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[130.117.225.111]) by mx.google.com with ESMTPS id ffacd0b85a97d-482e29010a3si8653194f8f.400.2026.08.27.09.09.10 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Aug 2026 09:09:10 -0700 (PDT) Received-SPF: pass (google.com: domain of andrey.zhadchenko@virtuozzo.com designates 130.117.225.111 as permitted sender) client-ip=130.117.225.111; Authentication-Results: mx.google.com; dkim=pass header.i=@virtuozzo.com header.s=relay header.b=BHeLUTy4; spf=pass (google.com: domain of andrey.zhadchenko@virtuozzo.com designates 130.117.225.111 as permitted sender) smtp.mailfrom=andrey.zhadchenko@virtuozzo.com; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=virtuozzo.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=MIME-Version:Message-ID:Date:Subject:From: Content-Type; bh=mdbwc/z0IZ7k2wJl4IBOjUbFkz/l4glOfyAXG0DFBM4=; b=BHeLUTy4kvrK MEA8CgjrHAgcx5vBuESzmbmUFkRgODwbvhytiG6W3XC1ImCKJ13Y+7sIHDwvsfw/Q17HcPdKP4KHQ MrCLvtvbgOgdFJi8rWxyzvQXU6h2M14Be43fGEwln2RUwQD+RFI5cA3KtVFnc3j7zKifF2EPahDm/ M1qjeKUe4EarEb5/K6vYryWog8a4AmHfo2DKtLTmzHzISN9xRSOxsMYOasPJGFMve4HoVQ615rVie 4P94AeNgXA9EVlbM3V2Cce8ygqlWGKs7KF7POUzZjhZ92D5l7T/uWvTTAh6pLK8A+/w1ZLXmEqCH+ 3hGVggoSEhGLumIoD6q5ow==; Received: from [130.117.225.5] (helo=vz9-demens-1.aci.vzint.dev) by relay.virtuozzo.com with esmtp (Exim 4.96) (envelope-from ) id 1wzccs-00FHQJ-1X; Thu, 27 Aug 2026 18:09:08 +0200 From: Andrey Zhadchenko To: ptikhomirov@virtuozzo.com, vasileios.almpanis@virtuozzo.com Date: Thu, 27 Aug 2026 19:06:17 +0300 Message-ID: <20260827160619.303398-10-andrey.zhadchenko@virtuozzo.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20260827160619.303398-1-andrey.zhadchenko@virtuozzo.com> References: <20260827160619.303398-1-andrey.zhadchenko@virtuozzo.com> MIME-Version: 1.0 X-OZ-Fwd: true Cc: devel@openvz.org Subject: [Devel] [PATCH VZ10 v4 09/11] drivers/md/dm-qcow2: allow shared L1 entries during merge from RO image X-BeenThere: devel@openvz.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: OpenVZ development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: devel-bounces@openvz.org Errors-To: devel-bounces@openvz.org For RO images with internal snapshots L1 entries are shared. Write-mode metadata parsing stops at such entries to avoid modifying a shared L2 table, which made prepare_backward_merge() see the cluster as unallocated and skip it with "nothing to merge": the merged result would silently lose all data under shared L1 entries. Allow such scenario in parse_l1() and ease WARN in prepare_backward_merge(). https://virtuozzo.atlassian.net/browse/VSTOR-138288 Feature: dm-qcow2: block device over QCOW2 files driver Signed-off-by: Andrey Zhadchenko --- v3/v4: - reorder a patch and remove a guard against images with internal snapshots drivers/md/dm-qcow2-map.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm-qcow2-map.c b/drivers/md/dm-qcow2-map.c index 25a0ea63b0da4..b69f8ae106d1f 100644 --- a/drivers/md/dm-qcow2-map.c +++ b/drivers/md/dm-qcow2-map.c @@ -1726,6 +1726,14 @@ static bool qio_is_fully_alloced(struct qcow2 *qcow2, struct qio *qio, return !(subclus_mask & ~alloced_mask); } +static bool qio_may_modify_image(struct qcow2 *qcow2, struct qio *qio) +{ + if (qcow2_file_is_writable(qcow2)) + return true; + + return !fake_merge_qio(qio); +} + static loff_t parse_l1(struct qcow2 *qcow2, struct qcow2_map *map, struct qio **qio, bool write) @@ -1762,7 +1770,8 @@ static loff_t parse_l1(struct qcow2 *qcow2, struct qcow2_map *map, goto out; if (delay_if_dirty(qcow2, l1->md, l1->index_in_page, qio)) goto out; - if (write && map->clu_is_cow) + /* Don't refuse L1 parse for merge qios with readonly disks */ + if (write && map->clu_is_cow && qio_may_modify_image(qcow2, *qio)) goto out; /* Avoid to return pos */ ret = pos; @@ -2061,6 +2070,10 @@ static int parse_metadata(struct qcow2 *qcow2, struct qio **qio, qio_discard_unmaps_cluster(qcow2, *qio, map))) return 0; + /* Don't need refcount table if we don't modify the image */ + if (!qio_may_modify_image(qcow2, *qio)) + return 0; + /* Now refcounters table/block */ ret = qcow2_handle_r1r2_maps(qcow2, pos, qio, &map->r1, &map->r2, map->compressed); @@ -2732,7 +2745,8 @@ static int prepare_backward_merge(struct qcow2 *qcow2, struct qio **qio, int ret; if (!map->data_clu_alloced) { - WARN_ON_ONCE(map->clu_is_cow); /* Strange COW at L1 */ + /* Strange COW at L1, except the merge from RO image */ + WARN_ON_ONCE(map->clu_is_cow && qio_may_modify_image(qcow2, *qio)); if (fake_merge_qio(*qio)) { /* Nothing is to merge */ goto endio; -- 2.43.5 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel