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 37DA8C4167D for ; Tue, 31 Oct 2023 19:05:19 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qxtxu-0003yw-GT; Tue, 31 Oct 2023 14:59:50 -0400 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 1qxtxt-0003y3-5m for qemu-devel@nongnu.org; Tue, 31 Oct 2023 14:59:49 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qxtxV-000662-Vv for qemu-devel@nongnu.org; Tue, 31 Oct 2023 14:59:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1698778765; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=F/zese4Un2SrXCtyjOdRUqT1WQNgqNx/q6FXGMvbhhE=; b=OfZeZ3+NgMwHIUvXQLYAm69rS8ONdzfDWU9T2VSl+g4D6HbkKnYFc5VJosM6C3Rbrp3sRI KXrJGyop+RjyuIFFgp/OCJCLjkhpDBicD5H9h40e6nzNT+0R2ZS12mOtK1/rYsw9SdaDbr kMWwjU8T7cYz9BD0lRN47crYY2hkBvw= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-654-jD6Rhd3EOq61qQMBJja5ug-1; Tue, 31 Oct 2023 14:59:21 -0400 X-MC-Unique: jD6Rhd3EOq61qQMBJja5ug-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6FD1A811E7D; Tue, 31 Oct 2023 18:59:21 +0000 (UTC) Received: from merkur.fritz.box (unknown [10.39.194.218]) by smtp.corp.redhat.com (Postfix) with ESMTP id D1E2C25C0; Tue, 31 Oct 2023 18:59:20 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [PULL 01/27] qemu-img: rebase: stop when reaching EOF of old backing file Date: Tue, 31 Oct 2023 19:58:52 +0100 Message-ID: <20231031185918.346940-2-kwolf@redhat.com> In-Reply-To: <20231031185918.346940-1-kwolf@redhat.com> References: <20231031185918.346940-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.481, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: 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 From: Andrey Drobyshev In case when we're rebasing within one backing chain, and when target image is larger than old backing file, bdrv_is_allocated_above() ends up setting *pnum = 0. As a result, target offset isn't getting incremented, and we get stuck in an infinite for loop. Let's detect this case and proceed further down the loop body, as the offsets beyond the old backing size need to be explicitly zeroed. Signed-off-by: Andrey Drobyshev Reviewed-by: Denis V. Lunev Reviewed-by: Hanna Czenczek Message-ID: <20230919165804.439110-2-andrey.drobyshev@virtuozzo.com> Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- qemu-img.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/qemu-img.c b/qemu-img.c index 585b65640f..2b2a3a86ca 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -3814,6 +3814,8 @@ static int img_rebase(int argc, char **argv) } if (prefix_chain_bs) { + uint64_t bytes = n; + /* * If cluster wasn't changed since prefix_chain, we don't need * to take action @@ -3826,9 +3828,18 @@ static int img_rebase(int argc, char **argv) strerror(-ret)); goto out; } - if (!ret) { + if (!ret && n) { continue; } + if (!n) { + /* + * If we've reached EOF of the old backing, it means that + * offsets beyond the old backing size were read as zeroes. + * Now we will need to explicitly zero the cluster in + * order to preserve that state after the rebase. + */ + n = bytes; + } } /* -- 2.41.0