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Fri, 29 Nov 2019 11:18:39 +0000 From: Vladimir Sementsov-Ogievskiy To: Max Reitz , "qemu-block@nongnu.org" Subject: Re: [PATCH for-5.0 v2 13/23] mirror: Double-check immediately before replacing Thread-Topic: [PATCH for-5.0 v2 13/23] mirror: Double-check immediately before replacing Thread-Index: AQHVmKmBOvSfRSt4Xky0bXKFn4jsKKeiHCqA Date: Fri, 29 Nov 2019 11:18:39 +0000 Message-ID: <247c6f17-a425-0bb6-1c9f-a01a01cc3b37@virtuozzo.com> References: <20191111160216.197086-1-mreitz@redhat.com> <20191111160216.197086-14-mreitz@redhat.com> In-Reply-To: <20191111160216.197086-14-mreitz@redhat.com> Accept-Language: ru-RU, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-clientproxiedby: HE1PR0402CA0003.eurprd04.prod.outlook.com (2603:10a6:3:d0::13) To AM6PR08MB4423.eurprd08.prod.outlook.com (2603:10a6:20b:bf::12) authentication-results: spf=none (sender IP is ) smtp.mailfrom=vsementsov@virtuozzo.com; x-ms-exchange-messagesentrepresentingtype: 1 x-tagtoolbar-keys: D20191129141837146 x-originating-ip: [185.231.240.5] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 626a6a8c-447a-45fd-7374-08d774bde27b x-ms-traffictypediagnostic: AM6PR08MB4550: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:3826; 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charset="Windows-1252" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: virtuozzo.com X-MS-Exchange-CrossTenant-Network-Message-Id: 626a6a8c-447a-45fd-7374-08d774bde27b X-MS-Exchange-CrossTenant-originalarrivaltime: 29 Nov 2019 11:18:39.5335 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 0bc7f26d-0264-416e-a6fc-8352af79c58f X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 0fNIx12o7Evwaf/gUr4cbqT7PRvWDGrNG+QknbBqLSFRNTPsWbgIxHOD8y3/klLZbSovyu3gwqK6mcNQGa/xgkxAef9dV6TWmBrcZ9sZgyc= X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6PR08MB4550 X-detected-operating-system: by eggs.gnu.org: Windows 7 or 8 [fuzzy] X-Received-From: 40.107.2.113 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Alberto Garcia , "qemu-devel@nongnu.org" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 11.11.2019 19:02, Max Reitz wrote: > There is no guarantee that we can still replace the node we want to > replace at the end of the mirror job. Double-check by calling > bdrv_recurse_can_replace(). >=20 > Signed-off-by: Max Reitz > --- > block/mirror.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) >=20 > diff --git a/block/mirror.c b/block/mirror.c > index f0f2d9dff1..68a4404666 100644 > --- a/block/mirror.c > +++ b/block/mirror.c > @@ -695,7 +695,19 @@ static int mirror_exit_common(Job *job) > * drain potential other users of the BDS before changing the g= raph. */ > assert(s->in_drain); > bdrv_drained_begin(target_bs); > - bdrv_replace_node(to_replace, target_bs, &local_err); > + /* > + * Cannot use check_to_replace_node() here, because that would > + * check for an op blocker on @to_replace, and we have our own > + * there. > + */ interesting, that check_to_replace_node would acquire aio context of src.. Here we acquire aio context only if s->to_replace set (above this hunk).. I= sn't it a bug? If it is, it's preexisting, and not directly related to the patch, so here: Reviewed-by: Vladimir Sementsov-Ogievskiy > + if (bdrv_recurse_can_replace(src, to_replace)) { > + bdrv_replace_node(to_replace, target_bs, &local_err); > + } else { > + error_setg(&local_err, "Can no longer replace '%s' by '%s', = " > + "because it can no longer be guaranteed that doin= g so " > + "would not lead to an abrupt change of visible da= ta", > + to_replace->node_name, target_bs->node_name); > + } > bdrv_drained_end(target_bs); > if (local_err) { > error_report_err(local_err); >=20 --=20 Best regards, Vladimir