From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42113) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XOwW7-0001pD-3h for qemu-devel@nongnu.org; Tue, 02 Sep 2014 18:25:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XOwW0-0001kQ-GR for qemu-devel@nongnu.org; Tue, 02 Sep 2014 18:25:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42028) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XOwW0-0001kK-82 for qemu-devel@nongnu.org; Tue, 02 Sep 2014 18:25:28 -0400 From: Max Reitz Date: Wed, 3 Sep 2014 00:25:09 +0200 Message-Id: <1409696709-27623-4-git-send-email-mreitz@redhat.com> In-Reply-To: <1409696709-27623-1-git-send-email-mreitz@redhat.com> References: <1409696709-27623-1-git-send-email-mreitz@redhat.com> Subject: [Qemu-devel] [PATCH v2 3/3] docs/qcow2: Limit refcount_order to [0, 6] List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , =?UTF-8?q?Beno=C3=AEt=20Canet?= , Stefan Hajnoczi , Max Reitz Specify the upper limit of refcount_order to be 6 (that is, refcount_bits = 64). Any larger value does not make much sense when all offsets, sizes, cluster counts etc. "only" have a width of 64 bit as well, and very large values would be very difficult to support. Therefore, just cap it at the largest reasonable value. Suggested-by: Eric Blake Signed-off-by: Max Reitz --- docs/specs/qcow2.txt | 1 + 1 file changed, 1 insertion(+) diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt index 0a878aa..121dfc8 100644 --- a/docs/specs/qcow2.txt +++ b/docs/specs/qcow2.txt @@ -110,6 +110,7 @@ in the description of a field. in bits: refcount_bits = 1 << refcount_order). For version 2 images, the order is always assumed to be 4 (i.e. refcount_bits = 16). + This value may not exceed 6 (i.e. refcount_bits = 64). 100 - 103: header_length Length of the header structure in bytes. For version 2 -- 2.1.0