From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:33596) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UWONq-0004BJ-HN for qemu-devel@nongnu.org; Sun, 28 Apr 2013 05:59:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UWONn-0006Xw-OU for qemu-devel@nongnu.org; Sun, 28 Apr 2013 05:59:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47940) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UWONn-0006XG-Ha for qemu-devel@nongnu.org; Sun, 28 Apr 2013 05:58:59 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r3S9wwIg015117 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Sun, 28 Apr 2013 05:58:58 -0400 Date: Sun, 28 Apr 2013 17:58:55 +0800 From: Fam Zheng Message-ID: <20130428095855.GA28366@localhost.localdomain> References: <56a0e0347fde5396fb6b2a260de5b1a867a588d6.1366726446.git.jcody@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56a0e0347fde5396fb6b2a260de5b1a867a588d6.1366726446.git.jcody@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2 3/5] block: initial VHDX driver support framework - supports open and probe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jeff Cody Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com On Tue, 04/23 10:24, Jeff Cody wrote: > +/* opens the specified header block from the VHDX file header section */ > +static int vhdx_parse_header(BlockDriverState *bs, BDRVVHDXState *s) > +{ > + int ret = 0; > + vhdx_header *header1; > + vhdx_header *header2; > + uint64_t h1_seq = 0; > + uint64_t h2_seq = 0; > + uint8_t *buffer; > + > + header1 = qemu_blockalign(bs, sizeof(vhdx_header)); > + header2 = qemu_blockalign(bs, sizeof(vhdx_header)); > + > + buffer = qemu_blockalign(bs, VHDX_HEADER_SIZE); > + > + s->headers[0] = header1; > + s->headers[1] = header2; > + Logic for header1 and header2 are completely the same, IMO it might be better to avoid code with a loop. > + /* We have to read the whole VHDX_HEADER_SIZE instead of > + * sizeof(vhdx_header), because the checksum is over the whole > + * region */ > + ret = bdrv_pread(bs->file, VHDX_HEADER1_OFFSET, buffer, VHDX_HEADER_SIZE); > + if (ret < 0) { > + goto fail; > + } > + /* copy over just the relevant portion that we need */ > + memcpy(header1, buffer, sizeof(vhdx_header)); > + vhdx_header_le_import(header1); > + > + if (vhdx_checksum_is_valid(buffer, VHDX_HEADER_SIZE, 4) && > + header1->signature == VHDX_HDR_MAGIC) { > + h1_seq = header1->sequence_number; > + } Do we need to check the version here? As the specification page 15 says: The Version field specifies the version of the VHDX format used within the VHDX file. This field must be set to 1. If it is not, a parser must not attempt to parse the file using the details from this format specification. > + > + ret = bdrv_pread(bs->file, VHDX_HEADER2_OFFSET, buffer, VHDX_HEADER_SIZE); > + if (ret < 0) { > + goto fail; > + } > + /* copy over just the relevant portion that we need */ > + memcpy(header2, buffer, sizeof(vhdx_header)); > + vhdx_header_le_import(header2); > + > + if (vhdx_checksum_is_valid(buffer, VHDX_HEADER_SIZE, 4) && > + header2->signature == VHDX_HDR_MAGIC) { > + h2_seq = header2->sequence_number; > + } Same as above. > + > + if (h1_seq > h2_seq) { > + s->curr_header = 0; > + } else if (h2_seq > h1_seq) { > + s->curr_header = 1; > + } else { > + printf("NO VALID HEADER\n"); > + ret = -EINVAL; > + goto fail; > + } > + > + ret = 0; > + > + goto exit; > + > +fail: > + qemu_vfree(header1); > + qemu_vfree(header2); > + s->headers[0] = NULL; > + s->headers[1] = NULL; > +exit: > + qemu_vfree(buffer); > + return ret; > +} -- Fam