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qed: Add QEMU Enhanced Disk image format

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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 <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2010-12-06 16:08:00 +00:00 committed by Kevin Wolf
parent 71af014f14
commit 75411d236d
4 changed files with 704 additions and 0 deletions
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1
Makefile.objs
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@ -20,6 +20,7 @@ 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

554
block/qed.c Normal file
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@ -0,0 +1,554 @@
/*
* QEMU Enhanced Disk Format
*
* Copyright IBM, Corp. 2010
*
* Authors:
* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2 or later.
* See the COPYING.LIB 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 QEDHeader *)buf;
if (buf_size < sizeof(*header)) {
return 0;
}
if (le32_to_cpu(header->magic) != QED_MAGIC) {
return 0;
}
return 100;
}
/**
* Check whether an image format is raw
*
* @fmt: Backing file format, may be NULL
*/
static bool qed_fmt_is_raw(const char *fmt)
{
return fmt && strcmp(fmt, "raw") == 0;
}
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->autoclear_features = le64_to_cpu(le->autoclear_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);
}
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->autoclear_features = cpu_to_le64(cpu->autoclear_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);
}
static int qed_write_header_sync(BDRVQEDState *s)
{
QEDHeader le;
int ret;
qed_header_cpu_to_le(&s->header, &le);
ret = bdrv_pwrite(s->bs->file, 0, &le, sizeof(le));
if (ret != sizeof(le)) {
return ret;
}
return 0;
}
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 % BDRV_SECTOR_SIZE != 0) {
return false; /* not multiple of sector 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
* @ret: 0 on success, -errno on failure
*
* The string is NUL-terminated.
*/
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 < 0) {
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 < 0) {
return ret;
}
ret = 0; /* ret should always be 0 or -errno */
qed_header_le_to_cpu(&le_header, &s->header);
if (s->header.magic != QED_MAGIC) {
return -EINVAL;
}
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 down file size to the last cluster */
file_size = bdrv_getlength(bs->file);
if (file_size < 0) {
return file_size;
}
s->file_size = qed_start_of_cluster(s, file_size);
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 = ffs(s->header.cluster_size) - 1;
s->l2_mask = s->table_nelems - 1;
s->l1_shift = s->l2_shift + ffs(s->table_nelems) - 1;
if ((s->header.features & QED_F_BACKING_FILE)) {
if ((uint64_t)s->header.backing_filename_offset +
s->header.backing_filename_size >
s->header.cluster_size * s->header.header_size) {
return -EINVAL;
}
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.features & QED_F_BACKING_FORMAT_NO_PROBE) {
pstrcpy(bs->backing_format, sizeof(bs->backing_format), "raw");
}
}
/* Reset unknown autoclear feature bits. This is a backwards
* compatibility mechanism that allows images to be opened by older
* programs, which "knock out" unknown feature bits. When an image is
* opened by a newer program again it can detect that the autoclear
* feature is no longer valid.
*/
if ((s->header.autoclear_features & ~QED_AUTOCLEAR_FEATURE_MASK) != 0 &&
!bdrv_is_read_only(bs->file)) {
s->header.autoclear_features &= QED_AUTOCLEAR_FEATURE_MASK;
ret = qed_write_header_sync(s);
if (ret) {
return ret;
}
/* From here on only known autoclear feature bits are valid */
bdrv_flush(bs->file);
}
return ret;
}
static void bdrv_qed_close(BlockDriverState *bs)
{
}
static int bdrv_qed_flush(BlockDriverState *bs)
{
return 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;
BlockDriverState *bs = NULL;
ret = bdrv_create_file(filename, NULL);
if (ret < 0) {
return ret;
}
ret = bdrv_file_open(&bs, filename, BDRV_O_RDWR | BDRV_O_CACHE_WB);
if (ret < 0) {
return ret;
}
if (backing_file) {
header.features |= QED_F_BACKING_FILE;
header.backing_filename_offset = sizeof(le_header);
header.backing_filename_size = strlen(backing_file);
if (qed_fmt_is_raw(backing_fmt)) {
header.features |= QED_F_BACKING_FORMAT_NO_PROBE;
}
}
qed_header_cpu_to_le(&header, &le_header);
ret = bdrv_pwrite(bs, 0, &le_header, sizeof(le_header));
if (ret < 0) {
goto out;
}
ret = bdrv_pwrite(bs, sizeof(le_header), backing_file,
header.backing_filename_size);
if (ret < 0) {
goto out;
}
l1_table = qemu_mallocz(l1_size);
ret = bdrv_pwrite(bs, header.l1_table_offset, l1_table, l1_size);
if (ret < 0) {
goto out;
}
ret = 0; /* success */
out:
qemu_free(l1_table);
bdrv_delete(bs);
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, BLOCK_OPT_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)) {
fprintf(stderr, "QED image size must be a non-zero multiple of "
"cluster size and less than %" PRIu64 " bytes\n",
qed_max_image_size(cluster_size, table_size));
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;
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 |
QED_F_BACKING_FORMAT_NO_PROBE);
/* Adjust feature flags */
if (backing_file) {
new_header.features |= QED_F_BACKING_FILE;
if (qed_fmt_is_raw(backing_fmt)) {
new_header.features |= QED_F_BACKING_FORMAT_NO_PROBE;
}
}
/* Calculate new header size */
backing_file_len = 0;
if (backing_file) {
backing_file_len = strlen(backing_file);
}
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;
/* 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;
/* 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 = BLOCK_OPT_TABLE_SIZE,
.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,
};
static void bdrv_qed_init(void)
{
bdrv_register(&bdrv_qed);
}
block_init(bdrv_qed_init);

148
block/qed.h Normal file
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@ -0,0 +1,148 @@
/*
* QEMU Enhanced Disk Format
*
* Copyright IBM, Corp. 2010
*
* Authors:
* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2 or later.
* See the COPYING.LIB 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 backing file format must not be probed, treat as raw image */
QED_F_BACKING_FORMAT_NO_PROBE = 0x04,
/* Feature bits must be used when the on-disk format changes */
QED_FEATURE_MASK = QED_F_BACKING_FILE | /* supported feature bits */
QED_F_BACKING_FORMAT_NO_PROBE,
QED_COMPAT_FEATURE_MASK = 0, /* supported compat feature bits */
QED_AUTOCLEAR_FEATURE_MASK = 0, /* supported autoclear 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 autoclear_features; /* self-resetting 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 */
} 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;
/**
* Round down to the start of a cluster
*/
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 */

1
block_int.h
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@ -37,6 +37,7 @@
#define BLOCK_OPT_BACKING_FILE "backing_file"
#define BLOCK_OPT_BACKING_FMT "backing_fmt"
#define BLOCK_OPT_CLUSTER_SIZE "cluster_size"
#define BLOCK_OPT_TABLE_SIZE "table_size"
#define BLOCK_OPT_PREALLOC "preallocation"
typedef struct AIOPool {