From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:51291) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gpGZM-0005mh-Va for qemu-devel@nongnu.org; Thu, 31 Jan 2019 12:56:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gpGZL-00056Q-DC for qemu-devel@nongnu.org; Thu, 31 Jan 2019 12:56:08 -0500 From: Kevin Wolf Date: Thu, 31 Jan 2019 18:55:42 +0100 Message-Id: <20190131175549.11691-5-kwolf@redhat.com> In-Reply-To: <20190131175549.11691-1-kwolf@redhat.com> References: <20190131175549.11691-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [RFC PATCH 04/11] qcow2: Prepare qcow2_get_cluster_type() for external data file List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, mreitz@redhat.com, eblake@redhat.com, qemu-devel@nongnu.org Signed-off-by: Kevin Wolf --- block/qcow2.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/block/qcow2.h b/block/qcow2.h index 2cb763bf11..b17bd502f5 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -519,7 +519,15 @@ static inline QCow2ClusterType qcow2_get_cluster_typ= e(BlockDriverState *bs, } return QCOW2_CLUSTER_ZERO_PLAIN; } else if (!(l2_entry & L2E_OFFSET_MASK)) { - return QCOW2_CLUSTER_UNALLOCATED; + /* Offset 0 generally means unallocated, but it is ambiguous wit= h + * external data files because 0 is a valid offset there. Howeve= r, all + * clusters in external data files always have refcount 1, so we= can + * rely on QCOW_OFLAG_COPIED to disambiguate. */ + if (has_data_file(bs) && (l2_entry & QCOW_OFLAG_COPIED)) { + return QCOW2_CLUSTER_NORMAL; + } else { + return QCOW2_CLUSTER_UNALLOCATED; + } } else { return QCOW2_CLUSTER_NORMAL; } --=20 2.20.1