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 lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (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 D6FE8C43458 for ; Wed, 1 Jul 2026 13:04:13 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1weubO-000427-K0; Wed, 01 Jul 2026 09:03:42 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1weubM-00041r-W6 for qemu-devel@nongnu.org; Wed, 01 Jul 2026 09:03:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1weubL-0002wt-AZ for qemu-devel@nongnu.org; Wed, 01 Jul 2026 09:03:40 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1782911018; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YUTdL2j7vm3/QhpLlr70daZucDuR76Seyns+8N6uVEc=; b=VAhA7io05y4haHgz1/oduaxP9pVG2ZGH/0DzltvUFyDLY5fnLqJJLgPNGoAQHF7Gi+tjgQ vuSt3MlYbf8FYUQkVoDxuOWxVHeGqoy+xD0HdfFbHc4s5OyRYBLtLVZYL1a2tAENIbkHOZ BCj/qb9ZyDYftrtKEY8H1j4BKPNPoxA= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-477-Wd4InJA_M-WhZplUhGVAKA-1; Wed, 01 Jul 2026 09:03:35 -0400 X-MC-Unique: Wd4InJA_M-WhZplUhGVAKA-1 X-Mimecast-MFC-AGG-ID: Wd4InJA_M-WhZplUhGVAKA_1782911014 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 33F711954234; Wed, 1 Jul 2026 13:03:34 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.44.22.4]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 088031955D53; Wed, 1 Jul 2026 13:03:33 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 9C1DF21E6920; Wed, 01 Jul 2026 15:03:30 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: Markus Armbruster , qemu-devel@nongnu.org, devel@lists.libvirt.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Paolo Bonzini , "Dr. David Alan Gilbert" , Alex =?utf-8?Q?Benn=C3=A9e?= , Christian Brauner , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Peter Krempa Subject: Re: [PATCH v5 01/35] qom: replace 'can_be_deleted' with 'prepare_delete' In-Reply-To: ("Daniel P. =?utf-8?Q?Berrang?= =?utf-8?Q?=C3=A9=22's?= message of "Tue, 30 Jun 2026 10:16:30 +0100") References: <20260624173752.2928717-1-berrange@redhat.com> <20260624173752.2928717-2-berrange@redhat.com> <87qzlopjlp.fsf@pond.sub.org> Date: Wed, 01 Jul 2026 15:03:30 +0200 Message-ID: <8733y26evx.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 8 X-Spam_score: 0.8 X-Spam_bar: / X-Spam_report: (0.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Daniel P. Berrang=C3=A9 writes: > On Tue, Jun 30, 2026 at 09:34:26AM +0200, Markus Armbruster wrote: >> Daniel P. Berrang=C3=A9 writes: >>=20 >> > While most objects can perform all their cleanup in the finalizer >> > method, there can be interactions with other resources / subsystems >> > / threads which require that some cleanup be performed on an user >> > creatable object before unparenting it and entering finalization. >> > >> > The current 'can_be_deleted' method runs in the deletion path and >> > is intended to be used to block deletion. While it could be used >> > to perform cleanup tasks, its name suggests it should be free of >> > side-effects. >> > >> > Generalize this by renaming it to 'prepare_delete', explicitly >> > allowing for cleanup to be provided. Existing users of 'can_be_deleted' >> > are re-written, which provides them with more detailed/tailored error >> > messages. >> > >> > Reviewed-by: Marc-Andr=C3=A9 Lureau >> > Tested-by: Peter Krempa >> > Signed-off-by: Daniel P. Berrang=C3=A9 >>=20 >> [...] >>=20 >> > diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c >> > index 7080f85f95..6faa0b2fd9 100644 >> > --- a/qom/object_interfaces.c >> > +++ b/qom/object_interfaces.c >> > @@ -32,16 +32,15 @@ bool user_creatable_complete(UserCreatable *uc, Er= ror **errp) >> > return !*errp; >> > } >> >=20=20 >> > -bool user_creatable_can_be_deleted(UserCreatable *uc) >> > +bool user_creatable_prepare_delete(UserCreatable *uc, Error **errp) >> > { >> > - >> > UserCreatableClass *ucc =3D USER_CREATABLE_GET_CLASS(uc); >> > + ERRP_GUARD(); >> >=20=20 >> > - if (ucc->can_be_deleted) { >> > - return ucc->can_be_deleted(uc); >> > - } else { >> > - return true; >> > + if (ucc->prepare_delete) { >> > + ucc->prepare_delete(uc, errp); >> > } >> > + return !*errp; >> > } >>=20 >> Simpler: >>=20 >> if (ucc->prepare_delete) { >> return ucc->prepare_delete(uc, errp); >> } >>=20 >> return true; > > ok > >>=20 >> >=20=20 >> > void user_creatable_add_qapi(ObjectOptions *options, Error **errp) >> > @@ -253,8 +252,7 @@ bool user_creatable_del(const char *id, Error **er= rp) >> > return false; >> > } >> >=20=20 >> > - if (!user_creatable_can_be_deleted(USER_CREATABLE(obj))) { >> > - error_setg(errp, "object '%s' is in use, can not be deleted",= id); >> > + if (!user_creatable_prepare_delete(USER_CREATABLE(obj), errp)) { >>=20 >> This changes error messages. >>=20 >> The old ones mention @id. >>=20 >> The new ones don't: >>=20 >> error_setg(errp, "Cryptodev backend is still in use"); >> error_setg(errp, "Host memory backend is still mapped"); >> error_setg(errp, "IOMMUFD backend still has %d users", be->users= ); >> error_setg(errp, "Throttle group still has multiple references"); >> error_setg(errp, "Deleting can bus devices is not supported"); Spel it CAN, please. >> error_setg(errp, "Deleting main loop is not supported"); >>=20 >> Visible in the diff to tests/qemu-iotests/245 below. >>=20 >> Because this runs within object-del, and @id is the argument provided by >> the user there, the error message is still sufficiently clear, I guess. >>=20 >> If this ever gets used where the object isn't obvious to the user from >> context, the error messages become sub-par. Observation, not a demand. >>=20 >> Please cover this change in the commit message. > > Oh yes, I remember being slightly annoyed at the need to do > this - I was surprised to realize that an Object does not > actually know its own 'id'. The 'id' only exists as the > name of the property in the parent. > > We could add an object_get_id() API which traveres obj->parent > and then iterates over child properties. Annoyingly O(n) time > for that, but perhaps not a big enough problem to worry about ? > At least for error reporting we're probably ok with that time > complexity even if there are 1000 objects registered as children. Could you use object_get_canonical_path_component()? [...]