From nobody Wed Dec 17 05:39:22 2025 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 (208.118.235.17 [208.118.235.17]) by mx.zohomail.com with SMTPS id 1529340800737962.6442863588128; Mon, 18 Jun 2018 09:53:20 -0700 (PDT) Received: from localhost ([::1]:35976 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fUxOy-0001sM-Vh for importer@patchew.org; Mon, 18 Jun 2018 12:53:13 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51866) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fUxHQ-0004sm-VE for qemu-devel@nongnu.org; Mon, 18 Jun 2018 12:45:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fUxHP-0006Hb-Mz for qemu-devel@nongnu.org; Mon, 18 Jun 2018 12:45:24 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:46496 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 1fUxHM-0006F4-E8; Mon, 18 Jun 2018 12:45:20 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 04A9F7DAC4; Mon, 18 Jun 2018 16:45:20 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-117-120.ams2.redhat.com [10.36.117.120]) by smtp.corp.redhat.com (Postfix) with ESMTP id 534522026D68; Mon, 18 Jun 2018 16:45:19 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Date: Mon, 18 Jun 2018 18:44:41 +0200 Message-Id: <20180618164504.24488-13-kwolf@redhat.com> In-Reply-To: <20180618164504.24488-1-kwolf@redhat.com> References: <20180618164504.24488-1-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Mon, 18 Jun 2018 16:45:20 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Mon, 18 Jun 2018 16:45:20 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.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] [PULL 12/35] 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, qemu-devel@nongnu.org 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 254ed2e4c9..067d24cc4a 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -591,6 +591,15 @@ 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 80abd3c2ae..50f8e3dc3b 100644 --- a/block.c +++ b/block.c @@ -818,7 +818,7 @@ 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 a413841bfc..ffb273708a 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