qcow2: Implement .bdrv_co_preadv()

[qemu.git] / block / qcow2.h

/*
 * 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.
 */

#ifndef BLOCK_QCOW2_H
#define BLOCK_QCOW2_H

#include "crypto/cipher.h"
#include "qemu/coroutine.h"

//#define DEBUG_ALLOC
//#define DEBUG_ALLOC2
//#define DEBUG_EXT

#define QCOW_MAGIC (('Q' << 24) | ('F' << 16) | ('I' << 8) | 0xfb)

#define QCOW_CRYPT_NONE 0
#define QCOW_CRYPT_AES  1

#define QCOW_MAX_CRYPT_CLUSTERS 32
#define QCOW_MAX_SNAPSHOTS 65536

/* 8 MB refcount table is enough for 2 PB images at 64k cluster size
 * (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
#define QCOW_MAX_REFTABLE_SIZE 0x800000

/* 32 MB L1 table is enough for 2 PB images at 64k cluster size
 * (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
#define QCOW_MAX_L1_SIZE 0x2000000

/* Allow for an average of 1k per snapshot table entry, should be plenty of
 * space for snapshot names and IDs */
#define QCOW_MAX_SNAPSHOTS_SIZE (1024 * QCOW_MAX_SNAPSHOTS)

/* indicate that the refcount of the referenced cluster is exactly one. */
#define QCOW_OFLAG_COPIED     (1ULL << 63)
/* indicate that the cluster is compressed (they never have the copied flag) */
#define QCOW_OFLAG_COMPRESSED (1ULL << 62)
/* The cluster reads as all zeros */
#define QCOW_OFLAG_ZERO (1ULL << 0)

#define MIN_CLUSTER_BITS 9
#define MAX_CLUSTER_BITS 21

/* Must be at least 2 to cover COW */
#define MIN_L2_CACHE_SIZE 2 /* clusters */

/* Must be at least 4 to cover all cases of refcount table growth */
#define MIN_REFCOUNT_CACHE_SIZE 4 /* clusters */

/* Whichever is more */
#define DEFAULT_L2_CACHE_CLUSTERS 8 /* clusters */
#define DEFAULT_L2_CACHE_BYTE_SIZE 1048576 /* bytes */

/* The refblock cache needs only a fourth of the L2 cache size to cover as many
 * clusters */
#define DEFAULT_L2_REFCOUNT_SIZE_RATIO 4

#define DEFAULT_CLUSTER_SIZE 65536


#define QCOW2_OPT_LAZY_REFCOUNTS "lazy-refcounts"
#define QCOW2_OPT_DISCARD_REQUEST "pass-discard-request"
#define QCOW2_OPT_DISCARD_SNAPSHOT "pass-discard-snapshot"
#define QCOW2_OPT_DISCARD_OTHER "pass-discard-other"
#define QCOW2_OPT_OVERLAP "overlap-check"
#define QCOW2_OPT_OVERLAP_TEMPLATE "overlap-check.template"
#define QCOW2_OPT_OVERLAP_MAIN_HEADER "overlap-check.main-header"
#define QCOW2_OPT_OVERLAP_ACTIVE_L1 "overlap-check.active-l1"
#define QCOW2_OPT_OVERLAP_ACTIVE_L2 "overlap-check.active-l2"
#define QCOW2_OPT_OVERLAP_REFCOUNT_TABLE "overlap-check.refcount-table"
#define QCOW2_OPT_OVERLAP_REFCOUNT_BLOCK "overlap-check.refcount-block"
#define QCOW2_OPT_OVERLAP_SNAPSHOT_TABLE "overlap-check.snapshot-table"
#define QCOW2_OPT_OVERLAP_INACTIVE_L1 "overlap-check.inactive-l1"
#define QCOW2_OPT_OVERLAP_INACTIVE_L2 "overlap-check.inactive-l2"
#define QCOW2_OPT_CACHE_SIZE "cache-size"
#define QCOW2_OPT_L2_CACHE_SIZE "l2-cache-size"
#define QCOW2_OPT_REFCOUNT_CACHE_SIZE "refcount-cache-size"
#define QCOW2_OPT_CACHE_CLEAN_INTERVAL "cache-clean-interval"

typedef struct QCowHeader {
    uint32_t magic;
    uint32_t version;
    uint64_t backing_file_offset;
    uint32_t backing_file_size;
    uint32_t cluster_bits;
    uint64_t size; /* in bytes */
    uint32_t crypt_method;
    uint32_t l1_size; /* XXX: save number of clusters instead ? */
    uint64_t l1_table_offset;
    uint64_t refcount_table_offset;
    uint32_t refcount_table_clusters;
    uint32_t nb_snapshots;
    uint64_t snapshots_offset;

    /* The following fields are only valid for version >= 3 */
    uint64_t incompatible_features;
    uint64_t compatible_features;
    uint64_t autoclear_features;

    uint32_t refcount_order;
    uint32_t header_length;
} QEMU_PACKED QCowHeader;

typedef struct QEMU_PACKED QCowSnapshotHeader {
    /* header is 8 byte aligned */
    uint64_t l1_table_offset;

    uint32_t l1_size;
    uint16_t id_str_size;
    uint16_t name_size;

    uint32_t date_sec;
    uint32_t date_nsec;

    uint64_t vm_clock_nsec;

    uint32_t vm_state_size;
    uint32_t extra_data_size; /* for extension */
    /* extra data follows */
    /* id_str follows */
    /* name follows  */
} QCowSnapshotHeader;

typedef struct QEMU_PACKED QCowSnapshotExtraData {
    uint64_t vm_state_size_large;
    uint64_t disk_size;
} QCowSnapshotExtraData;


typedef struct QCowSnapshot {
    uint64_t l1_table_offset;
    uint32_t l1_size;
    char *id_str;
    char *name;
    uint64_t disk_size;
    uint64_t vm_state_size;
    uint32_t date_sec;
    uint32_t date_nsec;
    uint64_t vm_clock_nsec;
} QCowSnapshot;

struct Qcow2Cache;
typedef struct Qcow2Cache Qcow2Cache;

typedef struct Qcow2UnknownHeaderExtension {
    uint32_t magic;
    uint32_t len;
    QLIST_ENTRY(Qcow2UnknownHeaderExtension) next;
    uint8_t data[];
} Qcow2UnknownHeaderExtension;

enum {
    QCOW2_FEAT_TYPE_INCOMPATIBLE    = 0,
    QCOW2_FEAT_TYPE_COMPATIBLE      = 1,
    QCOW2_FEAT_TYPE_AUTOCLEAR       = 2,
};

/* Incompatible feature bits */
enum {
    QCOW2_INCOMPAT_DIRTY_BITNR   = 0,
    QCOW2_INCOMPAT_CORRUPT_BITNR = 1,
    QCOW2_INCOMPAT_DIRTY         = 1 << QCOW2_INCOMPAT_DIRTY_BITNR,
    QCOW2_INCOMPAT_CORRUPT       = 1 << QCOW2_INCOMPAT_CORRUPT_BITNR,

    QCOW2_INCOMPAT_MASK          = QCOW2_INCOMPAT_DIRTY
                                 | QCOW2_INCOMPAT_CORRUPT,
};

/* Compatible feature bits */
enum {
    QCOW2_COMPAT_LAZY_REFCOUNTS_BITNR = 0,
    QCOW2_COMPAT_LAZY_REFCOUNTS       = 1 << QCOW2_COMPAT_LAZY_REFCOUNTS_BITNR,

    QCOW2_COMPAT_FEAT_MASK            = QCOW2_COMPAT_LAZY_REFCOUNTS,
};

enum qcow2_discard_type {
    QCOW2_DISCARD_NEVER = 0,
    QCOW2_DISCARD_ALWAYS,
    QCOW2_DISCARD_REQUEST,
    QCOW2_DISCARD_SNAPSHOT,
    QCOW2_DISCARD_OTHER,
    QCOW2_DISCARD_MAX
};

typedef struct Qcow2Feature {
    uint8_t type;
    uint8_t bit;
    char    name[46];
} QEMU_PACKED Qcow2Feature;

typedef struct Qcow2DiscardRegion {
    BlockDriverState *bs;
    uint64_t offset;
    uint64_t bytes;
    QTAILQ_ENTRY(Qcow2DiscardRegion) next;
} Qcow2DiscardRegion;

typedef uint64_t Qcow2GetRefcountFunc(const void *refcount_array,
                                      uint64_t index);
typedef void Qcow2SetRefcountFunc(void *refcount_array,
                                  uint64_t index, uint64_t value);

typedef struct BDRVQcow2State {
    int cluster_bits;
    int cluster_size;
    int cluster_sectors;
    int l2_bits;
    int l2_size;
    int l1_size;
    int l1_vm_state_index;
    int refcount_block_bits;
    int refcount_block_size;
    int csize_shift;
    int csize_mask;
    uint64_t cluster_offset_mask;
    uint64_t l1_table_offset;
    uint64_t *l1_table;

    Qcow2Cache* l2_table_cache;
    Qcow2Cache* refcount_block_cache;
    QEMUTimer *cache_clean_timer;
    unsigned cache_clean_interval;

    uint8_t *cluster_cache;
    uint8_t *cluster_data;
    uint64_t cluster_cache_offset;
    QLIST_HEAD(QCowClusterAlloc, QCowL2Meta) cluster_allocs;

    uint64_t *refcount_table;
    uint64_t refcount_table_offset;
    uint32_t refcount_table_size;
    uint64_t free_cluster_index;
    uint64_t free_byte_offset;

    CoMutex lock;

    QCryptoCipher *cipher; /* current cipher, NULL if no key yet */
    uint32_t crypt_method_header;
    uint64_t snapshots_offset;
    int snapshots_size;
    unsigned int nb_snapshots;
    QCowSnapshot *snapshots;

    int flags;
    int qcow_version;
    bool use_lazy_refcounts;
    int refcount_order;
    int refcount_bits;
    uint64_t refcount_max;

    Qcow2GetRefcountFunc *get_refcount;
    Qcow2SetRefcountFunc *set_refcount;

    bool discard_passthrough[QCOW2_DISCARD_MAX];

    int overlap_check; /* bitmask of Qcow2MetadataOverlap values */
    bool signaled_corruption;

    uint64_t incompatible_features;
    uint64_t compatible_features;
    uint64_t autoclear_features;

    size_t unknown_header_fields_size;
    void* unknown_header_fields;
    QLIST_HEAD(, Qcow2UnknownHeaderExtension) unknown_header_ext;
    QTAILQ_HEAD (, Qcow2DiscardRegion) discards;
    bool cache_discards;

    /* Backing file path and format as stored in the image (this is not the
     * effective path/format, which may be the result of a runtime option
     * override) */
    char *image_backing_file;
    char *image_backing_format;
} BDRVQcow2State;

typedef struct Qcow2COWRegion {
    /**
     * Offset of the COW region in bytes from the start of the first cluster
     * touched by the request.
     */
    uint64_t    offset;

    /** Number of sectors to copy */
    int         nb_sectors;
} Qcow2COWRegion;

/**
 * Describes an in-flight (part of a) write request that writes to clusters
 * that are not referenced in their L2 table yet.
 */
typedef struct QCowL2Meta
{
    /** Guest offset of the first newly allocated cluster */
    uint64_t offset;

    /** Host offset of the first newly allocated cluster */
    uint64_t alloc_offset;

    /**
     * Number of sectors from the start of the first allocated cluster to
     * the end of the (possibly shortened) request
     */
    int nb_available;

    /** Number of newly allocated clusters */
    int nb_clusters;

    /**
     * Requests that overlap with this allocation and wait to be restarted
     * when the allocating request has completed.
     */
    CoQueue dependent_requests;

    /**
     * The COW Region between the start of the first allocated cluster and the
     * area the guest actually writes to.
     */
    Qcow2COWRegion cow_start;

    /**
     * The COW Region between the area the guest actually writes to and the
     * end of the last allocated cluster.
     */
    Qcow2COWRegion cow_end;

    /** Pointer to next L2Meta of the same write request */
    struct QCowL2Meta *next;

    QLIST_ENTRY(QCowL2Meta) next_in_flight;
} QCowL2Meta;

enum {
    QCOW2_CLUSTER_UNALLOCATED,
    QCOW2_CLUSTER_NORMAL,
    QCOW2_CLUSTER_COMPRESSED,
    QCOW2_CLUSTER_ZERO
};

typedef enum QCow2MetadataOverlap {
    QCOW2_OL_MAIN_HEADER_BITNR    = 0,
    QCOW2_OL_ACTIVE_L1_BITNR      = 1,
    QCOW2_OL_ACTIVE_L2_BITNR      = 2,
    QCOW2_OL_REFCOUNT_TABLE_BITNR = 3,
    QCOW2_OL_REFCOUNT_BLOCK_BITNR = 4,
    QCOW2_OL_SNAPSHOT_TABLE_BITNR = 5,
    QCOW2_OL_INACTIVE_L1_BITNR    = 6,
    QCOW2_OL_INACTIVE_L2_BITNR    = 7,

    QCOW2_OL_MAX_BITNR            = 8,

    QCOW2_OL_NONE           = 0,
    QCOW2_OL_MAIN_HEADER    = (1 << QCOW2_OL_MAIN_HEADER_BITNR),
    QCOW2_OL_ACTIVE_L1      = (1 << QCOW2_OL_ACTIVE_L1_BITNR),
    QCOW2_OL_ACTIVE_L2      = (1 << QCOW2_OL_ACTIVE_L2_BITNR),
    QCOW2_OL_REFCOUNT_TABLE = (1 << QCOW2_OL_REFCOUNT_TABLE_BITNR),
    QCOW2_OL_REFCOUNT_BLOCK = (1 << QCOW2_OL_REFCOUNT_BLOCK_BITNR),
    QCOW2_OL_SNAPSHOT_TABLE = (1 << QCOW2_OL_SNAPSHOT_TABLE_BITNR),
    QCOW2_OL_INACTIVE_L1    = (1 << QCOW2_OL_INACTIVE_L1_BITNR),
    /* NOTE: Checking overlaps with inactive L2 tables will result in bdrv
     * reads. */
    QCOW2_OL_INACTIVE_L2    = (1 << QCOW2_OL_INACTIVE_L2_BITNR),
} QCow2MetadataOverlap;

/* Perform all overlap checks which can be done in constant time */
#define QCOW2_OL_CONSTANT \
    (QCOW2_OL_MAIN_HEADER | QCOW2_OL_ACTIVE_L1 | QCOW2_OL_REFCOUNT_TABLE | \
     QCOW2_OL_SNAPSHOT_TABLE)

/* Perform all overlap checks which don't require disk access */
#define QCOW2_OL_CACHED \
    (QCOW2_OL_CONSTANT | QCOW2_OL_ACTIVE_L2 | QCOW2_OL_REFCOUNT_BLOCK | \
     QCOW2_OL_INACTIVE_L1)

/* Perform all overlap checks */
#define QCOW2_OL_ALL \
    (QCOW2_OL_CACHED | QCOW2_OL_INACTIVE_L2)

#define L1E_OFFSET_MASK 0x00fffffffffffe00ULL
#define L2E_OFFSET_MASK 0x00fffffffffffe00ULL
#define L2E_COMPRESSED_OFFSET_SIZE_MASK 0x3fffffffffffffffULL

#define REFT_OFFSET_MASK 0xfffffffffffffe00ULL

static inline int64_t start_of_cluster(BDRVQcow2State *s, int64_t offset)
{
    return offset & ~(s->cluster_size - 1);
}

static inline int64_t offset_into_cluster(BDRVQcow2State *s, int64_t offset)
{
    return offset & (s->cluster_size - 1);
}

static inline uint64_t size_to_clusters(BDRVQcow2State *s, uint64_t size)
{
    return (size + (s->cluster_size - 1)) >> s->cluster_bits;
}

static inline int64_t size_to_l1(BDRVQcow2State *s, int64_t size)
{
    int shift = s->cluster_bits + s->l2_bits;
    return (size + (1ULL << shift) - 1) >> shift;
}

static inline int offset_to_l2_index(BDRVQcow2State *s, int64_t offset)
{
    return (offset >> s->cluster_bits) & (s->l2_size - 1);
}

static inline int64_t align_offset(int64_t offset, int n)
{
    offset = (offset + n - 1) & ~(n - 1);
    return offset;
}

static inline int64_t qcow2_vm_state_offset(BDRVQcow2State *s)
{
    return (int64_t)s->l1_vm_state_index << (s->cluster_bits + s->l2_bits);
}

static inline uint64_t qcow2_max_refcount_clusters(BDRVQcow2State *s)
{
    return QCOW_MAX_REFTABLE_SIZE >> s->cluster_bits;
}

static inline int qcow2_get_cluster_type(uint64_t l2_entry)
{
    if (l2_entry & QCOW_OFLAG_COMPRESSED) {
        return QCOW2_CLUSTER_COMPRESSED;
    } else if (l2_entry & QCOW_OFLAG_ZERO) {
        return QCOW2_CLUSTER_ZERO;
    } else if (!(l2_entry & L2E_OFFSET_MASK)) {
        return QCOW2_CLUSTER_UNALLOCATED;
    } else {
        return QCOW2_CLUSTER_NORMAL;
    }
}

/* Check whether refcounts are eager or lazy */
static inline bool qcow2_need_accurate_refcounts(BDRVQcow2State *s)
{
    return !(s->incompatible_features & QCOW2_INCOMPAT_DIRTY);
}

static inline uint64_t l2meta_cow_start(QCowL2Meta *m)
{
    return m->offset + m->cow_start.offset;
}

static inline uint64_t l2meta_cow_end(QCowL2Meta *m)
{
    return m->offset + m->cow_end.offset
        + (m->cow_end.nb_sectors << BDRV_SECTOR_BITS);
}

static inline uint64_t refcount_diff(uint64_t r1, uint64_t r2)
{
    return r1 > r2 ? r1 - r2 : r2 - r1;
}

// FIXME Need qcow2_ prefix to global functions

/* qcow2.c functions */
int qcow2_backing_read1(BlockDriverState *bs, QEMUIOVector *qiov,
                  int64_t sector_num, int nb_sectors);

int qcow2_mark_dirty(BlockDriverState *bs);
int qcow2_mark_corrupt(BlockDriverState *bs);
int qcow2_mark_consistent(BlockDriverState *bs);
int qcow2_update_header(BlockDriverState *bs);

void qcow2_signal_corruption(BlockDriverState *bs, bool fatal, int64_t offset,
                             int64_t size, const char *message_format, ...)
                             GCC_FMT_ATTR(5, 6);

/* qcow2-refcount.c functions */
int qcow2_refcount_init(BlockDriverState *bs);
void qcow2_refcount_close(BlockDriverState *bs);

int qcow2_get_refcount(BlockDriverState *bs, int64_t cluster_index,
                       uint64_t *refcount);

int qcow2_update_cluster_refcount(BlockDriverState *bs, int64_t cluster_index,
                                  uint64_t addend, bool decrease,
                                  enum qcow2_discard_type type);

int64_t qcow2_alloc_clusters(BlockDriverState *bs, uint64_t size);
int64_t qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
                                int64_t nb_clusters);
int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size);
void qcow2_free_clusters(BlockDriverState *bs,
                          int64_t offset, int64_t size,
                          enum qcow2_discard_type type);
void qcow2_free_any_clusters(BlockDriverState *bs, uint64_t l2_entry,
                             int nb_clusters, enum qcow2_discard_type type);

int qcow2_update_snapshot_refcount(BlockDriverState *bs,
    int64_t l1_table_offset, int l1_size, int addend);

int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
                          BdrvCheckMode fix);

void qcow2_process_discards(BlockDriverState *bs, int ret);

int qcow2_check_metadata_overlap(BlockDriverState *bs, int ign, int64_t offset,
                                 int64_t size);
int qcow2_pre_write_overlap_check(BlockDriverState *bs, int ign, int64_t offset,
                                  int64_t size);

int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order,
                                BlockDriverAmendStatusCB *status_cb,
                                void *cb_opaque, Error **errp);

/* qcow2-cluster.c functions */
int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
                        bool exact_size);
int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index);
void qcow2_l2_cache_reset(BlockDriverState *bs);
int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset);
int qcow2_encrypt_sectors(BDRVQcow2State *s, int64_t sector_num,
                          uint8_t *out_buf, const uint8_t *in_buf,
                          int nb_sectors, bool enc, Error **errp);

int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
                             unsigned int *bytes, uint64_t *cluster_offset);
int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
    int *num, uint64_t *host_offset, QCowL2Meta **m);
uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
                                         uint64_t offset,
                                         int compressed_size);

int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m);
int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
    int nb_sectors, enum qcow2_discard_type type, bool full_discard);
int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors);

int qcow2_expand_zero_clusters(BlockDriverState *bs,
                               BlockDriverAmendStatusCB *status_cb,
                               void *cb_opaque);

/* qcow2-snapshot.c functions */
int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info);
int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id);
int qcow2_snapshot_delete(BlockDriverState *bs,
                          const char *snapshot_id,
                          const char *name,
                          Error **errp);
int qcow2_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab);
int qcow2_snapshot_load_tmp(BlockDriverState *bs,
                            const char *snapshot_id,
                            const char *name,
                            Error **errp);

void qcow2_free_snapshots(BlockDriverState *bs);
int qcow2_read_snapshots(BlockDriverState *bs);

/* qcow2-cache.c functions */
Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables);
int qcow2_cache_destroy(BlockDriverState* bs, Qcow2Cache *c);

void qcow2_cache_entry_mark_dirty(BlockDriverState *bs, Qcow2Cache *c,
     void *table);
int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c);
int qcow2_cache_write(BlockDriverState *bs, Qcow2Cache *c);
int qcow2_cache_set_dependency(BlockDriverState *bs, Qcow2Cache *c,
    Qcow2Cache *dependency);
void qcow2_cache_depends_on_flush(Qcow2Cache *c);

void qcow2_cache_clean_unused(BlockDriverState *bs, Qcow2Cache *c);
int qcow2_cache_empty(BlockDriverState *bs, Qcow2Cache *c);

int qcow2_cache_get(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
    void **table);
int qcow2_cache_get_empty(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
    void **table);
void qcow2_cache_put(BlockDriverState *bs, Qcow2Cache *c, void **table);

#endif