From patchwork Thu Nov 7 13:12:37 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 289349 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 9DB982C0098 for ; Fri, 8 Nov 2013 01:02:35 +1100 (EST) Received: from localhost ([::1]:40235 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VePSw-00020s-3a for incoming@patchwork.ozlabs.org; Thu, 07 Nov 2013 08:17:42 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51758) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VePQU-0007fL-L6 for qemu-devel@nongnu.org; Thu, 07 Nov 2013 08:15:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VePQO-0006sQ-MQ for qemu-devel@nongnu.org; Thu, 07 Nov 2013 08:15:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39216) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VePQO-0006qG-2K for qemu-devel@nongnu.org; Thu, 07 Nov 2013 08:15:04 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id rA7DE2q7027995 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 7 Nov 2013 08:14:02 -0500 Received: from localhost (ovpn-112-18.ams2.redhat.com [10.36.112.18]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id rA7DE1Qu028577; Thu, 7 Nov 2013 08:14:02 -0500 From: Stefan Hajnoczi To: Date: Thu, 7 Nov 2013 14:12:37 +0100 Message-Id: <1383829964-32364-30-git-send-email-stefanha@redhat.com> In-Reply-To: <1383829964-32364-1-git-send-email-stefanha@redhat.com> References: <1383829964-32364-1-git-send-email-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Jeff Cody , Stefan Hajnoczi , Anthony Liguori Subject: [Qemu-devel] [PULL 29/36] block: vhdx - remove BAT file offset bit shifting X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Jeff Cody Bit shifting can be fun, but in this case it was unnecessary. The upper 44 bits of the 64-bit BAT entry is specifies the File Offset, so we shifted the bits to get access to the value. However, per the spec the value is in MB. So we dutifully shifted back to the left by 20 bits, to convert to a true uint64_t file offset. This replaces those steps with just a bit mask, to get rid of the lower 20 bits instead. Signed-off-by: Jeff Cody Signed-off-by: Stefan Hajnoczi --- block/vhdx.c | 6 ++---- block/vhdx.h | 1 - 2 files changed, 2 insertions(+), 5 deletions(-) diff --git a/block/vhdx.c b/block/vhdx.c index 050f071..158edab 100644 --- a/block/vhdx.c +++ b/block/vhdx.c @@ -985,7 +985,7 @@ static void vhdx_block_translate(BDRVVHDXState *s, int64_t sector_num, sinfo->bytes_avail = sinfo->sectors_avail << s->logical_sector_size_bits; - sinfo->file_offset = s->bat[sinfo->bat_idx] >> VHDX_BAT_FILE_OFF_BITS; + sinfo->file_offset = s->bat[sinfo->bat_idx] & VHDX_BAT_FILE_OFF_MASK; sinfo->block_offset = block_offset << s->logical_sector_size_bits; @@ -999,7 +999,6 @@ static void vhdx_block_translate(BDRVVHDXState *s, int64_t sector_num, * in the block, and add in the payload data block offset * in the file, in bytes, to get the final read address */ - sinfo->file_offset <<= 20; /* now in bytes, rather than 1MB units */ sinfo->file_offset += sinfo->block_offset; } @@ -1098,8 +1097,7 @@ static void vhdx_update_bat_table_entry(BlockDriverState *bs, BDRVVHDXState *s, { /* The BAT entry is a uint64, with 44 bits for the file offset in units of * 1MB, and 3 bits for the block state. */ - s->bat[sinfo->bat_idx] = ((sinfo->file_offset>>20) << - VHDX_BAT_FILE_OFF_BITS); + s->bat[sinfo->bat_idx] = sinfo->file_offset; s->bat[sinfo->bat_idx] |= state & VHDX_BAT_STATE_BIT_MASK; diff --git a/block/vhdx.h b/block/vhdx.h index f331548..d3598e0 100644 --- a/block/vhdx.h +++ b/block/vhdx.h @@ -229,7 +229,6 @@ typedef struct QEMU_PACKED VHDXLogDataSector { /* upper 44 bits are the file offset in 1MB units lower 3 bits are the state other bits are reserved */ #define VHDX_BAT_STATE_BIT_MASK 0x07 -#define VHDX_BAT_FILE_OFF_BITS (64 - 44) #define VHDX_BAT_FILE_OFF_MASK 0xFFFFFFFFFFF00000 /* upper 44 bits */ typedef uint64_t VHDXBatEntry;