From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42101) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XOwW5-0001o7-1V for qemu-devel@nongnu.org; Tue, 02 Sep 2014 18:25:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XOwVy-0001k3-7n for qemu-devel@nongnu.org; Tue, 02 Sep 2014 18:25:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56000) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XOwVy-0001jr-18 for qemu-devel@nongnu.org; Tue, 02 Sep 2014 18:25:26 -0400 From: Max Reitz Date: Wed, 3 Sep 2014 00:25:08 +0200 Message-Id: <1409696709-27623-3-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 2/3] docs/qcow2: Correct refcount_block_entries 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 A refblock entry may have a different size than 16 bits, it may even be smaller than a byte. Correct the refcount_block_entries calculation accordingly. Signed-off-by: Max Reitz --- docs/specs/qcow2.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt index cfbc8b0..0a878aa 100644 --- a/docs/specs/qcow2.txt +++ b/docs/specs/qcow2.txt @@ -183,7 +183,7 @@ blocks and are exactly one cluster in size. Given a offset into the image file, the refcount of its cluster can be obtained as follows: - refcount_block_entries = (cluster_size / sizeof(uint16_t)) + refcount_block_entries = (cluster_size * 8 / refcount_bits) refcount_block_index = (offset / cluster_size) % refcount_block_entries refcount_table_index = (offset / cluster_size) / refcount_block_entries -- 2.1.0