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 lists.gnu.org (lists.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 5680DEFD239 for ; Wed, 25 Feb 2026 10:04:33 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vvBka-0001hD-Rg; Wed, 25 Feb 2026 05:04:12 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vvBka-0001h4-3b for qemu-devel@nongnu.org; Wed, 25 Feb 2026 05:04:12 -0500 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 1vvBkY-0000z3-BC for qemu-devel@nongnu.org; Wed, 25 Feb 2026 05:04:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772013849; h=from:from:reply-to: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=6DghlwcnqP+nM+hN/ZTb6CF83dBnmYMc6ENouCr1nao=; b=QS9SrN/33N7z9gQbx27+G59Gk1aHmbzLmnqvXuViwTvWkMq/rzAfpDqqPRRIK2jexRtbS9 I7yxqiS6hvu44FApcLStnIFkiJByieWBcohezbnyUCqBcY4X1H9KfqA3IgB/xN+wQ2CpS+ vtouPzkztzcbWVFjX71Pc54gGLYU/Dg= 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-15-5AvJ-CqJMpuh9spits0Y-g-1; Wed, 25 Feb 2026 05:04:08 -0500 X-MC-Unique: 5AvJ-CqJMpuh9spits0Y-g-1 X-Mimecast-MFC-AGG-ID: 5AvJ-CqJMpuh9spits0Y-g_1772013847 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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 B76C8195609F; Wed, 25 Feb 2026 10:04:06 +0000 (UTC) Received: from redhat.com (unknown [10.45.225.165]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5E54B180066B; Wed, 25 Feb 2026 10:04:03 +0000 (UTC) Date: Wed, 25 Feb 2026 10:04:00 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Cc: Prasad Pandit , Ani Sinha , Peter Xu , Fabiano Rosas , kraxel@redhat.com, pbonzini@redhat.com, ani@anisinha.ca, Prasad Pandit , qemu-devel@nongnu.org Subject: Re: [PATCH v6 35/35] migration: return EEXIST when trying to add the same migration blocker Message-ID: References: <20260225035000.385950-1-anisinha@redhat.com> <20260225035000.385950-36-anisinha@redhat.com> <87342pw4l8.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87342pw4l8.fsf@pond.sub.org> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.358, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.659, 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Feb 25, 2026 at 10:32:51AM +0100, Markus Armbruster wrote: > Daniel P. Berrangé writes: > > > On Wed, Feb 25, 2026 at 11:35:15AM +0530, Prasad Pandit wrote: > >> On Wed, 25 Feb 2026 at 09:23, Ani Sinha wrote: > >> > Currently the code that adds a migration blocker does not check if the same > >> > blocker already exists. Return an EEXIST error code if there is an attempt to > >> > add the same migration blocker again. This way the same migration blocker will > >> > not get added twice. > >> > > >> > Suggested-by: Prasad Pandit > >> > Signed-off-by: Ani Sinha > >> > --- > >> > migration/migration.c | 4 ++++ > >> > 1 file changed, 4 insertions(+) > >> > > >> > diff --git a/migration/migration.c b/migration/migration.c > >> > index a5b0465ed3..1eb75fb7fb 100644 > >> > --- a/migration/migration.c > >> > +++ b/migration/migration.c > >> > @@ -1702,6 +1702,10 @@ static int add_blockers(Error **reasonp, unsigned modes, Error **errp) > > > > This method has an '**errp' parameter..... > > > >> > { > >> > for (MigMode mode = 0; mode < MIG_MODE__MAX; mode++) { > >> > if (modes & BIT(mode)) { > >> > + if (g_slist_index(migration_blockers[mode], > >> > + *reasonp) >= 0) { > >> > + return -EEXIST; > > > > .... so using -errno for return values is not appropriate - it must > > set 'errp' and return -1. > > Yes, it must set @errp on failure. Returning -1 would be wrong, > because: > > int migrate_add_blocker_modes(Error **reasonp, unsigned modes, Error **errp) > { > if (is_only_migratable(reasonp, modes, errp)) { > return -EACCES; > } else if (is_busy(reasonp, errp)) { > return -EBUSY; > } > return add_blockers(reasonp, modes, errp); > } > > If callers don't actually care for error codes, the entire nest of > functions could be simplified to return 0/-1 or true/false. AFAICT there is only 1 caller that cares spapr_mce_req_event tries to block migration while handling machine check exceptions, and if seeing EBUSY it will report a warning message. I'm not convinced it should be checking for EBUSY at all. If -only-migratable is set, it seems appropriate that it report the same warning message, as it is unable to block the migration. With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|