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qemu/block/qcow2.c
Kevin Wolf 5ea929e3d1 qcow2: Add bdrv_discard support 
This adds a bdrv_discard function to qcow2 that frees the discarded clusters.
It does not yet pass the discard on to the underlying file system driver, but
the space can be reused by future writes to the image.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2011-01-31 10:03:00 +01:00

1385 lines
40 KiB
C
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/*
* Block driver for the QCOW version 2 format
*
* Copyright (c) 2004-2006 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu-common.h"
#include "block_int.h"
#include "module.h"
#include <zlib.h>
#include "aes.h"
#include "block/qcow2.h"
#include "qemu-error.h"
/*
Differences with QCOW:
- Support for multiple incremental snapshots.
- Memory management by reference counts.
- Clusters which have a reference count of one have the bit
QCOW_OFLAG_COPIED to optimize write performance.
- Size of compressed clusters is stored in sectors to reduce bit usage
in the cluster offsets.
- Support for storing additional data (such as the VM state) in the
snapshots.
- If a backing store is used, the cluster size is not constrained
(could be backported to QCOW).
- L2 tables have always a size of one cluster.
*/
typedef struct {
uint32_t magic;
uint32_t len;
} QCowExtension;
#define QCOW2_EXT_MAGIC_END 0
#define QCOW2_EXT_MAGIC_BACKING_FORMAT 0xE2792ACA
static int qcow2_probe(const uint8_t *buf, int buf_size, const char *filename)
{
const QCowHeader *cow_header = (const void *)buf;
if (buf_size >= sizeof(QCowHeader) &&
be32_to_cpu(cow_header->magic) == QCOW_MAGIC &&
be32_to_cpu(cow_header->version) == QCOW_VERSION)
return 100;
else
return 0;
}
/*
* read qcow2 extension and fill bs
* start reading from start_offset
* finish reading upon magic of value 0 or when end_offset reached
* unknown magic is skipped (future extension this version knows nothing about)
* return 0 upon success, non-0 otherwise
*/
static int qcow2_read_extensions(BlockDriverState *bs, uint64_t start_offset,
uint64_t end_offset)
{
QCowExtension ext;
uint64_t offset;
#ifdef DEBUG_EXT
printf("qcow2_read_extensions: start=%ld end=%ld\n", start_offset, end_offset);
#endif
offset = start_offset;
while (offset < end_offset) {
#ifdef DEBUG_EXT
/* Sanity check */
if (offset > s->cluster_size)
printf("qcow2_read_extension: suspicious offset %lu\n", offset);
printf("attemting to read extended header in offset %lu\n", offset);
#endif
if (bdrv_pread(bs->file, offset, &ext, sizeof(ext)) != sizeof(ext)) {
fprintf(stderr, "qcow2_read_extension: ERROR: "
"pread fail from offset %" PRIu64 "\n",
offset);
return 1;
}
be32_to_cpus(&ext.magic);
be32_to_cpus(&ext.len);
offset += sizeof(ext);
#ifdef DEBUG_EXT
printf("ext.magic = 0x%x\n", ext.magic);
#endif
switch (ext.magic) {
case QCOW2_EXT_MAGIC_END:
return 0;
case QCOW2_EXT_MAGIC_BACKING_FORMAT:
if (ext.len >= sizeof(bs->backing_format)) {
fprintf(stderr, "ERROR: ext_backing_format: len=%u too large"
" (>=%zu)\n",
ext.len, sizeof(bs->backing_format));
return 2;
}
if (bdrv_pread(bs->file, offset , bs->backing_format,
ext.len) != ext.len)
return 3;
bs->backing_format[ext.len] = '\0';
#ifdef DEBUG_EXT
printf("Qcow2: Got format extension %s\n", bs->backing_format);
#endif
offset = ((offset + ext.len + 7) & ~7);
break;
default:
/* unknown magic -- just skip it */
offset = ((offset + ext.len + 7) & ~7);
break;
}
}
return 0;
}
static int qcow2_open(BlockDriverState *bs, int flags)
{
BDRVQcowState *s = bs->opaque;
int len, i, ret = 0;
QCowHeader header;
uint64_t ext_end;
bool writethrough;
ret = bdrv_pread(bs->file, 0, &header, sizeof(header));
if (ret < 0) {
goto fail;
}
be32_to_cpus(&header.magic);
be32_to_cpus(&header.version);
be64_to_cpus(&header.backing_file_offset);
be32_to_cpus(&header.backing_file_size);
be64_to_cpus(&header.size);
be32_to_cpus(&header.cluster_bits);
be32_to_cpus(&header.crypt_method);
be64_to_cpus(&header.l1_table_offset);
be32_to_cpus(&header.l1_size);
be64_to_cpus(&header.refcount_table_offset);
be32_to_cpus(&header.refcount_table_clusters);
be64_to_cpus(&header.snapshots_offset);
be32_to_cpus(&header.nb_snapshots);
if (header.magic != QCOW_MAGIC || header.version != QCOW_VERSION) {
ret = -EINVAL;
goto fail;
}
if (header.cluster_bits < MIN_CLUSTER_BITS ||
header.cluster_bits > MAX_CLUSTER_BITS) {
ret = -EINVAL;
goto fail;
}
if (header.crypt_method > QCOW_CRYPT_AES) {
ret = -EINVAL;
goto fail;
}
s->crypt_method_header = header.crypt_method;
if (s->crypt_method_header) {
bs->encrypted = 1;
}
s->cluster_bits = header.cluster_bits;
s->cluster_size = 1 << s->cluster_bits;
s->cluster_sectors = 1 << (s->cluster_bits - 9);
s->l2_bits = s->cluster_bits - 3; /* L2 is always one cluster */
s->l2_size = 1 << s->l2_bits;
bs->total_sectors = header.size / 512;
s->csize_shift = (62 - (s->cluster_bits - 8));
s->csize_mask = (1 << (s->cluster_bits - 8)) - 1;
s->cluster_offset_mask = (1LL << s->csize_shift) - 1;
s->refcount_table_offset = header.refcount_table_offset;
s->refcount_table_size =
header.refcount_table_clusters << (s->cluster_bits - 3);
s->snapshots_offset = header.snapshots_offset;
s->nb_snapshots = header.nb_snapshots;
/* read the level 1 table */
s->l1_size = header.l1_size;
s->l1_vm_state_index = size_to_l1(s, header.size);
/* the L1 table must contain at least enough entries to put
header.size bytes */
if (s->l1_size < s->l1_vm_state_index) {
ret = -EINVAL;
goto fail;
}
s->l1_table_offset = header.l1_table_offset;
if (s->l1_size > 0) {
s->l1_table = qemu_mallocz(
align_offset(s->l1_size * sizeof(uint64_t), 512));
ret = bdrv_pread(bs->file, s->l1_table_offset, s->l1_table,
s->l1_size * sizeof(uint64_t));
if (ret < 0) {
goto fail;
}
for(i = 0;i < s->l1_size; i++) {
be64_to_cpus(&s->l1_table[i]);
}
}
/* alloc L2 table/refcount block cache */
writethrough = ((flags & BDRV_O_CACHE_MASK) == 0);
s->l2_table_cache = qcow2_cache_create(bs, L2_CACHE_SIZE, writethrough);
s->refcount_block_cache = qcow2_cache_create(bs, REFCOUNT_CACHE_SIZE,
writethrough);
s->cluster_cache = qemu_malloc(s->cluster_size);
/* one more sector for decompressed data alignment */
s->cluster_data = qemu_malloc(QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size
+ 512);
s->cluster_cache_offset = -1;
ret = qcow2_refcount_init(bs);
if (ret != 0) {
goto fail;
}
QLIST_INIT(&s->cluster_allocs);
/* read qcow2 extensions */
if (header.backing_file_offset) {
ext_end = header.backing_file_offset;
} else {
ext_end = s->cluster_size;
}
if (qcow2_read_extensions(bs, sizeof(header), ext_end)) {
ret = -EINVAL;
goto fail;
}
/* read the backing file name */
if (header.backing_file_offset != 0) {
len = header.backing_file_size;
if (len > 1023) {
len = 1023;
}
ret = bdrv_pread(bs->file, header.backing_file_offset,
bs->backing_file, len);
if (ret < 0) {
goto fail;
}
bs->backing_file[len] = '\0';
}
if (qcow2_read_snapshots(bs) < 0) {
ret = -EINVAL;
goto fail;
}
#ifdef DEBUG_ALLOC
qcow2_check_refcounts(bs);
#endif
return ret;
fail:
qcow2_free_snapshots(bs);
qcow2_refcount_close(bs);
qemu_free(s->l1_table);
if (s->l2_table_cache) {
qcow2_cache_destroy(bs, s->l2_table_cache);
}
qemu_free(s->cluster_cache);
qemu_free(s->cluster_data);
return ret;
}
static int qcow2_set_key(BlockDriverState *bs, const char *key)
{
BDRVQcowState *s = bs->opaque;
uint8_t keybuf[16];
int len, i;
memset(keybuf, 0, 16);
len = strlen(key);
if (len > 16)
len = 16;
/* XXX: we could compress the chars to 7 bits to increase
entropy */
for(i = 0;i < len;i++) {
keybuf[i] = key[i];
}
s->crypt_method = s->crypt_method_header;
if (AES_set_encrypt_key(keybuf, 128, &s->aes_encrypt_key) != 0)
return -1;
if (AES_set_decrypt_key(keybuf, 128, &s->aes_decrypt_key) != 0)
return -1;
#if 0
/* test */
{
uint8_t in[16];
uint8_t out[16];
uint8_t tmp[16];
for(i=0;i<16;i++)
in[i] = i;
AES_encrypt(in, tmp, &s->aes_encrypt_key);
AES_decrypt(tmp, out, &s->aes_decrypt_key);
for(i = 0; i < 16; i++)
printf(" %02x", tmp[i]);
printf("\n");
for(i = 0; i < 16; i++)
printf(" %02x", out[i]);
printf("\n");
}
#endif
return 0;
}
static int qcow2_is_allocated(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, int *pnum)
{
uint64_t cluster_offset;
int ret;
*pnum = nb_sectors;
/* FIXME We can get errors here, but the bdrv_is_allocated interface can't
* pass them on today */
ret = qcow2_get_cluster_offset(bs, sector_num << 9, pnum, &cluster_offset);
if (ret < 0) {
*pnum = 0;
}
return (cluster_offset != 0);
}
/* handle reading after the end of the backing file */
int qcow2_backing_read1(BlockDriverState *bs, QEMUIOVector *qiov,
int64_t sector_num, int nb_sectors)
{
int n1;
if ((sector_num + nb_sectors) <= bs->total_sectors)
return nb_sectors;
if (sector_num >= bs->total_sectors)
n1 = 0;
else
n1 = bs->total_sectors - sector_num;
qemu_iovec_memset(qiov, 0, 512 * (nb_sectors - n1));
return n1;
}
typedef struct QCowAIOCB {
BlockDriverAIOCB common;
int64_t sector_num;
QEMUIOVector *qiov;
int remaining_sectors;
int cur_nr_sectors; /* number of sectors in current iteration */
uint64_t bytes_done;
uint64_t cluster_offset;
uint8_t *cluster_data;
BlockDriverAIOCB *hd_aiocb;
QEMUIOVector hd_qiov;
QEMUBH *bh;
QCowL2Meta l2meta;
QLIST_ENTRY(QCowAIOCB) next_depend;
} QCowAIOCB;
static void qcow2_aio_cancel(BlockDriverAIOCB *blockacb)
{
QCowAIOCB *acb = container_of(blockacb, QCowAIOCB, common);
if (acb->hd_aiocb)
bdrv_aio_cancel(acb->hd_aiocb);
qemu_aio_release(acb);
}
static AIOPool qcow2_aio_pool = {
.aiocb_size = sizeof(QCowAIOCB),
.cancel = qcow2_aio_cancel,
};
static void qcow2_aio_read_cb(void *opaque, int ret);
static void qcow2_aio_read_bh(void *opaque)
{
QCowAIOCB *acb = opaque;
qemu_bh_delete(acb->bh);
acb->bh = NULL;
qcow2_aio_read_cb(opaque, 0);
}
static int qcow2_schedule_bh(QEMUBHFunc *cb, QCowAIOCB *acb)
{
if (acb->bh)
return -EIO;
acb->bh = qemu_bh_new(cb, acb);
if (!acb->bh)
return -EIO;
qemu_bh_schedule(acb->bh);
return 0;
}
static void qcow2_aio_read_cb(void *opaque, int ret)
{
QCowAIOCB *acb = opaque;
BlockDriverState *bs = acb->common.bs;
BDRVQcowState *s = bs->opaque;
int index_in_cluster, n1;
acb->hd_aiocb = NULL;
if (ret < 0)
goto done;
/* post process the read buffer */
if (!acb->cluster_offset) {
/* nothing to do */
} else if (acb->cluster_offset & QCOW_OFLAG_COMPRESSED) {
/* nothing to do */
} else {
if (s->crypt_method) {
qcow2_encrypt_sectors(s, acb->sector_num, acb->cluster_data,
acb->cluster_data, acb->cur_nr_sectors, 0, &s->aes_decrypt_key);
qemu_iovec_reset(&acb->hd_qiov);
qemu_iovec_copy(&acb->hd_qiov, acb->qiov, acb->bytes_done,
acb->cur_nr_sectors * 512);
qemu_iovec_from_buffer(&acb->hd_qiov, acb->cluster_data,
512 * acb->cur_nr_sectors);
}
}
acb->remaining_sectors -= acb->cur_nr_sectors;
acb->sector_num += acb->cur_nr_sectors;
acb->bytes_done += acb->cur_nr_sectors * 512;
if (acb->remaining_sectors == 0) {
/* request completed */
ret = 0;
goto done;
}
/* prepare next AIO request */
acb->cur_nr_sectors = acb->remaining_sectors;
if (s->crypt_method) {
acb->cur_nr_sectors = MIN(acb->cur_nr_sectors,
QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors);
}
ret = qcow2_get_cluster_offset(bs, acb->sector_num << 9,
&acb->cur_nr_sectors, &acb->cluster_offset);
if (ret < 0) {
goto done;
}
index_in_cluster = acb->sector_num & (s->cluster_sectors - 1);
qemu_iovec_reset(&acb->hd_qiov);
qemu_iovec_copy(&acb->hd_qiov, acb->qiov, acb->bytes_done,
acb->cur_nr_sectors * 512);
if (!acb->cluster_offset) {
if (bs->backing_hd) {
/* read from the base image */
n1 = qcow2_backing_read1(bs->backing_hd, &acb->hd_qiov,
acb->sector_num, acb->cur_nr_sectors);
if (n1 > 0) {
BLKDBG_EVENT(bs->file, BLKDBG_READ_BACKING_AIO);
acb->hd_aiocb = bdrv_aio_readv(bs->backing_hd, acb->sector_num,
&acb->hd_qiov, acb->cur_nr_sectors,
qcow2_aio_read_cb, acb);
if (acb->hd_aiocb == NULL)
goto done;
} else {
ret = qcow2_schedule_bh(qcow2_aio_read_bh, acb);
if (ret < 0)
goto done;
}
} else {
/* Note: in this case, no need to wait */
qemu_iovec_memset(&acb->hd_qiov, 0, 512 * acb->cur_nr_sectors);
ret = qcow2_schedule_bh(qcow2_aio_read_bh, acb);
if (ret < 0)
goto done;
}
} else if (acb->cluster_offset & QCOW_OFLAG_COMPRESSED) {
/* add AIO support for compressed blocks ? */
if (qcow2_decompress_cluster(bs, acb->cluster_offset) < 0)
goto done;
qemu_iovec_from_buffer(&acb->hd_qiov,
s->cluster_cache + index_in_cluster * 512,
512 * acb->cur_nr_sectors);
ret = qcow2_schedule_bh(qcow2_aio_read_bh, acb);
if (ret < 0)
goto done;
} else {
if ((acb->cluster_offset & 511) != 0) {
ret = -EIO;
goto done;
}
if (s->crypt_method) {
/*
* For encrypted images, read everything into a temporary
* contiguous buffer on which the AES functions can work.
*/
if (!acb->cluster_data) {
acb->cluster_data =
qemu_mallocz(QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
}
assert(acb->cur_nr_sectors <=
QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors);
qemu_iovec_reset(&acb->hd_qiov);
qemu_iovec_add(&acb->hd_qiov, acb->cluster_data,
512 * acb->cur_nr_sectors);
}
BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
acb->hd_aiocb = bdrv_aio_readv(bs->file,
(acb->cluster_offset >> 9) + index_in_cluster,
&acb->hd_qiov, acb->cur_nr_sectors,
qcow2_aio_read_cb, acb);
if (acb->hd_aiocb == NULL) {
ret = -EIO;
goto done;
}
}
return;
done:
acb->common.cb(acb->common.opaque, ret);
qemu_iovec_destroy(&acb->hd_qiov);
qemu_aio_release(acb);
}
static QCowAIOCB *qcow2_aio_setup(BlockDriverState *bs, int64_t sector_num,
QEMUIOVector *qiov, int nb_sectors,
BlockDriverCompletionFunc *cb,
void *opaque, int is_write)
{
QCowAIOCB *acb;
acb = qemu_aio_get(&qcow2_aio_pool, bs, cb, opaque);
if (!acb)
return NULL;
acb->hd_aiocb = NULL;
acb->sector_num = sector_num;
acb->qiov = qiov;
qemu_iovec_init(&acb->hd_qiov, qiov->niov);
acb->bytes_done = 0;
acb->remaining_sectors = nb_sectors;
acb->cur_nr_sectors = 0;
acb->cluster_offset = 0;
acb->l2meta.nb_clusters = 0;
QLIST_INIT(&acb->l2meta.dependent_requests);
return acb;
}
static BlockDriverAIOCB *qcow2_aio_readv(BlockDriverState *bs,
int64_t sector_num,
QEMUIOVector *qiov, int nb_sectors,
BlockDriverCompletionFunc *cb,
void *opaque)
{
QCowAIOCB *acb;
acb = qcow2_aio_setup(bs, sector_num, qiov, nb_sectors, cb, opaque, 0);
if (!acb)
return NULL;
qcow2_aio_read_cb(acb, 0);
return &acb->common;
}
static void qcow2_aio_write_cb(void *opaque, int ret);
static void run_dependent_requests(QCowL2Meta *m)
{
QCowAIOCB *req;
QCowAIOCB *next;
/* Take the request off the list of running requests */
if (m->nb_clusters != 0) {
QLIST_REMOVE(m, next_in_flight);
}
/* Restart all dependent requests */
QLIST_FOREACH_SAFE(req, &m->dependent_requests, next_depend, next) {
qcow2_aio_write_cb(req, 0);
}
/* Empty the list for the next part of the request */
QLIST_INIT(&m->dependent_requests);
}
static void qcow2_aio_write_cb(void *opaque, int ret)
{
QCowAIOCB *acb = opaque;
BlockDriverState *bs = acb->common.bs;
BDRVQcowState *s = bs->opaque;
int index_in_cluster;
int n_end;
acb->hd_aiocb = NULL;
if (ret >= 0) {
ret = qcow2_alloc_cluster_link_l2(bs, &acb->l2meta);
}
run_dependent_requests(&acb->l2meta);
if (ret < 0)
goto done;
acb->remaining_sectors -= acb->cur_nr_sectors;
acb->sector_num += acb->cur_nr_sectors;
acb->bytes_done += acb->cur_nr_sectors * 512;
if (acb->remaining_sectors == 0) {
/* request completed */
ret = 0;
goto done;
}
index_in_cluster = acb->sector_num & (s->cluster_sectors - 1);
n_end = index_in_cluster + acb->remaining_sectors;
if (s->crypt_method &&
n_end > QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors)
n_end = QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors;
ret = qcow2_alloc_cluster_offset(bs, acb->sector_num << 9,
index_in_cluster, n_end, &acb->cur_nr_sectors, &acb->l2meta);
if (ret < 0) {
goto done;
}
acb->cluster_offset = acb->l2meta.cluster_offset;
/* Need to wait for another request? If so, we are done for now. */
if (acb->l2meta.nb_clusters == 0 && acb->l2meta.depends_on != NULL) {
QLIST_INSERT_HEAD(&acb->l2meta.depends_on->dependent_requests,
acb, next_depend);
return;
}
assert((acb->cluster_offset & 511) == 0);
qemu_iovec_reset(&acb->hd_qiov);
qemu_iovec_copy(&acb->hd_qiov, acb->qiov, acb->bytes_done,
acb->cur_nr_sectors * 512);
if (s->crypt_method) {
if (!acb->cluster_data) {
acb->cluster_data = qemu_mallocz(QCOW_MAX_CRYPT_CLUSTERS *
s->cluster_size);
}
assert(acb->hd_qiov.size <= QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
qemu_iovec_to_buffer(&acb->hd_qiov, acb->cluster_data);
qcow2_encrypt_sectors(s, acb->sector_num, acb->cluster_data,
acb->cluster_data, acb->cur_nr_sectors, 1, &s->aes_encrypt_key);
qemu_iovec_reset(&acb->hd_qiov);
qemu_iovec_add(&acb->hd_qiov, acb->cluster_data,
acb->cur_nr_sectors * 512);
}
BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
acb->hd_aiocb = bdrv_aio_writev(bs->file,
(acb->cluster_offset >> 9) + index_in_cluster,
&acb->hd_qiov, acb->cur_nr_sectors,
qcow2_aio_write_cb, acb);
if (acb->hd_aiocb == NULL) {
ret = -EIO;
goto fail;
}
return;
fail:
if (acb->l2meta.nb_clusters != 0) {
QLIST_REMOVE(&acb->l2meta, next_in_flight);
}
done:
acb->common.cb(acb->common.opaque, ret);
qemu_iovec_destroy(&acb->hd_qiov);
qemu_aio_release(acb);
}
static BlockDriverAIOCB *qcow2_aio_writev(BlockDriverState *bs,
int64_t sector_num,
QEMUIOVector *qiov, int nb_sectors,
BlockDriverCompletionFunc *cb,
void *opaque)
{
BDRVQcowState *s = bs->opaque;
QCowAIOCB *acb;
s->cluster_cache_offset = -1; /* disable compressed cache */
acb = qcow2_aio_setup(bs, sector_num, qiov, nb_sectors, cb, opaque, 1);
if (!acb)
return NULL;
qcow2_aio_write_cb(acb, 0);
return &acb->common;
}
static void qcow2_close(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
qemu_free(s->l1_table);
qcow2_cache_flush(bs, s->l2_table_cache);
qcow2_cache_flush(bs, s->refcount_block_cache);
qcow2_cache_destroy(bs, s->l2_table_cache);
qcow2_cache_destroy(bs, s->refcount_block_cache);
qemu_free(s->cluster_cache);
qemu_free(s->cluster_data);
qcow2_refcount_close(bs);
}
/*
* Updates the variable length parts of the qcow2 header, i.e. the backing file
* name and all extensions. qcow2 was not designed to allow such changes, so if
* we run out of space (we can only use the first cluster) this function may
* fail.
*
* Returns 0 on success, -errno in error cases.
*/
static int qcow2_update_ext_header(BlockDriverState *bs,
const char *backing_file, const char *backing_fmt)
{
size_t backing_file_len = 0;
size_t backing_fmt_len = 0;
BDRVQcowState *s = bs->opaque;
QCowExtension ext_backing_fmt = {0, 0};
int ret;
/* Backing file format doesn't make sense without a backing file */
if (backing_fmt && !backing_file) {
return -EINVAL;
}
/* Prepare the backing file format extension if needed */
if (backing_fmt) {
ext_backing_fmt.len = cpu_to_be32(strlen(backing_fmt));
ext_backing_fmt.magic = cpu_to_be32(QCOW2_EXT_MAGIC_BACKING_FORMAT);
backing_fmt_len = ((sizeof(ext_backing_fmt)
+ strlen(backing_fmt) + 7) & ~7);
}
/* Check if we can fit the new header into the first cluster */
if (backing_file) {
backing_file_len = strlen(backing_file);
}
size_t header_size = sizeof(QCowHeader) + backing_file_len
+ backing_fmt_len;
if (header_size > s->cluster_size) {
return -ENOSPC;
}
/* Rewrite backing file name and qcow2 extensions */
size_t ext_size = header_size - sizeof(QCowHeader);
uint8_t buf[ext_size];
size_t offset = 0;
size_t backing_file_offset = 0;
if (backing_file) {
if (backing_fmt) {
int padding = backing_fmt_len -
(sizeof(ext_backing_fmt) + strlen(backing_fmt));
memcpy(buf + offset, &ext_backing_fmt, sizeof(ext_backing_fmt));
offset += sizeof(ext_backing_fmt);
memcpy(buf + offset, backing_fmt, strlen(backing_fmt));
offset += strlen(backing_fmt);
memset(buf + offset, 0, padding);
offset += padding;
}
memcpy(buf + offset, backing_file, backing_file_len);
backing_file_offset = sizeof(QCowHeader) + offset;
}
ret = bdrv_pwrite_sync(bs->file, sizeof(QCowHeader), buf, ext_size);
if (ret < 0) {
goto fail;
}
/* Update header fields */
uint64_t be_backing_file_offset = cpu_to_be64(backing_file_offset);
uint32_t be_backing_file_size = cpu_to_be32(backing_file_len);
ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, backing_file_offset),
&be_backing_file_offset, sizeof(uint64_t));
if (ret < 0) {
goto fail;
}
ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, backing_file_size),
&be_backing_file_size, sizeof(uint32_t));
if (ret < 0) {
goto fail;
}
ret = 0;
fail:
return ret;
}
static int qcow2_change_backing_file(BlockDriverState *bs,
const char *backing_file, const char *backing_fmt)
{
return qcow2_update_ext_header(bs, backing_file, backing_fmt);
}
static int preallocate(BlockDriverState *bs)
{
uint64_t nb_sectors;
uint64_t offset;
int num;
int ret;
QCowL2Meta meta;
nb_sectors = bdrv_getlength(bs) >> 9;
offset = 0;
QLIST_INIT(&meta.dependent_requests);
meta.cluster_offset = 0;
while (nb_sectors) {
num = MIN(nb_sectors, INT_MAX >> 9);
ret = qcow2_alloc_cluster_offset(bs, offset, 0, num, &num, &meta);
if (ret < 0) {
return ret;
}
ret = qcow2_alloc_cluster_link_l2(bs, &meta);
if (ret < 0) {
qcow2_free_any_clusters(bs, meta.cluster_offset, meta.nb_clusters);
return ret;
}
/* There are no dependent requests, but we need to remove our request
* from the list of in-flight requests */
run_dependent_requests(&meta);
/* TODO Preallocate data if requested */
nb_sectors -= num;
offset += num << 9;
}
/*
* It is expected that the image file is large enough to actually contain
* all of the allocated clusters (otherwise we get failing reads after
* EOF). Extend the image to the last allocated sector.
*/
if (meta.cluster_offset != 0) {
uint8_t buf[512];
memset(buf, 0, 512);
ret = bdrv_write(bs->file, (meta.cluster_offset >> 9) + num - 1, buf, 1);
if (ret < 0) {
return ret;
}
}
return 0;
}
static int qcow2_create2(const char *filename, int64_t total_size,
const char *backing_file, const char *backing_format,
int flags, size_t cluster_size, int prealloc,
QEMUOptionParameter *options)
{
/* Calulate cluster_bits */
int cluster_bits;
cluster_bits = ffs(cluster_size) - 1;
if (cluster_bits < MIN_CLUSTER_BITS || cluster_bits > MAX_CLUSTER_BITS ||
(1 << cluster_bits) != cluster_size)
{
error_report(
"Cluster size must be a power of two between %d and %dk\n",
1 << MIN_CLUSTER_BITS, 1 << (MAX_CLUSTER_BITS - 10));
return -EINVAL;
}
/*
* Open the image file and write a minimal qcow2 header.
*
* We keep things simple and start with a zero-sized image. We also
* do without refcount blocks or a L1 table for now. We'll fix the
* inconsistency later.
*
* We do need a refcount table because growing the refcount table means
* allocating two new refcount blocks - the seconds of which would be at
* 2 GB for 64k clusters, and we don't want to have a 2 GB initial file
* size for any qcow2 image.
*/
BlockDriverState* bs;
QCowHeader header;
uint8_t* refcount_table;
int ret;
ret = bdrv_create_file(filename, options);
if (ret < 0) {
return ret;
}
ret = bdrv_file_open(&bs, filename, BDRV_O_RDWR);
if (ret < 0) {
return ret;
}
/* Write the header */
memset(&header, 0, sizeof(header));
header.magic = cpu_to_be32(QCOW_MAGIC);
header.version = cpu_to_be32(QCOW_VERSION);
header.cluster_bits = cpu_to_be32(cluster_bits);
header.size = cpu_to_be64(0);
header.l1_table_offset = cpu_to_be64(0);
header.l1_size = cpu_to_be32(0);
header.refcount_table_offset = cpu_to_be64(cluster_size);
header.refcount_table_clusters = cpu_to_be32(1);
if (flags & BLOCK_FLAG_ENCRYPT) {
header.crypt_method = cpu_to_be32(QCOW_CRYPT_AES);
} else {
header.crypt_method = cpu_to_be32(QCOW_CRYPT_NONE);
}
ret = bdrv_pwrite(bs, 0, &header, sizeof(header));
if (ret < 0) {
goto out;
}
/* Write an empty refcount table */
refcount_table = qemu_mallocz(cluster_size);
ret = bdrv_pwrite(bs, cluster_size, refcount_table, cluster_size);
qemu_free(refcount_table);
if (ret < 0) {
goto out;
}
bdrv_close(bs);
/*
* And now open the image and make it consistent first (i.e. increase the
* refcount of the cluster that is occupied by the header and the refcount
* table)
*/
BlockDriver* drv = bdrv_find_format("qcow2");
assert(drv != NULL);
ret = bdrv_open(bs, filename, BDRV_O_RDWR | BDRV_O_NO_FLUSH, drv);
if (ret < 0) {
goto out;
}
ret = qcow2_alloc_clusters(bs, 2 * cluster_size);
if (ret < 0) {
goto out;
} else if (ret != 0) {
error_report("Huh, first cluster in empty image is already in use?");
abort();
}
/* Okay, now that we have a valid image, let's give it the right size */
ret = bdrv_truncate(bs, total_size * BDRV_SECTOR_SIZE);
if (ret < 0) {
goto out;
}
/* Want a backing file? There you go.*/
if (backing_file) {
ret = bdrv_change_backing_file(bs, backing_file, backing_format);
if (ret < 0) {
goto out;
}
}
/* And if we're supposed to preallocate metadata, do that now */
if (prealloc) {
ret = preallocate(bs);
if (ret < 0) {
goto out;
}
}
ret = 0;
out:
bdrv_delete(bs);
return ret;
}
static int qcow2_create(const char *filename, QEMUOptionParameter *options)
{
const char *backing_file = NULL;
const char *backing_fmt = NULL;
uint64_t sectors = 0;
int flags = 0;
size_t cluster_size = 65536;
int prealloc = 0;
/* Read out options */
while (options && options->name) {
if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
sectors = options->value.n / 512;
} 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_ENCRYPT)) {
flags |= options->value.n ? BLOCK_FLAG_ENCRYPT : 0;
} 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_PREALLOC)) {
if (!options->value.s || !strcmp(options->value.s, "off")) {
prealloc = 0;
} else if (!strcmp(options->value.s, "metadata")) {
prealloc = 1;
} else {
fprintf(stderr, "Invalid preallocation mode: '%s'\n",
options->value.s);
return -EINVAL;
}
}
options++;
}
if (backing_file && prealloc) {
fprintf(stderr, "Backing file and preallocation cannot be used at "
"the same time\n");
return -EINVAL;
}
return qcow2_create2(filename, sectors, backing_file, backing_fmt, flags,
cluster_size, prealloc, options);
}
static int qcow2_make_empty(BlockDriverState *bs)
{
#if 0
/* XXX: not correct */
BDRVQcowState *s = bs->opaque;
uint32_t l1_length = s->l1_size * sizeof(uint64_t);
int ret;
memset(s->l1_table, 0, l1_length);
if (bdrv_pwrite(bs->file, s->l1_table_offset, s->l1_table, l1_length) < 0)
return -1;
ret = bdrv_truncate(bs->file, s->l1_table_offset + l1_length);
if (ret < 0)
return ret;
l2_cache_reset(bs);
#endif
return 0;
}
static int qcow2_discard(BlockDriverState *bs, int64_t sector_num,
int nb_sectors)
{
return qcow2_discard_clusters(bs, sector_num << BDRV_SECTOR_BITS,
nb_sectors);
}
static int qcow2_truncate(BlockDriverState *bs, int64_t offset)
{
BDRVQcowState *s = bs->opaque;
int ret, new_l1_size;
if (offset & 511) {
return -EINVAL;
}
/* cannot proceed if image has snapshots */
if (s->nb_snapshots) {
return -ENOTSUP;
}
/* shrinking is currently not supported */
if (offset < bs->total_sectors * 512) {
return -ENOTSUP;
}
new_l1_size = size_to_l1(s, offset);
ret = qcow2_grow_l1_table(bs, new_l1_size, true);
if (ret < 0) {
return ret;
}
/* write updated header.size */
offset = cpu_to_be64(offset);
ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, size),
&offset, sizeof(uint64_t));
if (ret < 0) {
return ret;
}
s->l1_vm_state_index = new_l1_size;
return 0;
}
/* XXX: put compressed sectors first, then all the cluster aligned
tables to avoid losing bytes in alignment */
static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num,
const uint8_t *buf, int nb_sectors)
{
BDRVQcowState *s = bs->opaque;
z_stream strm;
int ret, out_len;
uint8_t *out_buf;
uint64_t cluster_offset;
if (nb_sectors == 0) {
/* align end of file to a sector boundary to ease reading with
sector based I/Os */
cluster_offset = bdrv_getlength(bs->file);
cluster_offset = (cluster_offset + 511) & ~511;
bdrv_truncate(bs->file, cluster_offset);
return 0;
}
if (nb_sectors != s->cluster_sectors)
return -EINVAL;
out_buf = qemu_malloc(s->cluster_size + (s->cluster_size / 1000) + 128);
/* best compression, small window, no zlib header */
memset(&strm, 0, sizeof(strm));
ret = deflateInit2(&strm, Z_DEFAULT_COMPRESSION,
Z_DEFLATED, -12,
9, Z_DEFAULT_STRATEGY);
if (ret != 0) {
qemu_free(out_buf);
return -1;
}
strm.avail_in = s->cluster_size;
strm.next_in = (uint8_t *)buf;
strm.avail_out = s->cluster_size;
strm.next_out = out_buf;
ret = deflate(&strm, Z_FINISH);
if (ret != Z_STREAM_END && ret != Z_OK) {
qemu_free(out_buf);
deflateEnd(&strm);
return -1;
}
out_len = strm.next_out - out_buf;
deflateEnd(&strm);
if (ret != Z_STREAM_END || out_len >= s->cluster_size) {
/* could not compress: write normal cluster */
bdrv_write(bs, sector_num, buf, s->cluster_sectors);
} else {
cluster_offset = qcow2_alloc_compressed_cluster_offset(bs,
sector_num << 9, out_len);
if (!cluster_offset)
return -1;
cluster_offset &= s->cluster_offset_mask;
BLKDBG_EVENT(bs->file, BLKDBG_WRITE_COMPRESSED);
if (bdrv_pwrite(bs->file, cluster_offset, out_buf, out_len) != out_len) {
qemu_free(out_buf);
return -1;
}
}
qemu_free(out_buf);
return 0;
}
static int qcow2_flush(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
int ret;
ret = qcow2_cache_flush(bs, s->l2_table_cache);
if (ret < 0) {
return ret;
}
ret = qcow2_cache_flush(bs, s->refcount_block_cache);
if (ret < 0) {
return ret;
}
return bdrv_flush(bs->file);
}
static BlockDriverAIOCB *qcow2_aio_flush(BlockDriverState *bs,
BlockDriverCompletionFunc *cb,
void *opaque)
{
BDRVQcowState *s = bs->opaque;
int ret;
ret = qcow2_cache_flush(bs, s->l2_table_cache);
if (ret < 0) {
return NULL;
}
ret = qcow2_cache_flush(bs, s->refcount_block_cache);
if (ret < 0) {
return NULL;
}
return bdrv_aio_flush(bs->file, cb, opaque);
}
static int64_t qcow2_vm_state_offset(BDRVQcowState *s)
{
return (int64_t)s->l1_vm_state_index << (s->cluster_bits + s->l2_bits);
}
static int qcow2_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
{
BDRVQcowState *s = bs->opaque;
bdi->cluster_size = s->cluster_size;
bdi->vm_state_offset = qcow2_vm_state_offset(s);
return 0;
}
static int qcow2_check(BlockDriverState *bs, BdrvCheckResult *result)
{
return qcow2_check_refcounts(bs, result);
}
#if 0
static void dump_refcounts(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
int64_t nb_clusters, k, k1, size;
int refcount;
size = bdrv_getlength(bs->file);
nb_clusters = size_to_clusters(s, size);
for(k = 0; k < nb_clusters;) {
k1 = k;
refcount = get_refcount(bs, k);
k++;
while (k < nb_clusters && get_refcount(bs, k) == refcount)
k++;
printf("%" PRId64 ": refcount=%d nb=%" PRId64 "\n", k, refcount,
k - k1);
}
}
#endif
static int qcow2_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
int64_t pos, int size)
{
BDRVQcowState *s = bs->opaque;
int growable = bs->growable;
int ret;
BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE);
bs->growable = 1;
ret = bdrv_pwrite(bs, qcow2_vm_state_offset(s) + pos, buf, size);
bs->growable = growable;
return ret;
}
static int qcow2_load_vmstate(BlockDriverState *bs, uint8_t *buf,
int64_t pos, int size)
{
BDRVQcowState *s = bs->opaque;
int growable = bs->growable;
int ret;
BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_LOAD);
bs->growable = 1;
ret = bdrv_pread(bs, qcow2_vm_state_offset(s) + pos, buf, size);
bs->growable = growable;
return ret;
}
static QEMUOptionParameter qcow2_create_options[] = {
{
.name = BLOCK_OPT_SIZE,
.type = OPT_SIZE,
.help = "Virtual disk size"
},
{
.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_ENCRYPT,
.type = OPT_FLAG,
.help = "Encrypt the image"
},
{
.name = BLOCK_OPT_CLUSTER_SIZE,
.type = OPT_SIZE,
.help = "qcow2 cluster size"
},
{
.name = BLOCK_OPT_PREALLOC,
.type = OPT_STRING,
.help = "Preallocation mode (allowed values: off, metadata)"
},
{ NULL }
};
static BlockDriver bdrv_qcow2 = {
.format_name = "qcow2",
.instance_size = sizeof(BDRVQcowState),
.bdrv_probe = qcow2_probe,
.bdrv_open = qcow2_open,
.bdrv_close = qcow2_close,
.bdrv_create = qcow2_create,
.bdrv_flush = qcow2_flush,
.bdrv_is_allocated = qcow2_is_allocated,
.bdrv_set_key = qcow2_set_key,
.bdrv_make_empty = qcow2_make_empty,
.bdrv_aio_readv = qcow2_aio_readv,
.bdrv_aio_writev = qcow2_aio_writev,
.bdrv_aio_flush = qcow2_aio_flush,
.bdrv_discard = qcow2_discard,
.bdrv_truncate = qcow2_truncate,
.bdrv_write_compressed = qcow2_write_compressed,
.bdrv_snapshot_create = qcow2_snapshot_create,
.bdrv_snapshot_goto = qcow2_snapshot_goto,
.bdrv_snapshot_delete = qcow2_snapshot_delete,
.bdrv_snapshot_list = qcow2_snapshot_list,
.bdrv_snapshot_load_tmp = qcow2_snapshot_load_tmp,
.bdrv_get_info = qcow2_get_info,
.bdrv_save_vmstate = qcow2_save_vmstate,
.bdrv_load_vmstate = qcow2_load_vmstate,
.bdrv_change_backing_file = qcow2_change_backing_file,
.create_options = qcow2_create_options,
.bdrv_check = qcow2_check,
};
static void bdrv_qcow2_init(void)
{
bdrv_register(&bdrv_qcow2);
}
block_init(bdrv_qcow2_init);
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