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'kwolf@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [PATCH v2 12/20] block: Don't poll in parent drain callbacks X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, famz@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com, stefanha@redhat.com, pbonzini@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" bdrv_do_drained_begin() is only safe if we have a single BDRV_POLL_WHILE() after quiescing all affected nodes. We cannot allow that parent callbacks introduce a nested polling loop that could cause graph changes while we're traversing the graph. Split off bdrv_do_drained_begin_quiesce(), which only quiesces a single node without waiting for its requests to complete. These requests will be waited for in the BDRV_POLL_WHILE() call down the call chain. Signed-off-by: Kevin Wolf --- include/block/block.h | 9 +++++++++ block.c | 2 +- block/io.c | 24 ++++++++++++++++-------- 3 files changed, 26 insertions(+), 9 deletions(-) diff --git a/include/block/block.h b/include/block/block.h index 56962e7ee7..6026c1385e 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -589,6 +589,15 @@ bool bdrv_drain_poll(BlockDriverState *bs, bool recurs= ive, void bdrv_drained_begin(BlockDriverState *bs); =20 /** + * bdrv_do_drained_begin_quiesce: + * + * Quiesces a BDS like bdrv_drained_begin(), but does not wait for already + * running requests to complete. + */ +void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, + BdrvChild *parent); + +/** * Like bdrv_drained_begin, but recursively begins a quiesced section for * exclusive access to all child nodes as well. */ diff --git a/block.c b/block.c index 8ca2cf27b4..1405d1180b 100644 --- a/block.c +++ b/block.c @@ -817,7 +817,7 @@ static char *bdrv_child_get_parent_desc(BdrvChild *c) static void bdrv_child_cb_drained_begin(BdrvChild *child) { BlockDriverState *bs =3D child->opaque; - bdrv_drained_begin(bs); + bdrv_do_drained_begin_quiesce(bs, NULL); } =20 static bool bdrv_child_cb_drained_poll(BdrvChild *child) diff --git a/block/io.c b/block/io.c index 01784d1115..af14227af8 100644 --- a/block/io.c +++ b/block/io.c @@ -286,15 +286,10 @@ static void coroutine_fn bdrv_co_yield_to_drain(Block= DriverState *bs, assert(data.done); } =20 -void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive, - BdrvChild *parent, bool poll) +void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, + BdrvChild *parent) { - BdrvChild *child, *next; - - if (qemu_in_coroutine()) { - bdrv_co_yield_to_drain(bs, true, recursive, parent, poll); - return; - } + assert(!qemu_in_coroutine()); =20 /* Stop things in parent-to-child order */ if (atomic_fetch_inc(&bs->quiesce_counter) =3D=3D 0) { @@ -303,6 +298,19 @@ void bdrv_do_drained_begin(BlockDriverState *bs, bool = recursive, =20 bdrv_parent_drained_begin(bs, parent); bdrv_drain_invoke(bs, true); +} + +static void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive, + BdrvChild *parent, bool poll) +{ + BdrvChild *child, *next; + + if (qemu_in_coroutine()) { + bdrv_co_yield_to_drain(bs, true, recursive, parent, poll); + return; + } + + bdrv_do_drained_begin_quiesce(bs, parent); =20 if (recursive) { bs->recursive_quiesce_counter++; --=20 2.13.6