Archipelago » qemu

/*

 * Block driver for the VMDK format

 *

 * Copyright (c) 2004 Fabrice Bellard

 * Copyright (c) 2005 Filip Navara

 *

 * 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 "migration.h"

#include <zlib.h>

#define VMDK3_MAGIC (('C' << 24) | ('O' << 16) | ('W' << 8) | 'D')

#define VMDK4_MAGIC (('K' << 24) | ('D' << 16) | ('M' << 8) | 'V')

#define VMDK4_COMPRESSION_DEFLATE 1

#define VMDK4_FLAG_RGD (1 << 1)

#define VMDK4_FLAG_COMPRESS (1 << 16)

#define VMDK4_FLAG_MARKER (1 << 17)

#define VMDK4_GD_AT_END 0xffffffffffffffffULL

typedef struct {

    uint32_t version;

    uint32_t flags;

    uint32_t disk_sectors;

    uint32_t granularity;

    uint32_t l1dir_offset;

    uint32_t l1dir_size;

    uint32_t file_sectors;

    uint32_t cylinders;

    uint32_t heads;

    uint32_t sectors_per_track;

} VMDK3Header;

typedef struct {

    uint32_t version;

    uint32_t flags;

    int64_t capacity;

    int64_t granularity;

    int64_t desc_offset;

    int64_t desc_size;

    int32_t num_gtes_per_gte;

    int64_t rgd_offset;

    int64_t gd_offset;

    int64_t grain_offset;

    char filler[1];

    char check_bytes[4];

    uint16_t compressAlgorithm;

} QEMU_PACKED VMDK4Header;

#define L2_CACHE_SIZE 16

typedef struct VmdkExtent {

    BlockDriverState *file;

    bool flat;

    bool compressed;

    bool has_marker;

    int64_t sectors;

    int64_t end_sector;

    int64_t flat_start_offset;

    int64_t l1_table_offset;

    int64_t l1_backup_table_offset;

    uint32_t *l1_table;

    uint32_t *l1_backup_table;

    unsigned int l1_size;

    uint32_t l1_entry_sectors;

    unsigned int l2_size;

    uint32_t *l2_cache;

    uint32_t l2_cache_offsets[L2_CACHE_SIZE];

    uint32_t l2_cache_counts[L2_CACHE_SIZE];

    unsigned int cluster_sectors;

} VmdkExtent;

typedef struct BDRVVmdkState {

    CoMutex lock;

    int desc_offset;

    bool cid_updated;

    uint32_t parent_cid;

    int num_extents;

    /* Extent array with num_extents entries, ascend ordered by address */

    VmdkExtent *extents;

    Error *migration_blocker;

} BDRVVmdkState;

typedef struct VmdkMetaData {

    uint32_t offset;

    unsigned int l1_index;

    unsigned int l2_index;

    unsigned int l2_offset;

    int valid;

} VmdkMetaData;

typedef struct VmdkGrainMarker {

    uint64_t lba;

    uint32_t size;

    uint8_t  data[0];

} VmdkGrainMarker;

enum {

    MARKER_END_OF_STREAM    = 0,

    MARKER_GRAIN_TABLE      = 1,

    MARKER_GRAIN_DIRECTORY  = 2,

    MARKER_FOOTER           = 3,

};

static int vmdk_probe(const uint8_t *buf, int buf_size, const char *filename)

{

    uint32_t magic;

    if (buf_size < 4) {

        return 0;

    }

    magic = be32_to_cpu(*(uint32_t *)buf);

    if (magic == VMDK3_MAGIC ||

        magic == VMDK4_MAGIC) {

        return 100;

    } else {

        const char *p = (const char *)buf;

        const char *end = p + buf_size;

        while (p < end) {

            if (*p == '#') {

                /* skip comment line */

                while (p < end && *p != '\n') {

                    p++;

                }

                p++;

                continue;

            }

            if (*p == ' ') {

                while (p < end && *p == ' ') {

                    p++;

                }

                /* skip '\r' if windows line endings used. */

                if (p < end && *p == '\r') {

                    p++;

                }

                /* only accept blank lines before 'version=' line */

                if (p == end || *p != '\n') {

                    return 0;

                }

                p++;

                continue;

            }

            if (end - p >= strlen("version=X\n")) {

                if (strncmp("version=1\n", p, strlen("version=1\n")) == 0 ||

                    strncmp("version=2\n", p, strlen("version=2\n")) == 0) {

                    return 100;

                }

            }

            if (end - p >= strlen("version=X\r\n")) {

                if (strncmp("version=1\r\n", p, strlen("version=1\r\n")) == 0 ||

                    strncmp("version=2\r\n", p, strlen("version=2\r\n")) == 0) {

                    return 100;

                }

            }

            return 0;

        }

        return 0;

    }

}

#define CHECK_CID 1

#define SECTOR_SIZE 512

#define DESC_SIZE (20 * SECTOR_SIZE)    /* 20 sectors of 512 bytes each */

#define BUF_SIZE 4096

#define HEADER_SIZE 512                 /* first sector of 512 bytes */

static void vmdk_free_extents(BlockDriverState *bs)

{

    int i;

    BDRVVmdkState *s = bs->opaque;

    VmdkExtent *e;

    for (i = 0; i < s->num_extents; i++) {

        e = &s->extents[i];

        g_free(e->l1_table);

        g_free(e->l2_cache);

        g_free(e->l1_backup_table);

        if (e->file != bs->file) {

            bdrv_delete(e->file);

        }

    }

    g_free(s->extents);

}

static void vmdk_free_last_extent(BlockDriverState *bs)

{

    BDRVVmdkState *s = bs->opaque;

    if (s->num_extents == 0) {

        return;

    }

    s->num_extents--;

    s->extents = g_realloc(s->extents, s->num_extents * sizeof(VmdkExtent));

}

static uint32_t vmdk_read_cid(BlockDriverState *bs, int parent)

{

    char desc[DESC_SIZE];

    uint32_t cid = 0xffffffff;

    const char *p_name, *cid_str;

    size_t cid_str_size;

    BDRVVmdkState *s = bs->opaque;

    int ret;

    ret = bdrv_pread(bs->file, s->desc_offset, desc, DESC_SIZE);

    if (ret < 0) {

        return 0;

    }

    if (parent) {

        cid_str = "parentCID";

        cid_str_size = sizeof("parentCID");

    } else {

        cid_str = "CID";

        cid_str_size = sizeof("CID");

    }

    desc[DESC_SIZE - 1] = '\0';

    p_name = strstr(desc, cid_str);

    if (p_name != NULL) {

        p_name += cid_str_size;

        sscanf(p_name, "%x", &cid);

    }

    return cid;

}

static int vmdk_write_cid(BlockDriverState *bs, uint32_t cid)

{

    char desc[DESC_SIZE], tmp_desc[DESC_SIZE];

    char *p_name, *tmp_str;

    BDRVVmdkState *s = bs->opaque;

    int ret;

    ret = bdrv_pread(bs->file, s->desc_offset, desc, DESC_SIZE);

    if (ret < 0) {

        return ret;

    }

    desc[DESC_SIZE - 1] = '\0';

    tmp_str = strstr(desc, "parentCID");

    if (tmp_str == NULL) {

        return -EINVAL;

    }

    pstrcpy(tmp_desc, sizeof(tmp_desc), tmp_str);

    p_name = strstr(desc, "CID");

    if (p_name != NULL) {

        p_name += sizeof("CID");

        snprintf(p_name, sizeof(desc) - (p_name - desc), "%x\n", cid);

        pstrcat(desc, sizeof(desc), tmp_desc);

    }

    ret = bdrv_pwrite_sync(bs->file, s->desc_offset, desc, DESC_SIZE);

    if (ret < 0) {

        return ret;

    }

    return 0;

}

static int vmdk_is_cid_valid(BlockDriverState *bs)

{

#ifdef CHECK_CID

    BDRVVmdkState *s = bs->opaque;

    BlockDriverState *p_bs = bs->backing_hd;

    uint32_t cur_pcid;

    if (p_bs) {

        cur_pcid = vmdk_read_cid(p_bs, 0);

        if (s->parent_cid != cur_pcid) {

            /* CID not valid */

            return 0;

        }

    }

#endif

    /* CID valid */

    return 1;

}

/* Queue extents, if any, for reopen() */

static int vmdk_reopen_prepare(BDRVReopenState *state,

                               BlockReopenQueue *queue, Error **errp)

{

    BDRVVmdkState *s;

    int ret = -1;

    int i;

    VmdkExtent *e;

    assert(state != NULL);

    assert(state->bs != NULL);

    if (queue == NULL) {

        error_set(errp, ERROR_CLASS_GENERIC_ERROR,

                 "No reopen queue for VMDK extents");

        goto exit;

    }

    s = state->bs->opaque;

    assert(s != NULL);

    for (i = 0; i < s->num_extents; i++) {

        e = &s->extents[i];

        if (e->file != state->bs->file) {

            bdrv_reopen_queue(queue, e->file, state->flags);

        }

    }

    ret = 0;

exit:

    return ret;

}

static int vmdk_parent_open(BlockDriverState *bs)

{

    char *p_name;

    char desc[DESC_SIZE + 1];

    BDRVVmdkState *s = bs->opaque;

    int ret;

    desc[DESC_SIZE] = '\0';

    ret = bdrv_pread(bs->file, s->desc_offset, desc, DESC_SIZE);

    if (ret < 0) {

        return ret;

    }

    p_name = strstr(desc, "parentFileNameHint");

    if (p_name != NULL) {

        char *end_name;

        p_name += sizeof("parentFileNameHint") + 1;

        end_name = strchr(p_name, '\"');

        if (end_name == NULL) {

            return -EINVAL;

        }

        if ((end_name - p_name) > sizeof(bs->backing_file) - 1) {

            return -EINVAL;

        }

        pstrcpy(bs->backing_file, end_name - p_name + 1, p_name);

    }

    return 0;

}

/* Create and append extent to the extent array. Return the added VmdkExtent

 * address. return NULL if allocation failed. */

static VmdkExtent *vmdk_add_extent(BlockDriverState *bs,

                           BlockDriverState *file, bool flat, int64_t sectors,

                           int64_t l1_offset, int64_t l1_backup_offset,

                           uint32_t l1_size,

                           int l2_size, unsigned int cluster_sectors)

{

    VmdkExtent *extent;

    BDRVVmdkState *s = bs->opaque;

    s->extents = g_realloc(s->extents,

                              (s->num_extents + 1) * sizeof(VmdkExtent));

    extent = &s->extents[s->num_extents];

    s->num_extents++;

    memset(extent, 0, sizeof(VmdkExtent));

    extent->file = file;

    extent->flat = flat;

    extent->sectors = sectors;

    extent->l1_table_offset = l1_offset;

    extent->l1_backup_table_offset = l1_backup_offset;

    extent->l1_size = l1_size;

    extent->l1_entry_sectors = l2_size * cluster_sectors;

    extent->l2_size = l2_size;

    extent->cluster_sectors = cluster_sectors;

    if (s->num_extents > 1) {

        extent->end_sector = (*(extent - 1)).end_sector + extent->sectors;

    } else {

        extent->end_sector = extent->sectors;

    }

    bs->total_sectors = extent->end_sector;

    return extent;

}

static int vmdk_init_tables(BlockDriverState *bs, VmdkExtent *extent)

{

    int ret;

    int l1_size, i;

    /* read the L1 table */

    l1_size = extent->l1_size * sizeof(uint32_t);

    extent->l1_table = g_malloc(l1_size);

    ret = bdrv_pread(extent->file,

                    extent->l1_table_offset,

                    extent->l1_table,

                    l1_size);

    if (ret < 0) {

        goto fail_l1;

    }

    for (i = 0; i < extent->l1_size; i++) {

        le32_to_cpus(&extent->l1_table[i]);

    }

    if (extent->l1_backup_table_offset) {

        extent->l1_backup_table = g_malloc(l1_size);

        ret = bdrv_pread(extent->file,

                        extent->l1_backup_table_offset,

                        extent->l1_backup_table,

                        l1_size);

        if (ret < 0) {

            goto fail_l1b;

        }

        for (i = 0; i < extent->l1_size; i++) {

            le32_to_cpus(&extent->l1_backup_table[i]);

        }

    }

    extent->l2_cache =

        g_malloc(extent->l2_size * L2_CACHE_SIZE * sizeof(uint32_t));

    return 0;

 fail_l1b:

    g_free(extent->l1_backup_table);

 fail_l1:

    g_free(extent->l1_table);

    return ret;

}

static int vmdk_open_vmdk3(BlockDriverState *bs,

                           BlockDriverState *file,

                           int flags)

{

    int ret;

    uint32_t magic;

    VMDK3Header header;

    VmdkExtent *extent;

    ret = bdrv_pread(file, sizeof(magic), &header, sizeof(header));

    if (ret < 0) {

        return ret;

    }

    extent = vmdk_add_extent(bs,

                             bs->file, false,

                             le32_to_cpu(header.disk_sectors),

                             le32_to_cpu(header.l1dir_offset) << 9,

                             0, 1 << 6, 1 << 9,

                             le32_to_cpu(header.granularity));

    ret = vmdk_init_tables(bs, extent);

    if (ret) {

        /* free extent allocated by vmdk_add_extent */

        vmdk_free_last_extent(bs);

    }

    return ret;

}

static int vmdk_open_desc_file(BlockDriverState *bs, int flags,

                               int64_t desc_offset);

static int vmdk_open_vmdk4(BlockDriverState *bs,

                           BlockDriverState *file,

                           int flags)

{

    int ret;

    uint32_t magic;

    uint32_t l1_size, l1_entry_sectors;

    VMDK4Header header;

    VmdkExtent *extent;

    int64_t l1_backup_offset = 0;

    ret = bdrv_pread(file, sizeof(magic), &header, sizeof(header));

    if (ret < 0) {

        return ret;

    }

    if (header.capacity == 0 && header.desc_offset) {

        return vmdk_open_desc_file(bs, flags, header.desc_offset << 9);

    }

    if (le64_to_cpu(header.gd_offset) == VMDK4_GD_AT_END) {

        /*

         * The footer takes precedence over the header, so read it in. The

         * footer starts at offset -1024 from the end: One sector for the

         * footer, and another one for the end-of-stream marker.

         */

        struct {

            struct {

                uint64_t val;

                uint32_t size;

                uint32_t type;

                uint8_t pad[512 - 16];

            } QEMU_PACKED footer_marker;

            uint32_t magic;

            VMDK4Header header;

            uint8_t pad[512 - 4 - sizeof(VMDK4Header)];

            struct {

                uint64_t val;

                uint32_t size;

                uint32_t type;

                uint8_t pad[512 - 16];

            } QEMU_PACKED eos_marker;

        } QEMU_PACKED footer;

        ret = bdrv_pread(file,

            bs->file->total_sectors * 512 - 1536,

            &footer, sizeof(footer));

        if (ret < 0) {

            return ret;

        }

        /* Some sanity checks for the footer */

        if (be32_to_cpu(footer.magic) != VMDK4_MAGIC ||

            le32_to_cpu(footer.footer_marker.size) != 0  ||

            le32_to_cpu(footer.footer_marker.type) != MARKER_FOOTER ||

            le64_to_cpu(footer.eos_marker.val) != 0  ||

            le32_to_cpu(footer.eos_marker.size) != 0  ||

            le32_to_cpu(footer.eos_marker.type) != MARKER_END_OF_STREAM)

        {

            return -EINVAL;

        }

        header = footer.header;

    }

    l1_entry_sectors = le32_to_cpu(header.num_gtes_per_gte)

                        * le64_to_cpu(header.granularity);

    if (l1_entry_sectors == 0) {

        return -EINVAL;

    }

    l1_size = (le64_to_cpu(header.capacity) + l1_entry_sectors - 1)

                / l1_entry_sectors;

    if (le32_to_cpu(header.flags) & VMDK4_FLAG_RGD) {

        l1_backup_offset = le64_to_cpu(header.rgd_offset) << 9;

    }

    extent = vmdk_add_extent(bs, file, false,

                          le64_to_cpu(header.capacity),

                          le64_to_cpu(header.gd_offset) << 9,

                          l1_backup_offset,

                          l1_size,

                          le32_to_cpu(header.num_gtes_per_gte),

                          le64_to_cpu(header.granularity));

    extent->compressed =

        le16_to_cpu(header.compressAlgorithm) == VMDK4_COMPRESSION_DEFLATE;

    extent->has_marker = le32_to_cpu(header.flags) & VMDK4_FLAG_MARKER;

    ret = vmdk_init_tables(bs, extent);

    if (ret) {

        /* free extent allocated by vmdk_add_extent */

        vmdk_free_last_extent(bs);

    }

    return ret;

}

/* find an option value out of descriptor file */

static int vmdk_parse_description(const char *desc, const char *opt_name,

        char *buf, int buf_size)

{

    char *opt_pos, *opt_end;

    const char *end = desc + strlen(desc);

    opt_pos = strstr(desc, opt_name);

    if (!opt_pos) {

        return -1;

    }

    /* Skip "=\"" following opt_name */

    opt_pos += strlen(opt_name) + 2;

    if (opt_pos >= end) {

        return -1;

    }

    opt_end = opt_pos;

    while (opt_end < end && *opt_end != '"') {

        opt_end++;

    }

    if (opt_end == end || buf_size < opt_end - opt_pos + 1) {

        return -1;

    }

    pstrcpy(buf, opt_end - opt_pos + 1, opt_pos);

    return 0;

}

/* Open an extent file and append to bs array */

static int vmdk_open_sparse(BlockDriverState *bs,

                            BlockDriverState *file,

                            int flags)

{

    uint32_t magic;

    if (bdrv_pread(file, 0, &magic, sizeof(magic)) != sizeof(magic)) {

        return -EIO;

    }

    magic = be32_to_cpu(magic);

    switch (magic) {

        case VMDK3_MAGIC:

            return vmdk_open_vmdk3(bs, file, flags);

            break;

        case VMDK4_MAGIC:

            return vmdk_open_vmdk4(bs, file, flags);

            break;

        default:

            return -EINVAL;

            break;

    }

}

static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,

        const char *desc_file_path)

{

    int ret;

    char access[11];

    char type[11];

    char fname[512];

    const char *p = desc;

    int64_t sectors = 0;

    int64_t flat_offset;

    char extent_path[PATH_MAX];

    BlockDriverState *extent_file;

    while (*p) {

        /* parse extent line:

         * RW [size in sectors] FLAT "file-name.vmdk" OFFSET

         * or

         * RW [size in sectors] SPARSE "file-name.vmdk"

         */

        flat_offset = -1;

        ret = sscanf(p, "%10s %" SCNd64 " %10s %511s %" SCNd64,

                access, &sectors, type, fname, &flat_offset);

        if (ret < 4 || strcmp(access, "RW")) {

            goto next_line;

        } else if (!strcmp(type, "FLAT")) {

            if (ret != 5 || flat_offset < 0) {

                return -EINVAL;

            }

        } else if (ret != 4) {

            return -EINVAL;

        }

        /* trim the quotation marks around */

        if (fname[0] == '"') {

            memmove(fname, fname + 1, strlen(fname));

            if (strlen(fname) <= 1 || fname[strlen(fname) - 1] != '"') {

                return -EINVAL;

            }

            fname[strlen(fname) - 1] = '\0';

        }

        if (sectors <= 0 ||

            (strcmp(type, "FLAT") && strcmp(type, "SPARSE")) ||

            (strcmp(access, "RW"))) {

            goto next_line;

        }

        path_combine(extent_path, sizeof(extent_path),

                desc_file_path, fname);

        ret = bdrv_file_open(&extent_file, extent_path, bs->open_flags);

        if (ret) {

            return ret;

        }

        /* save to extents array */

        if (!strcmp(type, "FLAT")) {

            /* FLAT extent */

            VmdkExtent *extent;

            extent = vmdk_add_extent(bs, extent_file, true, sectors,

                            0, 0, 0, 0, sectors);

            extent->flat_start_offset = flat_offset << 9;

        } else if (!strcmp(type, "SPARSE")) {

            /* SPARSE extent */

            ret = vmdk_open_sparse(bs, extent_file, bs->open_flags);

            if (ret) {

                bdrv_delete(extent_file);

                return ret;

            }

        } else {

            fprintf(stderr,

                "VMDK: Not supported extent type \"%s\""".\n", type);

            return -ENOTSUP;

        }

next_line:

        /* move to next line */

        while (*p && *p != '\n') {

            p++;

        }

        p++;

    }

    return 0;

}

static int vmdk_open_desc_file(BlockDriverState *bs, int flags,

                               int64_t desc_offset)

{

    int ret;

    char buf[2048];

    char ct[128];

    BDRVVmdkState *s = bs->opaque;

    ret = bdrv_pread(bs->file, desc_offset, buf, sizeof(buf));

    if (ret < 0) {

        return ret;

    }

    buf[2047] = '\0';

    if (vmdk_parse_description(buf, "createType", ct, sizeof(ct))) {

        return -EINVAL;

    }

    if (strcmp(ct, "monolithicFlat") &&

        strcmp(ct, "twoGbMaxExtentSparse") &&

        strcmp(ct, "twoGbMaxExtentFlat")) {

        fprintf(stderr,

                "VMDK: Not supported image type \"%s\""".\n", ct);

        return -ENOTSUP;

    }

    s->desc_offset = 0;

    return vmdk_parse_extents(buf, bs, bs->file->filename);

}

static int vmdk_open(BlockDriverState *bs, int flags)

{

    int ret;

    BDRVVmdkState *s = bs->opaque;

    if (vmdk_open_sparse(bs, bs->file, flags) == 0) {

        s->desc_offset = 0x200;

    } else {

        ret = vmdk_open_desc_file(bs, flags, 0);

        if (ret) {

            goto fail;

        }

    }

    /* try to open parent images, if exist */

    ret = vmdk_parent_open(bs);

    if (ret) {

        goto fail;

    }

    s->parent_cid = vmdk_read_cid(bs, 1);

    qemu_co_mutex_init(&s->lock);

    /* Disable migration when VMDK images are used */

    error_set(&s->migration_blocker,

              QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,

              "vmdk", bs->device_name, "live migration");

    migrate_add_blocker(s->migration_blocker);

    return 0;

fail:

    vmdk_free_extents(bs);

    return ret;

}

static int get_whole_cluster(BlockDriverState *bs,

                VmdkExtent *extent,

                uint64_t cluster_offset,

                uint64_t offset,

                bool allocate)

{

    /* 128 sectors * 512 bytes each = grain size 64KB */

    uint8_t  whole_grain[extent->cluster_sectors * 512];

    /* we will be here if it's first write on non-exist grain(cluster).

     * try to read from parent image, if exist */

    if (bs->backing_hd) {

        int ret;

        if (!vmdk_is_cid_valid(bs)) {

            return -1;

        }

        /* floor offset to cluster */

        offset -= offset % (extent->cluster_sectors * 512);

        ret = bdrv_read(bs->backing_hd, offset >> 9, whole_grain,

                extent->cluster_sectors);

        if (ret < 0) {

            return -1;

        }

        /* Write grain only into the active image */

        ret = bdrv_write(extent->file, cluster_offset, whole_grain,

                extent->cluster_sectors);

        if (ret < 0) {

            return -1;

        }

    }

    return 0;

}

static int vmdk_L2update(VmdkExtent *extent, VmdkMetaData *m_data)

{

    /* update L2 table */

    if (bdrv_pwrite_sync(

                extent->file,

                ((int64_t)m_data->l2_offset * 512)

                    + (m_data->l2_index * sizeof(m_data->offset)),

                &(m_data->offset),

                sizeof(m_data->offset)

            ) < 0) {

        return -1;

    }

    /* update backup L2 table */

    if (extent->l1_backup_table_offset != 0) {

        m_data->l2_offset = extent->l1_backup_table[m_data->l1_index];

        if (bdrv_pwrite_sync(

                    extent->file,

                    ((int64_t)m_data->l2_offset * 512)

                        + (m_data->l2_index * sizeof(m_data->offset)),

                    &(m_data->offset), sizeof(m_data->offset)

                ) < 0) {

            return -1;

        }

    }

    return 0;

}

static int get_cluster_offset(BlockDriverState *bs,

                                    VmdkExtent *extent,

                                    VmdkMetaData *m_data,

                                    uint64_t offset,

                                    int allocate,

                                    uint64_t *cluster_offset)

{

    unsigned int l1_index, l2_offset, l2_index;

    int min_index, i, j;

    uint32_t min_count, *l2_table, tmp = 0;

    if (m_data) {

        m_data->valid = 0;

    }

    if (extent->flat) {

        *cluster_offset = extent->flat_start_offset;

        return 0;

    }

    offset -= (extent->end_sector - extent->sectors) * SECTOR_SIZE;

    l1_index = (offset >> 9) / extent->l1_entry_sectors;

    if (l1_index >= extent->l1_size) {

        return -1;

    }

    l2_offset = extent->l1_table[l1_index];

    if (!l2_offset) {

        return -1;

    }

    for (i = 0; i < L2_CACHE_SIZE; i++) {

        if (l2_offset == extent->l2_cache_offsets[i]) {

            /* increment the hit count */

            if (++extent->l2_cache_counts[i] == 0xffffffff) {

                for (j = 0; j < L2_CACHE_SIZE; j++) {

                    extent->l2_cache_counts[j] >>= 1;

                }

            }

            l2_table = extent->l2_cache + (i * extent->l2_size);

            goto found;

        }

    }

    /* not found: load a new entry in the least used one */

    min_index = 0;

    min_count = 0xffffffff;

    for (i = 0; i < L2_CACHE_SIZE; i++) {

        if (extent->l2_cache_counts[i] < min_count) {

            min_count = extent->l2_cache_counts[i];

            min_index = i;

        }

    }

    l2_table = extent->l2_cache + (min_index * extent->l2_size);

    if (bdrv_pread(

                extent->file,

                (int64_t)l2_offset * 512,

                l2_table,

                extent->l2_size * sizeof(uint32_t)