Am 08.10.2010 17:48, schrieb Stefan Hajnoczi:
> This patch introduces the qed on-disk layout and implements image
> creation. Later patches add read/write and other functionality.
>
> Signed-off-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
> ---
> Makefile.objs | 1 +
> block/qed.c | 530
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> block/qed.h | 148 ++++++++++++++++
> 3 files changed, 679 insertions(+), 0 deletions(-)
> create mode 100644 block/qed.c
> create mode 100644 block/qed.h
>
> diff --git a/Makefile.objs b/Makefile.objs
> index 816194a..ff15795 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -14,6 +14,7 @@ block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
>
> block-nested-y += raw.o cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o
> vpc.o vvfat.o
> block-nested-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o
> +block-nested-y += qed.o
> block-nested-y += parallels.o nbd.o blkdebug.o sheepdog.o blkverify.o
> block-nested-$(CONFIG_WIN32) += raw-win32.o
> block-nested-$(CONFIG_POSIX) += raw-posix.o
> diff --git a/block/qed.c b/block/qed.c
> new file mode 100644
> index 0000000..ea03798
> --- /dev/null
> +++ b/block/qed.c
> @@ -0,0 +1,530 @@
> +/*
> + * QEMU Enhanced Disk Format
> + *
> + * Copyright IBM, Corp. 2010
> + *
> + * Authors:
> + * Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
> + * Anthony Liguori <aligu...@us.ibm.com>
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include "qed.h"
> +
> +static int bdrv_qed_probe(const uint8_t *buf, int buf_size,
> + const char *filename)
> +{
> + const QEDHeader *header = (const void *)buf;
Too lazy to type the real type name? ;-)
> +
> + if (buf_size < sizeof(*header)) {
> + return 0;
> + }
> + if (le32_to_cpu(header->magic) != QED_MAGIC) {
> + return 0;
> + }
> + return 100;
> +}
> +
> +static void qed_header_le_to_cpu(const QEDHeader *le, QEDHeader *cpu)
> +{
> + cpu->magic = le32_to_cpu(le->magic);
> + cpu->cluster_size = le32_to_cpu(le->cluster_size);
> + cpu->table_size = le32_to_cpu(le->table_size);
> + cpu->header_size = le32_to_cpu(le->header_size);
> + cpu->features = le64_to_cpu(le->features);
> + cpu->compat_features = le64_to_cpu(le->compat_features);
> + cpu->l1_table_offset = le64_to_cpu(le->l1_table_offset);
> + cpu->image_size = le64_to_cpu(le->image_size);
> + cpu->backing_filename_offset = le32_to_cpu(le->backing_filename_offset);
> + cpu->backing_filename_size = le32_to_cpu(le->backing_filename_size);
> + cpu->backing_fmt_offset = le32_to_cpu(le->backing_fmt_offset);
> + cpu->backing_fmt_size = le32_to_cpu(le->backing_fmt_size);
> +}
> +
> +static void qed_header_cpu_to_le(const QEDHeader *cpu, QEDHeader *le)
> +{
> + le->magic = cpu_to_le32(cpu->magic);
> + le->cluster_size = cpu_to_le32(cpu->cluster_size);
> + le->table_size = cpu_to_le32(cpu->table_size);
> + le->header_size = cpu_to_le32(cpu->header_size);
> + le->features = cpu_to_le64(cpu->features);
> + le->compat_features = cpu_to_le64(cpu->compat_features);
> + le->l1_table_offset = cpu_to_le64(cpu->l1_table_offset);
> + le->image_size = cpu_to_le64(cpu->image_size);
> + le->backing_filename_offset = cpu_to_le32(cpu->backing_filename_offset);
> + le->backing_filename_size = cpu_to_le32(cpu->backing_filename_size);
> + le->backing_fmt_offset = cpu_to_le32(cpu->backing_fmt_offset);
> + le->backing_fmt_size = cpu_to_le32(cpu->backing_fmt_size);
> +}
> +
/** Returns the maximum virtual disk size in bytes */
> +static uint64_t qed_max_image_size(uint32_t cluster_size, uint32_t
> table_size)
> +{
> + uint64_t table_entries;
> + uint64_t l2_size;
> +
> + table_entries = (table_size * cluster_size) / sizeof(uint64_t);
> + l2_size = table_entries * cluster_size;
> +
> + return l2_size * table_entries;
> +}
> +
> +static bool qed_is_cluster_size_valid(uint32_t cluster_size)
> +{
> + if (cluster_size < QED_MIN_CLUSTER_SIZE ||
> + cluster_size > QED_MAX_CLUSTER_SIZE) {
> + return false;
> + }
> + if (cluster_size & (cluster_size - 1)) {
> + return false; /* not power of 2 */
> + }
> + return true;
> +}
> +
> +static bool qed_is_table_size_valid(uint32_t table_size)
> +{
> + if (table_size < QED_MIN_TABLE_SIZE ||
> + table_size > QED_MAX_TABLE_SIZE) {
> + return false;
> + }
> + if (table_size & (table_size - 1)) {
> + return false; /* not power of 2 */
> + }
> + return true;
> +}
> +
> +static bool qed_is_image_size_valid(uint64_t image_size, uint32_t
> cluster_size,
> + uint32_t table_size)
> +{
> + if (image_size == 0) {
> + /* Supporting zero size images makes life harder because even the L1
> + * table is not needed. Make life simple and forbid zero size
> images.
> + */
> + return false;
> + }
Should the spec be updated to forbid zero size images?
> + if (image_size & (cluster_size - 1)) {
> + return false; /* not multiple of cluster size */
> + }
> + if (image_size > qed_max_image_size(cluster_size, table_size)) {
> + return false; /* image is too large */
> + }
> + return true;
> +}
> +
> +/**
> + * Read a string of known length from the image file
> + *
> + * @file: Image file
> + * @offset: File offset to start of string, in bytes
> + * @n: String length in bytes
> + * @buf: Destination buffer
> + * @buflen: Destination buffer length in bytes
> + *
> + * The string is NUL-terminated.
Return value?
> + */
> +static int qed_read_string(BlockDriverState *file, uint64_t offset, size_t n,
> + char *buf, size_t buflen)
> +{
> + int ret;
> + if (n >= buflen) {
> + return -EINVAL;
> + }
> + ret = bdrv_pread(file, offset, buf, n);
> + if (ret != n) {
> + return ret;
> + }
> + buf[n] = '\0';
> + return 0;
> +}
> +
> +static int bdrv_qed_open(BlockDriverState *bs, int flags)
> +{
> + BDRVQEDState *s = bs->opaque;
> + QEDHeader le_header;
> + int64_t file_size;
> + int ret;
> +
> + s->bs = bs;
> +
> + ret = bdrv_pread(bs->file, 0, &le_header, sizeof(le_header));
> + if (ret != sizeof(le_header)) {
> + return ret;
> + }
While this is correct because bdrv_pread never returns short reads, I
think "if (ret < 0)" would be easier to read.
> + qed_header_le_to_cpu(&le_header, &s->header);
> +
> + if (s->header.magic != QED_MAGIC) {
> + return -ENOENT;
> + }
> + if (s->header.features & ~QED_FEATURE_MASK) {
> + return -ENOTSUP; /* image uses unsupported feature bits */
> + }
> + if (!qed_is_cluster_size_valid(s->header.cluster_size)) {
> + return -EINVAL;
> + }
> +
> + /* Round up file size to the next cluster */
> + file_size = bdrv_getlength(bs->file);
> + if (file_size < 0) {
> + return file_size;
> + }
> + s->file_size = qed_start_of_cluster(s, file_size);
Aren't you rounding down despite the comment?
> +
> + if (!qed_is_table_size_valid(s->header.table_size)) {
> + return -EINVAL;
> + }
> + if (!qed_is_image_size_valid(s->header.image_size,
> + s->header.cluster_size,
> + s->header.table_size)) {
> + return -EINVAL;
> + }
> + if (!qed_check_table_offset(s, s->header.l1_table_offset)) {
> + return -EINVAL;
> + }
> +
> + s->table_nelems = (s->header.cluster_size * s->header.table_size) /
> + sizeof(uint64_t);
> + s->l2_shift = get_bits_from_size(s->header.cluster_size);
> + s->l2_mask = s->table_nelems - 1;
> + s->l1_shift = s->l2_shift + get_bits_from_size(s->l2_mask + 1);
> +
> + if ((s->header.features & QED_F_BACKING_FILE)) {
> + ret = qed_read_string(bs->file, s->header.backing_filename_offset,
> + s->header.backing_filename_size,
> bs->backing_file,
> + sizeof(bs->backing_file));
> + if (ret < 0) {
> + return ret;
> + }
> +
> + if ((s->header.compat_features & QED_CF_BACKING_FORMAT)) {
> + ret = qed_read_string(bs->file, s->header.backing_fmt_offset,
> + s->header.backing_fmt_size,
> + bs->backing_format,
> + sizeof(bs->backing_format));
> + if (ret < 0) {
> + return ret;
> + }
> + }
> + }
> + return ret;
I think this should be a return 0 instead of returning a random
non-negative number.
> +}
> +
> +static void bdrv_qed_close(BlockDriverState *bs)
> +{
> +}
> +
> +static void bdrv_qed_flush(BlockDriverState *bs)
> +{
> + bdrv_flush(bs->file);
> +}
> +
> +static int qed_create(const char *filename, uint32_t cluster_size,
> + uint64_t image_size, uint32_t table_size,
> + const char *backing_file, const char *backing_fmt)
> +{
> + QEDHeader header = {
> + .magic = QED_MAGIC,
> + .cluster_size = cluster_size,
> + .table_size = table_size,
> + .header_size = 1,
> + .features = 0,
> + .compat_features = 0,
> + .l1_table_offset = cluster_size,
> + .image_size = image_size,
> + };
> + QEDHeader le_header;
> + uint8_t *l1_table = NULL;
> + size_t l1_size = header.cluster_size * header.table_size;
> + int ret = 0;
> + int fd;
> +
> + fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0644);
Please use block.c functions (bdrv_create_file etc.) instead of POSIX
functions.
> + if (fd < 0) {
> + return -errno;
> + }
> +
> + if (backing_file) {
> + header.features |= QED_F_BACKING_FILE;
> + header.backing_filename_offset = sizeof(le_header);
> + header.backing_filename_size = strlen(backing_file);
> + if (backing_fmt) {
> + header.compat_features |= QED_CF_BACKING_FORMAT;
> + header.backing_fmt_offset = header.backing_filename_offset +
> + header.backing_filename_size;
> + header.backing_fmt_size = strlen(backing_fmt);
> + }
> + }
> +
> + qed_header_cpu_to_le(&header, &le_header);
> + if (qemu_write_full(fd, &le_header, sizeof(le_header)) !=
> sizeof(le_header)) {
> + ret = -errno;
> + goto out;
> + }
> + if (qemu_write_full(fd, backing_file, header.backing_filename_size) !=
> header.backing_filename_size) {
> + ret = -errno;
> + goto out;
> + }
> + if (qemu_write_full(fd, backing_fmt, header.backing_fmt_size) !=
> header.backing_fmt_size) {
> + ret = -errno;
> + goto out;
> + }
> +
> + l1_table = qemu_mallocz(l1_size);
> + lseek(fd, header.l1_table_offset, SEEK_SET);
> + if (qemu_write_full(fd, l1_table, l1_size) != l1_size) {
> + ret = -errno;
> + goto out;
> + }
> +
> +out:
> + qemu_free(l1_table);
> + close(fd);
> + return ret;
> +}
> +
> +static int bdrv_qed_create(const char *filename, QEMUOptionParameter
> *options)
> +{
> + uint64_t image_size = 0;
> + uint32_t cluster_size = QED_DEFAULT_CLUSTER_SIZE;
> + uint32_t table_size = QED_DEFAULT_TABLE_SIZE;
> + const char *backing_file = NULL;
> + const char *backing_fmt = NULL;
> +
> + while (options && options->name) {
> + if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
> + image_size = options->value.n;
> + } else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
> + backing_file = options->value.s;
> + } else if (!strcmp(options->name, BLOCK_OPT_BACKING_FMT)) {
> + backing_fmt = options->value.s;
> + } else if (!strcmp(options->name, BLOCK_OPT_CLUSTER_SIZE)) {
> + if (options->value.n) {
> + cluster_size = options->value.n;
> + }
> + } else if (!strcmp(options->name, "table_size")) {
> + if (options->value.n) {
> + table_size = options->value.n;
> + }
> + }
> + options++;
> + }
> +
> + if (!qed_is_cluster_size_valid(cluster_size)) {
> + fprintf(stderr, "QED cluster size must be within range [%u, %u] and
> power of 2\n",
> + QED_MIN_CLUSTER_SIZE, QED_MAX_CLUSTER_SIZE);
> + return -EINVAL;
> + }
> + if (!qed_is_table_size_valid(table_size)) {
> + fprintf(stderr, "QED table size must be within range [%u, %u] and
> power of 2\n",
> + QED_MIN_TABLE_SIZE, QED_MAX_TABLE_SIZE);
> + return -EINVAL;
> + }
> + if (!qed_is_image_size_valid(image_size, cluster_size, table_size)) {
> + char buffer[64];
> +
> + bytes_to_str(buffer, sizeof(buffer),
> + qed_max_image_size(cluster_size, table_size));
> +
> + fprintf(stderr,
> + "QED image size must be a non-zero multiple of cluster size
> and less than %s\n",
> + buffer);
> + return -EINVAL;
> + }
> +
> + return qed_create(filename, cluster_size, image_size, table_size,
> + backing_file, backing_fmt);
> +}
> +
> +static int bdrv_qed_is_allocated(BlockDriverState *bs, int64_t sector_num,
> + int nb_sectors, int *pnum)
> +{
> + return -ENOTSUP;
> +}
> +
> +static int bdrv_qed_make_empty(BlockDriverState *bs)
> +{
> + return -ENOTSUP;
> +}
> +
> +static BlockDriverAIOCB *bdrv_qed_aio_readv(BlockDriverState *bs,
> + int64_t sector_num,
> + QEMUIOVector *qiov, int
> nb_sectors,
> + BlockDriverCompletionFunc *cb,
> + void *opaque)
> +{
> + return NULL;
> +}
> +
> +static BlockDriverAIOCB *bdrv_qed_aio_writev(BlockDriverState *bs,
> + int64_t sector_num,
> + QEMUIOVector *qiov, int
> nb_sectors,
> + BlockDriverCompletionFunc *cb,
> + void *opaque)
> +{
> + return NULL;
> +}
> +
> +static BlockDriverAIOCB *bdrv_qed_aio_flush(BlockDriverState *bs,
> + BlockDriverCompletionFunc *cb,
> + void *opaque)
> +{
> + return bdrv_aio_flush(bs->file, cb, opaque);
> +}
> +
> +static int bdrv_qed_truncate(BlockDriverState *bs, int64_t offset)
> +{
> + return -ENOTSUP;
> +}
> +
> +static int64_t bdrv_qed_getlength(BlockDriverState *bs)
> +{
> + BDRVQEDState *s = bs->opaque;
> + return s->header.image_size;
> +}
> +
> +static int bdrv_qed_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
> +{
> + BDRVQEDState *s = bs->opaque;
> +
> + memset(bdi, 0, sizeof(*bdi));
> + bdi->cluster_size = s->header.cluster_size;
> + return 0;
> +}
> +
> +static int bdrv_qed_change_backing_file(BlockDriverState *bs,
> + const char *backing_file,
> + const char *backing_fmt)
> +{
> + BDRVQEDState *s = bs->opaque;
> + QEDHeader new_header, le_header;
> + void *buffer;
> + size_t buffer_len, backing_file_len, backing_fmt_len;
> + int ret;
> +
> + /* Refuse to set backing filename if unknown compat feature bits are
> + * active. If the image uses an unknown compat feature then we may not
> + * know the layout of data following the header structure and cannot
> safely
> + * add a new string.
> + */
> + if (backing_file && (s->header.compat_features &
> + ~QED_COMPAT_FEATURE_MASK)) {
> + return -ENOTSUP;
> + }
> +
> + memcpy(&new_header, &s->header, sizeof(new_header));
> +
> + new_header.features &= ~QED_F_BACKING_FILE;
> + new_header.compat_features &= ~QED_CF_BACKING_FORMAT;
> +
> + /* Adjust feature flags */
> + if (backing_file) {
> + new_header.features |= QED_F_BACKING_FILE;
> + if (backing_fmt) {
> + new_header.compat_features |= QED_CF_BACKING_FORMAT;
> + }
> + }
> +
> + /* Calculate new header size */
> + backing_file_len = backing_fmt_len = 0;
> +
> + if (backing_file) {
> + backing_file_len = strlen(backing_file);
> + if (backing_fmt) {
> + backing_fmt_len = strlen(backing_fmt);
> + }
> + }
> +
> + buffer_len = sizeof(new_header);
> + new_header.backing_filename_offset = buffer_len;
> + new_header.backing_filename_size = backing_file_len;
> + buffer_len += backing_file_len;
> + new_header.backing_fmt_offset = buffer_len;
> + new_header.backing_fmt_size = backing_fmt_len;
> + buffer_len += backing_fmt_len;
> +
> + /* Make sure we can rewrite header without failing */
> + if (buffer_len > new_header.header_size * new_header.cluster_size) {
> + return -ENOSPC;
> + }
> +
> + /* Prepare new header */
> + buffer = qemu_malloc(buffer_len);
> +
> + qed_header_cpu_to_le(&new_header, &le_header);
> + memcpy(buffer, &le_header, sizeof(le_header));
> + buffer_len = sizeof(le_header);
> +
> + memcpy(buffer + buffer_len, backing_file, backing_file_len);
> + buffer_len += backing_file_len;
> +
> + memcpy(buffer + buffer_len, backing_fmt, backing_fmt_len);
> + buffer_len += backing_fmt_len;
> +
> + /* Write new header */
> + ret = bdrv_pwrite_sync(bs->file, 0, buffer, buffer_len);
> + qemu_free(buffer);
> + if (ret == 0) {
> + memcpy(&s->header, &new_header, sizeof(new_header));
> + }
> + return ret;
> +}
> +
> +static int bdrv_qed_check(BlockDriverState *bs, BdrvCheckResult *result)
> +{
> + return -ENOTSUP;
> +}
> +
> +static QEMUOptionParameter qed_create_options[] = {
> + {
> + .name = BLOCK_OPT_SIZE,
> + .type = OPT_SIZE,
> + .help = "Virtual disk size (in bytes)"
> + }, {
> + .name = BLOCK_OPT_BACKING_FILE,
> + .type = OPT_STRING,
> + .help = "File name of a base image"
> + }, {
> + .name = BLOCK_OPT_BACKING_FMT,
> + .type = OPT_STRING,
> + .help = "Image format of the base image"
> + }, {
> + .name = BLOCK_OPT_CLUSTER_SIZE,
> + .type = OPT_SIZE,
> + .help = "Cluster size (in bytes)"
> + }, {
> + .name = "table_size",
What about introducing a constant for this?
> + .type = OPT_SIZE,
> + .help = "L1/L2 table size (in clusters)"
> + },
> + { /* end of list */ }
> +};
> +
> +static BlockDriver bdrv_qed = {
> + .format_name = "qed",
> + .instance_size = sizeof(BDRVQEDState),
> + .create_options = qed_create_options,
> +
> + .bdrv_probe = bdrv_qed_probe,
> + .bdrv_open = bdrv_qed_open,
> + .bdrv_close = bdrv_qed_close,
> + .bdrv_create = bdrv_qed_create,
> + .bdrv_flush = bdrv_qed_flush,
> + .bdrv_is_allocated = bdrv_qed_is_allocated,
> + .bdrv_make_empty = bdrv_qed_make_empty,
> + .bdrv_aio_readv = bdrv_qed_aio_readv,
> + .bdrv_aio_writev = bdrv_qed_aio_writev,
> + .bdrv_aio_flush = bdrv_qed_aio_flush,
> + .bdrv_truncate = bdrv_qed_truncate,
> + .bdrv_getlength = bdrv_qed_getlength,
> + .bdrv_get_info = bdrv_qed_get_info,
> + .bdrv_change_backing_file = bdrv_qed_change_backing_file,
> + .bdrv_check = bdrv_qed_check,
Please align the = of all definitions vertically.
> +};
> +
> +static void bdrv_qed_init(void)
> +{
> + bdrv_register(&bdrv_qed);
> +}
> +
> +block_init(bdrv_qed_init);
> diff --git a/block/qed.h b/block/qed.h
> new file mode 100644
> index 0000000..7ce95a7
> --- /dev/null
> +++ b/block/qed.h
> @@ -0,0 +1,148 @@
> +/*
> + * QEMU Enhanced Disk Format
> + *
> + * Copyright IBM, Corp. 2010
> + *
> + * Authors:
> + * Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
> + * Anthony Liguori <aligu...@us.ibm.com>
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#ifndef BLOCK_QED_H
> +#define BLOCK_QED_H
> +
> +#include "block_int.h"
> +
> +/* The layout of a QED file is as follows:
> + *
> + * +--------+----------+----------+----------+-----+
> + * | header | L1 table | cluster0 | cluster1 | ... |
> + * +--------+----------+----------+----------+-----+
> + *
> + * There is a 2-level pagetable for cluster allocation:
> + *
> + * +----------+
> + * | L1 table |
> + * +----------+
> + * ,------' | '------.
> + * +----------+ | +----------+
> + * | L2 table | ... | L2 table |
> + * +----------+ +----------+
> + * ,------' | '------.
> + * +----------+ | +----------+
> + * | Data | ... | Data |
> + * +----------+ +----------+
> + *
> + * The L1 table is fixed size and always present. L2 tables are allocated on
> + * demand. The L1 table size determines the maximum possible image size; it
> + * can be influenced using the cluster_size and table_size values.
> + *
> + * All fields are little-endian on disk.
> + */
> +
> +enum {
> + QED_MAGIC = 'Q' | 'E' << 8 | 'D' << 16 | '\0' << 24,
> +
> + /* The image supports a backing file */
> + QED_F_BACKING_FILE = 0x01,
> +
> + /* The image has the backing file format */
> + QED_CF_BACKING_FORMAT = 0x01,
> +
> + /* Feature bits must be used when the on-disk format changes */
> + QED_FEATURE_MASK = QED_F_BACKING_FILE, /* supported feature
> bits */
> + QED_COMPAT_FEATURE_MASK = QED_CF_BACKING_FORMAT, /* supported compat
> feature bits */
> +
> + /* Data is stored in groups of sectors called clusters. Cluster size
> must
> + * be large to avoid keeping too much metadata. I/O requests that have
> + * sub-cluster size will require read-modify-write.
> + */
> + QED_MIN_CLUSTER_SIZE = 4 * 1024, /* in bytes */
> + QED_MAX_CLUSTER_SIZE = 64 * 1024 * 1024,
> + QED_DEFAULT_CLUSTER_SIZE = 64 * 1024,
> +
> + /* Allocated clusters are tracked using a 2-level pagetable. Table size
> is
> + * a multiple of clusters so large maximum image sizes can be supported
> + * without jacking up the cluster size too much.
> + */
> + QED_MIN_TABLE_SIZE = 1, /* in clusters */
> + QED_MAX_TABLE_SIZE = 16,
> + QED_DEFAULT_TABLE_SIZE = 4,
> +};
> +
> +typedef struct {
> + uint32_t magic; /* QED\0 */
> +
> + uint32_t cluster_size; /* in bytes */
> + uint32_t table_size; /* for L1 and L2 tables, in clusters */
> + uint32_t header_size; /* in clusters */
> +
> + uint64_t features; /* format feature bits */
> + uint64_t compat_features; /* compatible feature bits */
> + uint64_t l1_table_offset; /* in bytes */
> + uint64_t image_size; /* total logical image size, in bytes */
> +
> + /* if (features & QED_F_BACKING_FILE) */
> + uint32_t backing_filename_offset; /* in bytes from start of header */
> + uint32_t backing_filename_size; /* in bytes */
> +
> + /* if (compat_features & QED_CF_BACKING_FORMAT) */
> + uint32_t backing_fmt_offset; /* in bytes from start of header */
> + uint32_t backing_fmt_size; /* in bytes */
> +} QEDHeader;
> +
> +typedef struct {
> + BlockDriverState *bs; /* device */
> + uint64_t file_size; /* length of image file, in bytes */
> +
> + QEDHeader header; /* always cpu-endian */
> + uint32_t table_nelems;
> + uint32_t l1_shift;
> + uint32_t l2_shift;
> + uint32_t l2_mask;
> +} BDRVQEDState;
> +
> +/**
> + * Utility functions
Sure that this is the right description for this function? ;-)
> + */
> +static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset)
> +{
> + return offset & ~(uint64_t)(s->header.cluster_size - 1);
> +}
> +
> +/**
> + * Test if a cluster offset is valid
> + */
> +static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset)
> +{
> + uint64_t header_size = (uint64_t)s->header.header_size *
> + s->header.cluster_size;
> +
> + if (offset & (s->header.cluster_size - 1)) {
> + return false;
> + }
> + return offset >= header_size && offset < s->file_size;
> +}
> +
> +/**
> + * Test if a table offset is valid
> + */
> +static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset)
> +{
> + uint64_t end_offset = offset + (s->header.table_size - 1) *
> + s->header.cluster_size;
> +
> + /* Overflow check */
> + if (end_offset <= offset) {
> + return false;
> + }
> +
> + return qed_check_cluster_offset(s, offset) &&
> + qed_check_cluster_offset(s, end_offset);
> +}
> +
> +#endif /* BLOCK_QED_H */
Kevin
