From nobody Mon Feb 9 16:34:20 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=nongnu.org ARC-Seal: i=1; a=rsa-sha256; t=1685647798; cv=none; d=zohomail.com; s=zohoarc; b=SFPLDZQi3Sq5jKMNrCnvcHWP1ljQJwCb7tJfifd1pX3aZRNUNzB1g+cfiycm9UwpuAkIzZf0hjDp8FJvsyUJ8sDzXgAZiF5r1ahiWAAJUG2BHWQYs5HNKVJMrpFY16Ry9+28YO2Vb4igQhs36vAwguAnHl/DgmWrUIYPakgNFFw= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1685647798; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:Reply-To:References:Sender:Subject:To; bh=1+iZO2eqe7bJJVKqWLuAtOwCBi7Y53t/y79s+w6HweI=; b=JaLC4fKivCzjTKd8n5JHr0YOY6MqNJFw+lqNsxTXcQ8dQMLYF7uaI/QiyIxovIi/ibbp2cl10vkGpGM2NKy/j3guXAsRBqDT/8mmtaeZAmuKFWGlOMmzMvZKMxVU5xtbjJCOJGqoyXJKQa4VN3wx5atXF3nvS4Fg8HqOB34ixv4= ARC-Authentication-Results: i=1; mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1685647798623785.7924655890241; Thu, 1 Jun 2023 12:29:58 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q4nyn-0006oG-L0; Thu, 01 Jun 2023 15:29:01 -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 1q4nyZ-0006js-17; Thu, 01 Jun 2023 15:28:48 -0400 Received: from relay.virtuozzo.com ([130.117.225.111]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q4nyV-0005mC-S3; Thu, 01 Jun 2023 15:28:46 -0400 Received: from dev005.ch-qa.vzint.dev ([172.29.1.10]) by relay.virtuozzo.com with esmtp (Exim 4.96) (envelope-from ) id 1q4nyC-00DLDg-0X; Thu, 01 Jun 2023 21:28:36 +0200 To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, kwolf@redhat.com, hreitz@redhat.com, andrey.drobyshev@virtuozzo.com, den@virtuozzo.com Subject: [PATCH 1/6] qemu-img: rebase: stop when reaching EOF of old backing file Date: Thu, 1 Jun 2023 22:28:31 +0300 Message-Id: <20230601192836.598602-2-andrey.drobyshev@virtuozzo.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20230601192836.598602-1-andrey.drobyshev@virtuozzo.com> References: <20230601192836.598602-1-andrey.drobyshev@virtuozzo.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=130.117.225.111; envelope-from=andrey.drobyshev@virtuozzo.com; helo=relay.virtuozzo.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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: , Reply-to: Andrey Drobyshev From: Andrey Drobyshev via Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1685647799235100001 Content-Type: text/plain; charset="utf-8" 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 =3D 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 --- qemu-img.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/qemu-img.c b/qemu-img.c index 27f48051b0..78433f3746 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -3801,6 +3801,8 @@ static int img_rebase(int argc, char **argv) } =20 if (prefix_chain_bs) { + uint64_t bytes =3D n; + /* * If cluster wasn't changed since prefix_chain, we don't = need * to take action @@ -3813,9 +3815,18 @@ 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 t= hat + * offsets beyond the old backing size were read as ze= roes. + * Now we will need to explicitly zero the cluster in + * order to preserve that state after the rebase. + */ + n =3D bytes; + } } =20 /* --=20 2.31.1