From nobody Sun Feb 8 16:31:20 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A0B4C7EE23 for ; Tue, 30 May 2023 20:34:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233534AbjE3UeN (ORCPT ); Tue, 30 May 2023 16:34:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229893AbjE3UeJ (ORCPT ); Tue, 30 May 2023 16:34:09 -0400 Received: from wout5-smtp.messagingengine.com (wout5-smtp.messagingengine.com [64.147.123.21]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 50BDDE42; Tue, 30 May 2023 13:33:32 -0700 (PDT) Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailout.west.internal (Postfix) with ESMTP id 0D022320096E; Tue, 30 May 2023 16:32:20 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute4.internal (MEProxy); Tue, 30 May 2023 16:32:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= invisiblethingslab.com; h=cc:cc:content-transfer-encoding :content-type:date:date:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:sender:subject :subject:to:to; s=fm1; t=1685478740; x=1685565140; bh=gJtXKfjMb5 k3PryJlBFsKsS3ZINd0EksqBFZ4ekKEDw=; b=iSW8ttt26dngYvxurKxiOI2vd1 WHoQ92v7hwye8qiWm/sMzD3pqp5ya8c2OA22dKJKDKSCyzxijZP+Dp144KoNmvpt K8OI+kD4ismX23LXNvkYBIS8haogcvQd7EEZ19u32N/1GOR8sh6VaGOBsVQxw9Bq zrT17xw8paAPsuaett1MoyqWDe6uGCPznnCFymKvWzjN2rUubwy9Ob0uFq6jMg76 gqlN1m7Mc8Mkxu+yjAxvH0vX7/PlJqdVVec52wcaqJpFToYt9AxPY3yOgBt+RjEI aG4fzuzWpC22NKMBxr6O/RMjHdv28qKWfTHlwgkpaOz+BcWrwFwxRmGMeaMg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:date:date:feedback-id:feedback-id:from:from :in-reply-to:in-reply-to:message-id:mime-version:references :reply-to:sender:subject:subject:to:to:x-me-proxy:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm1; t=1685478740; x= 1685565140; bh=gJtXKfjMb5k3PryJlBFsKsS3ZINd0EksqBFZ4ekKEDw=; b=o QbHhAjdGI/824Nl01Pip/x1ESJBxXGnNCUCk4Arc6BskEm0MTh9UC6MZYaR2q79S k1Uqb9Vj1z9f6r5u3H1HVCqm/h4f+Vs2C2I55ZxnoCF18+ZrNegBzgUSduwuENN3 ZelAmC1BB6EziOQZ1m0S4cDcLpBIGrjkaMEsTbam0kd7jHN3XymXk0VF7iAEn4+L g585WZp+QBIJWRDnqGJWJT85ZYmZick+DsS7QTOGtDLjDvulDczBAEFMf2pxjFDZ z70/jIsQbBWGVBj2a0QhQ3776f+UlGOsyvyOBXKD9nxTQaFTHfPjpO3nn2UqnNoO C4Idzu7QZyx3OsqotLhew== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvhedrfeekjedgudeglecutefuodetggdotefrod ftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfgh necuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmd enucfjughrpefhvfevufffkffojghfggfgsedtkeertdertddtnecuhfhrohhmpeffvghm ihcuofgrrhhivgcuqfgsvghnohhurhcuoeguvghmihesihhnvhhishhisghlvghthhhinh hgshhlrggsrdgtohhmqeenucggtffrrghtthgvrhhnpeejffejgffgueegudevvdejkefg hefghffhffejteekleeufeffteffhfdtudehteenucevlhhushhtvghrufhiiigvpedtne curfgrrhgrmhepmhgrihhlfhhrohhmpeguvghmihesihhnvhhishhisghlvghthhhinhhg shhlrggsrdgtohhm X-ME-Proxy: Feedback-ID: iac594737:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 30 May 2023 16:32:19 -0400 (EDT) From: Demi Marie Obenour To: Jens Axboe , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= , Alasdair Kergon , Mike Snitzer , dm-devel@redhat.com Cc: Demi Marie Obenour , =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?= , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org Subject: [PATCH v2 16/16] xen-blkback: Inform userspace that device has been opened Date: Tue, 30 May 2023 16:31:16 -0400 Message-Id: <20230530203116.2008-17-demi@invisiblethingslab.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230530203116.2008-1-demi@invisiblethingslab.com> References: <20230530203116.2008-1-demi@invisiblethingslab.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Set "opened" to "0" before the hotplug script is called. Once the device node has been opened, set "opened" to "1". "opened" is used exclusively by userspace. It serves two purposes: 1. It tells userspace that the diskseq Xenstore entry is supported. 2. It tells userspace that it can wait for "opened" to be set to 1. Once "opened" is 1, blkback has a reference to the device, so userspace doesn't need to keep one. Together, these changes allow userspace to use block devices with delete-on-close behavior, such as loop devices with the autoclear flag set or device-mapper devices with the deferred-remove flag set. Signed-off-by: Demi Marie Obenour --- drivers/block/xen-blkback/xenbus.c | 35 ++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback= /xenbus.c index 9c3eb148fbd802c74e626c3d7bcd69dcb09bd921..519a78aa9073d1faa1dce5c1b36= e95ae58da534b 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -3,6 +3,20 @@ Copyright (C) 2005 Rusty Russell Copyright (C) 2005 XenSource Ltd =20 +In addition to the Xenstore nodes required by the Xen block device +specification, this implementation of blkback uses a new Xenstore +node: "opened". blkback sets "opened" to "0" before the hotplug script +is called. Once the device node has been opened, blkback sets "opened" +to "1". + +"opened" is read exclusively by userspace. It serves two purposes: + +1. It tells userspace that diskseq@major:minor syntax for "physical-device= " is + supported. + +2. It tells userspace that it can wait for "opened" to be set to 1 after w= riting + "physical-device". Once "opened" is 1, blkback has a reference to the + device, so userspace doesn't need to keep one. =20 */ =20 @@ -699,6 +713,14 @@ static int xen_blkbk_probe(struct xenbus_device *dev, if (err) pr_warn("%s write out 'max-ring-page-order' failed\n", __func__); =20 + /* + * This informs userspace that the "opened" node will be set to "1" when + * the device has been opened successfully. + */ + err =3D xenbus_write(XBT_NIL, dev->nodename, "opened", "0"); + if (err) + goto fail; + err =3D xenbus_switch_state(dev, XenbusStateInitWait); if (err) goto fail; @@ -826,6 +848,19 @@ static void backend_changed(struct xenbus_watch *watch, goto fail; } =20 + /* + * Tell userspace that the device has been opened and that blkback has a + * reference to it. Userspace can then close the device or mark it as + * delete-on-close, knowing that blkback will keep the device open as + * long as necessary. + */ + err =3D xenbus_write(XBT_NIL, dev->nodename, "opened", "1"); + if (err) { + xenbus_dev_fatal(dev, err, "%s: notifying userspace device has been open= ed", + dev->nodename); + goto free_vbd; + } + err =3D xenvbd_sysfs_addif(dev); if (err) { xenbus_dev_fatal(dev, err, "creating sysfs entries"); --=20 Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab