Archipelago » qemu

/*

 * 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 "block/qcow2.h"

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;

void qcow2_free_snapshots(BlockDriverState *bs)

{

    BDRVQcowState *s = bs->opaque;

    int i;

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

        g_free(s->snapshots[i].name);

        g_free(s->snapshots[i].id_str);

    }

    g_free(s->snapshots);

    s->snapshots = NULL;

    s->nb_snapshots = 0;

}

int qcow2_read_snapshots(BlockDriverState *bs)

{

    BDRVQcowState *s = bs->opaque;

    QCowSnapshotHeader h;

    QCowSnapshot *sn;

    int i, id_str_size, name_size;

    int64_t offset;

    uint32_t extra_data_size;

    int ret;

    if (!s->nb_snapshots) {

        s->snapshots = NULL;

        s->snapshots_size = 0;

        return 0;

    }

    offset = s->snapshots_offset;

    s->snapshots = g_malloc0(s->nb_snapshots * sizeof(QCowSnapshot));

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

        /* Read statically sized part of the snapshot header */

        offset = align_offset(offset, 8);

        ret = bdrv_pread(bs->file, offset, &h, sizeof(h));

        if (ret < 0) {

            goto fail;

        }

        offset += sizeof(h);

        sn = s->snapshots + i;

        sn->l1_table_offset = be64_to_cpu(h.l1_table_offset);

        sn->l1_size = be32_to_cpu(h.l1_size);

        sn->vm_state_size = be32_to_cpu(h.vm_state_size);

        sn->date_sec = be32_to_cpu(h.date_sec);

        sn->date_nsec = be32_to_cpu(h.date_nsec);

        sn->vm_clock_nsec = be64_to_cpu(h.vm_clock_nsec);

        extra_data_size = be32_to_cpu(h.extra_data_size);

        id_str_size = be16_to_cpu(h.id_str_size);

        name_size = be16_to_cpu(h.name_size);

        /* Skip extra data */

        offset += extra_data_size;

        /* Read snapshot ID */

        sn->id_str = g_malloc(id_str_size + 1);

        ret = bdrv_pread(bs->file, offset, sn->id_str, id_str_size);

        if (ret < 0) {

            goto fail;

        }

        offset += id_str_size;

        sn->id_str[id_str_size] = '\0';

        /* Read snapshot name */

        sn->name = g_malloc(name_size + 1);

        ret = bdrv_pread(bs->file, offset, sn->name, name_size);

        if (ret < 0) {

            goto fail;

        }

        offset += name_size;

        sn->name[name_size] = '\0';

    }

    s->snapshots_size = offset - s->snapshots_offset;

    return 0;

fail:

    qcow2_free_snapshots(bs);

    return ret;

}

/* add at the end of the file a new list of snapshots */

static int qcow2_write_snapshots(BlockDriverState *bs)

{

    BDRVQcowState *s = bs->opaque;

    QCowSnapshot *sn;

    QCowSnapshotHeader h;

    int i, name_size, id_str_size, snapshots_size;

    struct {

        uint32_t nb_snapshots;

        uint64_t snapshots_offset;

    } QEMU_PACKED header_data;

    int64_t offset, snapshots_offset;

    int ret;

    /* compute the size of the snapshots */

    offset = 0;

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

        sn = s->snapshots + i;

        offset = align_offset(offset, 8);

        offset += sizeof(h);

        offset += strlen(sn->id_str);

        offset += strlen(sn->name);

    }

    snapshots_size = offset;

    /* Allocate space for the new snapshot list */

    snapshots_offset = qcow2_alloc_clusters(bs, snapshots_size);

    bdrv_flush(bs->file);

    offset = snapshots_offset;

    if (offset < 0) {

        return offset;

    }

    /* Write all snapshots to the new list */

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

        sn = s->snapshots + i;

        memset(&h, 0, sizeof(h));

        h.l1_table_offset = cpu_to_be64(sn->l1_table_offset);

        h.l1_size = cpu_to_be32(sn->l1_size);

        h.vm_state_size = cpu_to_be32(sn->vm_state_size);

        h.date_sec = cpu_to_be32(sn->date_sec);

        h.date_nsec = cpu_to_be32(sn->date_nsec);

        h.vm_clock_nsec = cpu_to_be64(sn->vm_clock_nsec);

        id_str_size = strlen(sn->id_str);

        name_size = strlen(sn->name);

        h.id_str_size = cpu_to_be16(id_str_size);

        h.name_size = cpu_to_be16(name_size);

        offset = align_offset(offset, 8);

        ret = bdrv_pwrite(bs->file, offset, &h, sizeof(h));

        if (ret < 0) {

            goto fail;

        }

        offset += sizeof(h);

        ret = bdrv_pwrite(bs->file, offset, sn->id_str, id_str_size);

        if (ret < 0) {

            goto fail;

        }

        offset += id_str_size;

        ret = bdrv_pwrite(bs->file, offset, sn->name, name_size);

        if (ret < 0) {

            goto fail;

        }

        offset += name_size;

    }

    /*

     * Update the header to point to the new snapshot table. This requires the

     * new table and its refcounts to be stable on disk.

     */

    ret = bdrv_flush(bs);

    if (ret < 0) {

        goto fail;

    }

    QEMU_BUILD_BUG_ON(offsetof(QCowHeader, snapshots_offset) !=

        offsetof(QCowHeader, nb_snapshots) + sizeof(header_data.nb_snapshots));

    header_data.nb_snapshots        = cpu_to_be32(s->nb_snapshots);

    header_data.snapshots_offset    = cpu_to_be64(snapshots_offset);

    ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, nb_snapshots),

                           &header_data, sizeof(header_data));

    if (ret < 0) {

        goto fail;

    }

    /* free the old snapshot table */

    qcow2_free_clusters(bs, s->snapshots_offset, s->snapshots_size);

    s->snapshots_offset = snapshots_offset;

    s->snapshots_size = snapshots_size;

    return 0;

fail:

    return ret;

}

static void find_new_snapshot_id(BlockDriverState *bs,

                                 char *id_str, int id_str_size)

{

    BDRVQcowState *s = bs->opaque;

    QCowSnapshot *sn;

    int i, id, id_max = 0;

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

        sn = s->snapshots + i;

        id = strtoul(sn->id_str, NULL, 10);

        if (id > id_max)

            id_max = id;

    }

    snprintf(id_str, id_str_size, "%d", id_max + 1);

}

static int find_snapshot_by_id(BlockDriverState *bs, const char *id_str)

{

    BDRVQcowState *s = bs->opaque;

    int i;

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

        if (!strcmp(s->snapshots[i].id_str, id_str))

            return i;

    }

    return -1;

}

static int find_snapshot_by_id_or_name(BlockDriverState *bs, const char *name)

{

    BDRVQcowState *s = bs->opaque;

    int i, ret;

    ret = find_snapshot_by_id(bs, name);

    if (ret >= 0)

        return ret;

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

        if (!strcmp(s->snapshots[i].name, name))

            return i;

    }

    return -1;

}

/* if no id is provided, a new one is constructed */

int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)

{

    BDRVQcowState *s = bs->opaque;

    QCowSnapshot *new_snapshot_list = NULL;

    QCowSnapshot *old_snapshot_list = NULL;

    QCowSnapshot sn1, *sn = &sn1;

    int i, ret;

    uint64_t *l1_table = NULL;

    int64_t l1_table_offset;

    memset(sn, 0, sizeof(*sn));

    /* Generate an ID if it wasn't passed */

    if (sn_info->id_str[0] == '\0') {

        find_new_snapshot_id(bs, sn_info->id_str, sizeof(sn_info->id_str));

    }

    /* Check that the ID is unique */

    if (find_snapshot_by_id(bs, sn_info->id_str) >= 0) {

        return -ENOENT;

    }

    /* Populate sn with passed data */

    sn->id_str = g_strdup(sn_info->id_str);

    sn->name = g_strdup(sn_info->name);

    sn->vm_state_size = sn_info->vm_state_size;

    sn->date_sec = sn_info->date_sec;

    sn->date_nsec = sn_info->date_nsec;

    sn->vm_clock_nsec = sn_info->vm_clock_nsec;

    /* Allocate the L1 table of the snapshot and copy the current one there. */

    l1_table_offset = qcow2_alloc_clusters(bs, s->l1_size * sizeof(uint64_t));

    if (l1_table_offset < 0) {

        ret = l1_table_offset;

        goto fail;

    }

    sn->l1_table_offset = l1_table_offset;

    sn->l1_size = s->l1_size;

    l1_table = g_malloc(s->l1_size * sizeof(uint64_t));

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

        l1_table[i] = cpu_to_be64(s->l1_table[i]);

    }

    ret = bdrv_pwrite(bs->file, sn->l1_table_offset, l1_table,

                      s->l1_size * sizeof(uint64_t));

    if (ret < 0) {

        goto fail;

    }

    g_free(l1_table);

    l1_table = NULL;

    /*

     * Increase the refcounts of all clusters and make sure everything is

     * stable on disk before updating the snapshot table to contain a pointer

     * to the new L1 table.

     */

    ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1);

    if (ret < 0) {

        goto fail;

    }

    ret = bdrv_flush(bs);

    if (ret < 0) {

        goto fail;

    }

    /* Append the new snapshot to the snapshot list */

    new_snapshot_list = g_malloc((s->nb_snapshots + 1) * sizeof(QCowSnapshot));

    if (s->snapshots) {

        memcpy(new_snapshot_list, s->snapshots,

               s->nb_snapshots * sizeof(QCowSnapshot));

        old_snapshot_list = s->snapshots;

    }

    s->snapshots = new_snapshot_list;

    s->snapshots[s->nb_snapshots++] = *sn;

    ret = qcow2_write_snapshots(bs);

    if (ret < 0) {

        g_free(s->snapshots);

        s->snapshots = old_snapshot_list;

        goto fail;

    }

    g_free(old_snapshot_list);

#ifdef DEBUG_ALLOC

    {

      BdrvCheckResult result = {0};

      qcow2_check_refcounts(bs, &result);

    }

#endif

    return 0;

fail:

    g_free(sn->id_str);

    g_free(sn->name);

    g_free(l1_table);

    return ret;

}

/* copy the snapshot 'snapshot_name' into the current disk image */

int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)

{

    BDRVQcowState *s = bs->opaque;

    QCowSnapshot *sn;

    int i, snapshot_index;

    int cur_l1_bytes, sn_l1_bytes;

    int ret;

    uint64_t *sn_l1_table = NULL;

    /* Search the snapshot */

    snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);

    if (snapshot_index < 0) {

        return -ENOENT;

    }

    sn = &s->snapshots[snapshot_index];

    /*

     * Make sure that the current L1 table is big enough to contain the whole

     * L1 table of the snapshot. If the snapshot L1 table is smaller, the

     * current one must be padded with zeros.

     */

    ret = qcow2_grow_l1_table(bs, sn->l1_size, true);

    if (ret < 0) {

        goto fail;

    }

    cur_l1_bytes = s->l1_size * sizeof(uint64_t);

    sn_l1_bytes = sn->l1_size * sizeof(uint64_t);

    /*

     * Copy the snapshot L1 table to the current L1 table.

     *

     * Before overwriting the old current L1 table on disk, make sure to

     * increase all refcounts for the clusters referenced by the new one.

     * Decrease the refcount referenced by the old one only when the L1

     * table is overwritten.

     */

    sn_l1_table = g_malloc0(cur_l1_bytes);

    ret = bdrv_pread(bs->file, sn->l1_table_offset, sn_l1_table, sn_l1_bytes);

    if (ret < 0) {

        goto fail;

    }

    ret = qcow2_update_snapshot_refcount(bs, sn->l1_table_offset,

                                         sn->l1_size, 1);

    if (ret < 0) {

        goto fail;

    }

    ret = bdrv_pwrite_sync(bs->file, s->l1_table_offset, sn_l1_table,

                           cur_l1_bytes);

    if (ret < 0) {

        goto fail;

    }

    /*

     * Decrease refcount of clusters of current L1 table.

     *

     * At this point, the in-memory s->l1_table points to the old L1 table,

     * whereas on disk we already have the new one.

     *

     * qcow2_update_snapshot_refcount special cases the current L1 table to use

     * the in-memory data instead of really using the offset to load a new one,

     * which is why this works.

     */

    ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset,

                                         s->l1_size, -1);

    /*

     * Now update the in-memory L1 table to be in sync with the on-disk one. We

     * need to do this even if updating refcounts failed.

     */

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

        s->l1_table[i] = be64_to_cpu(sn_l1_table[i]);

    }

    if (ret < 0) {

        goto fail;

    }

    g_free(sn_l1_table);

    sn_l1_table = NULL;

    /*

     * Update QCOW_OFLAG_COPIED in the active L1 table (it may have changed

     * when we decreased the refcount of the old snapshot.

     */

    ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);

    if (ret < 0) {

        goto fail;

    }

#ifdef DEBUG_ALLOC

    {

        BdrvCheckResult result = {0};

        qcow2_check_refcounts(bs, &result);

    }

#endif

    return 0;

fail:

    g_free(sn_l1_table);

    return ret;

}

int qcow2_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)

{

    BDRVQcowState *s = bs->opaque;

    QCowSnapshot sn;

    int snapshot_index, ret;

    /* Search the snapshot */

    snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);

    if (snapshot_index < 0) {

        return -ENOENT;

    }

    sn = s->snapshots[snapshot_index];

    /* Remove it from the snapshot list */

    memmove(s->snapshots + snapshot_index,

            s->snapshots + snapshot_index + 1,

            (s->nb_snapshots - snapshot_index - 1) * sizeof(sn));

    s->nb_snapshots--;

    ret = qcow2_write_snapshots(bs);

    if (ret < 0) {

        return ret;

    }

    /*

     * The snapshot is now unused, clean up. If we fail after this point, we

     * won't recover but just leak clusters.

     */

    g_free(sn.id_str);

    g_free(sn.name);

    /*

     * Now decrease the refcounts of clusters referenced by the snapshot and

     * free the L1 table.

     */

    ret = qcow2_update_snapshot_refcount(bs, sn.l1_table_offset,

                                         sn.l1_size, -1);

    if (ret < 0) {

        return ret;

    }

    qcow2_free_clusters(bs, sn.l1_table_offset, sn.l1_size * sizeof(uint64_t));

    /* must update the copied flag on the current cluster offsets */

    ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);

    if (ret < 0) {

        return ret;

    }

#ifdef DEBUG_ALLOC

    {

        BdrvCheckResult result = {0};

        qcow2_check_refcounts(bs, &result);

    }

#endif

    return 0;

}

int qcow2_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)

{

    BDRVQcowState *s = bs->opaque;

    QEMUSnapshotInfo *sn_tab, *sn_info;

    QCowSnapshot *sn;

    int i;

    if (!s->nb_snapshots) {

        *psn_tab = NULL;

        return s->nb_snapshots;

    }

    sn_tab = g_malloc0(s->nb_snapshots * sizeof(QEMUSnapshotInfo));

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

        sn_info = sn_tab + i;

        sn = s->snapshots + i;

        pstrcpy(sn_info->id_str, sizeof(sn_info->id_str),

                sn->id_str);

        pstrcpy(sn_info->name, sizeof(sn_info->name),

                sn->name);

        sn_info->vm_state_size = sn->vm_state_size;

        sn_info->date_sec = sn->date_sec;

        sn_info->date_nsec = sn->date_nsec;

        sn_info->vm_clock_nsec = sn->vm_clock_nsec;

    }

    *psn_tab = sn_tab;

    return s->nb_snapshots;

}

int qcow2_snapshot_load_tmp(BlockDriverState *bs, const char *snapshot_name)

{

    int i, snapshot_index;

    BDRVQcowState *s = bs->opaque;

    QCowSnapshot *sn;

    uint64_t *new_l1_table;

    int new_l1_bytes;

    int ret;

    assert(bs->read_only);

    /* Search the snapshot */

    snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_name);

    if (snapshot_index < 0) {

        return -ENOENT;

    }

    sn = &s->snapshots[snapshot_index];

    /* Allocate and read in the snapshot's L1 table */

    new_l1_bytes = s->l1_size * sizeof(uint64_t);

    new_l1_table = g_malloc0(align_offset(new_l1_bytes, 512));

    ret = bdrv_pread(bs->file, sn->l1_table_offset, new_l1_table, new_l1_bytes);

    if (ret < 0) {

        g_free(new_l1_table);

        return ret;

    }

    /* Switch the L1 table */

    g_free(s->l1_table);

    s->l1_size = sn->l1_size;

    s->l1_table_offset = sn->l1_table_offset;

    s->l1_table = new_l1_table;

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

        be64_to_cpus(&s->l1_table[i]);

    }

    return 0;

}