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"

static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size);

static int update_refcount(BlockDriverState *bs,

                            int64_t offset, int64_t length,

                            int addend);

static int cache_refcount_updates = 0;

static int write_refcount_block(BDRVQcowState *s)

{

    size_t size = s->cluster_size;

    if (s->refcount_block_cache_offset == 0) {

        return 0;

    }

    if (bdrv_pwrite(s->hd, s->refcount_block_cache_offset,

            s->refcount_block_cache, size) != size)

    {

        return -EIO;

    }

    return 0;

}

/*********************************************************/

/* refcount handling */

int qcow2_refcount_init(BlockDriverState *bs)

{

    BDRVQcowState *s = bs->opaque;

    int ret, refcount_table_size2, i;

    s->refcount_block_cache = qemu_malloc(s->cluster_size);

    refcount_table_size2 = s->refcount_table_size * sizeof(uint64_t);

    s->refcount_table = qemu_malloc(refcount_table_size2);

    if (s->refcount_table_size > 0) {

        ret = bdrv_pread(s->hd, s->refcount_table_offset,

                         s->refcount_table, refcount_table_size2);

        if (ret != refcount_table_size2)

            goto fail;

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

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

    }

    return 0;

 fail:

    return -ENOMEM;

}

void qcow2_refcount_close(BlockDriverState *bs)

{

    BDRVQcowState *s = bs->opaque;

    qemu_free(s->refcount_block_cache);

    qemu_free(s->refcount_table);

}

static int load_refcount_block(BlockDriverState *bs,

                               int64_t refcount_block_offset)

{

    BDRVQcowState *s = bs->opaque;

    int ret;

    if (cache_refcount_updates) {

        write_refcount_block(s);

    }

    ret = bdrv_pread(s->hd, refcount_block_offset, s->refcount_block_cache,

                     s->cluster_size);

    if (ret != s->cluster_size)

        return -EIO;

    s->refcount_block_cache_offset = refcount_block_offset;

    return 0;

}

static int get_refcount(BlockDriverState *bs, int64_t cluster_index)

{

    BDRVQcowState *s = bs->opaque;

    int refcount_table_index, block_index;

    int64_t refcount_block_offset;

    refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);

    if (refcount_table_index >= s->refcount_table_size)

        return 0;

    refcount_block_offset = s->refcount_table[refcount_table_index];

    if (!refcount_block_offset)

        return 0;

    if (refcount_block_offset != s->refcount_block_cache_offset) {

        /* better than nothing: return allocated if read error */

        if (load_refcount_block(bs, refcount_block_offset) < 0)

            return 1;

    }

    block_index = cluster_index &

        ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);

    return be16_to_cpu(s->refcount_block_cache[block_index]);

}

static int grow_refcount_table(BlockDriverState *bs, int min_size)

{

    BDRVQcowState *s = bs->opaque;

    int new_table_size, new_table_size2, refcount_table_clusters, i, ret;

    uint64_t *new_table;

    int64_t table_offset;

    uint8_t data[12];

    int old_table_size;

    int64_t old_table_offset;

    if (min_size <= s->refcount_table_size)

        return 0;

    /* compute new table size */

    refcount_table_clusters = s->refcount_table_size >> (s->cluster_bits - 3);

    for(;;) {

        if (refcount_table_clusters == 0) {

            refcount_table_clusters = 1;

        } else {

            refcount_table_clusters = (refcount_table_clusters * 3 + 1) / 2;

        }

        new_table_size = refcount_table_clusters << (s->cluster_bits - 3);

        if (min_size <= new_table_size)

            break;

    }

#ifdef DEBUG_ALLOC2

    printf("grow_refcount_table from %d to %d\n",

           s->refcount_table_size,

           new_table_size);

#endif

    new_table_size2 = new_table_size * sizeof(uint64_t);

    new_table = qemu_mallocz(new_table_size2);

    memcpy(new_table, s->refcount_table,

           s->refcount_table_size * sizeof(uint64_t));

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

        cpu_to_be64s(&new_table[i]);

    /* Note: we cannot update the refcount now to avoid recursion */

    table_offset = alloc_clusters_noref(bs, new_table_size2);

    ret = bdrv_pwrite(s->hd, table_offset, new_table, new_table_size2);

    if (ret != new_table_size2)

        goto fail;

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

        be64_to_cpus(&new_table[i]);

    cpu_to_be64w((uint64_t*)data, table_offset);

    cpu_to_be32w((uint32_t*)(data + 8), refcount_table_clusters);

    ret = bdrv_pwrite(s->hd, offsetof(QCowHeader, refcount_table_offset),

                    data, sizeof(data));

    if (ret != sizeof(data)) {

        goto fail;

    }

    qemu_free(s->refcount_table);

    old_table_offset = s->refcount_table_offset;

    old_table_size = s->refcount_table_size;

    s->refcount_table = new_table;

    s->refcount_table_size = new_table_size;

    s->refcount_table_offset = table_offset;

    update_refcount(bs, table_offset, new_table_size2, 1);

    qcow2_free_clusters(bs, old_table_offset, old_table_size * sizeof(uint64_t));

    return 0;

 fail:

    qemu_free(new_table);

    return ret < 0 ? ret : -EIO;

}

static int64_t alloc_refcount_block(BlockDriverState *bs, int64_t cluster_index)

{

    BDRVQcowState *s = bs->opaque;

    int64_t offset, refcount_block_offset;

    unsigned int refcount_table_index;

    int ret;

    uint64_t data64;

    int cache = cache_refcount_updates;

    /* Find L1 index and grow refcount table if needed */

    refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);

    if (refcount_table_index >= s->refcount_table_size) {

        ret = grow_refcount_table(bs, refcount_table_index + 1);

        if (ret < 0)

            return ret;

    }

    /* Load or allocate the refcount block */

    refcount_block_offset = s->refcount_table[refcount_table_index];

    if (!refcount_block_offset) {

        if (cache_refcount_updates) {

            write_refcount_block(s);

            cache_refcount_updates = 0;

        }

        /* create a new refcount block */

        /* Note: we cannot update the refcount now to avoid recursion */

        offset = alloc_clusters_noref(bs, s->cluster_size);

        memset(s->refcount_block_cache, 0, s->cluster_size);

        ret = bdrv_pwrite(s->hd, offset, s->refcount_block_cache, s->cluster_size);

        if (ret != s->cluster_size)

            return -EINVAL;

        s->refcount_table[refcount_table_index] = offset;

        data64 = cpu_to_be64(offset);

        ret = bdrv_pwrite(s->hd, s->refcount_table_offset +

                          refcount_table_index * sizeof(uint64_t),

                          &data64, sizeof(data64));

        if (ret != sizeof(data64))

            return -EINVAL;

        refcount_block_offset = offset;

        s->refcount_block_cache_offset = offset;

        update_refcount(bs, offset, s->cluster_size, 1);

        cache_refcount_updates = cache;

    } else {

        if (refcount_block_offset != s->refcount_block_cache_offset) {

            if (load_refcount_block(bs, refcount_block_offset) < 0)

                return -EIO;

        }

    }

    return refcount_block_offset;

}

#define REFCOUNTS_PER_SECTOR (512 >> REFCOUNT_SHIFT)

static int write_refcount_block_entries(BDRVQcowState *s,

    int64_t refcount_block_offset, int first_index, int last_index)

{

    size_t size;

    if (cache_refcount_updates) {

        return 0;

    }

    first_index &= ~(REFCOUNTS_PER_SECTOR - 1);

    last_index = (last_index + REFCOUNTS_PER_SECTOR)

        & ~(REFCOUNTS_PER_SECTOR - 1);

    size = (last_index - first_index) << REFCOUNT_SHIFT;

    if (bdrv_pwrite(s->hd,

        refcount_block_offset + (first_index << REFCOUNT_SHIFT),

        &s->refcount_block_cache[first_index], size) != size)

    {

        return -EIO;

    }

    return 0;

}

/* XXX: cache several refcount block clusters ? */

static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,

    int64_t offset, int64_t length, int addend)

{

    BDRVQcowState *s = bs->opaque;

    int64_t start, last, cluster_offset;

    int64_t refcount_block_offset = 0;

    int64_t table_index = -1, old_table_index;

    int first_index = -1, last_index = -1;

    int ret;

#ifdef DEBUG_ALLOC2

    printf("update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n",

           offset, length, addend);

#endif

    if (length < 0) {

        return -EINVAL;

    } else if (length == 0) {

        return 0;

    }

    start = offset & ~(s->cluster_size - 1);

    last = (offset + length - 1) & ~(s->cluster_size - 1);

    for(cluster_offset = start; cluster_offset <= last;

        cluster_offset += s->cluster_size)

    {

        int block_index, refcount;

        int64_t cluster_index = cluster_offset >> s->cluster_bits;

        int64_t new_block;

        /* Only write refcount block to disk when we are done with it */

        old_table_index = table_index;

        table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);

        if ((old_table_index >= 0) && (table_index != old_table_index)) {

            if (write_refcount_block_entries(s, refcount_block_offset,

                first_index, last_index) < 0)

            {

                return -EIO;

            }

            first_index = -1;

            last_index = -1;

        }

        /* Load the refcount block and allocate it if needed */

        new_block = alloc_refcount_block(bs, cluster_index);

        if (new_block < 0) {

            ret = new_block;

            goto fail;

        }

        refcount_block_offset = new_block;

        /* we can update the count and save it */

        block_index = cluster_index &

            ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);

        if (first_index == -1 || block_index < first_index) {

            first_index = block_index;

        }

        if (block_index > last_index) {

            last_index = block_index;

        }

        refcount = be16_to_cpu(s->refcount_block_cache[block_index]);

        refcount += addend;

        if (refcount < 0 || refcount > 0xffff) {

            ret = -EINVAL;

            goto fail;

        }

        if (refcount == 0 && cluster_index < s->free_cluster_index) {

            s->free_cluster_index = cluster_index;

        }

        s->refcount_block_cache[block_index] = cpu_to_be16(refcount);

    }

    ret = 0;

fail:

    /* Write last changed block to disk */

    if (refcount_block_offset != 0) {

        if (write_refcount_block_entries(s, refcount_block_offset,

            first_index, last_index) < 0)

        {

            return ret < 0 ? ret : -EIO;

        }

    }

    /*

     * Try do undo any updates if an error is returned (This may succeed in

     * some cases like ENOSPC for allocating a new refcount block)

     */

    if (ret < 0) {

        int dummy;

        dummy = update_refcount(bs, offset, cluster_offset - offset, -addend);

    }

    return ret;

}

/* addend must be 1 or -1 */

static int update_cluster_refcount(BlockDriverState *bs,

                                   int64_t cluster_index,

                                   int addend)

{

    BDRVQcowState *s = bs->opaque;

    int ret;

    ret = update_refcount(bs, cluster_index << s->cluster_bits, 1, addend);

    if (ret < 0) {

        return ret;

    }

    return get_refcount(bs, cluster_index);

}

/*********************************************************/

/* cluster allocation functions */

/* return < 0 if error */

static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size)

{

    BDRVQcowState *s = bs->opaque;

    int i, nb_clusters;

    nb_clusters = size_to_clusters(s, size);

retry:

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

        int64_t i = s->free_cluster_index++;

        if (get_refcount(bs, i) != 0)

            goto retry;

    }

#ifdef DEBUG_ALLOC2

    printf("alloc_clusters: size=%" PRId64 " -> %" PRId64 "\n",

            size,

            (s->free_cluster_index - nb_clusters) << s->cluster_bits);

#endif

    return (s->free_cluster_index - nb_clusters) << s->cluster_bits;

}

int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size)

{

    int64_t offset;

    int ret;

    offset = alloc_clusters_noref(bs, size);

    ret = update_refcount(bs, offset, size, 1);

    if (ret < 0) {

        return ret;

    }

    return offset;

}

/* only used to allocate compressed sectors. We try to allocate

   contiguous sectors. size must be <= cluster_size */

int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)

{

    BDRVQcowState *s = bs->opaque;

    int64_t offset, cluster_offset;

    int free_in_cluster;

    assert(size > 0 && size <= s->cluster_size);

    if (s->free_byte_offset == 0) {

        s->free_byte_offset = qcow2_alloc_clusters(bs, s->cluster_size);

    }

 redo:

    free_in_cluster = s->cluster_size -

        (s->free_byte_offset & (s->cluster_size - 1));

    if (size <= free_in_cluster) {

        /* enough space in current cluster */

        offset = s->free_byte_offset;

        s->free_byte_offset += size;

        free_in_cluster -= size;

        if (free_in_cluster == 0)

            s->free_byte_offset = 0;

        if ((offset & (s->cluster_size - 1)) != 0)

            update_cluster_refcount(bs, offset >> s->cluster_bits, 1);

    } else {

        offset = qcow2_alloc_clusters(bs, s->cluster_size);

        cluster_offset = s->free_byte_offset & ~(s->cluster_size - 1);

        if ((cluster_offset + s->cluster_size) == offset) {

            /* we are lucky: contiguous data */

            offset = s->free_byte_offset;

            update_cluster_refcount(bs, offset >> s->cluster_bits, 1);

            s->free_byte_offset += size;

        } else {

            s->free_byte_offset = offset;

            goto redo;

        }

    }

    return offset;

}

void qcow2_free_clusters(BlockDriverState *bs,

                          int64_t offset, int64_t size)

{

    int ret;

    ret = update_refcount(bs, offset, size, -1);

    if (ret < 0) {

        fprintf(stderr, "qcow2_free_clusters failed: %s\n", strerror(-ret));

        abort();

    }

}

/*

 * free_any_clusters

 *

 * free clusters according to its type: compressed or not

 *

 */

void qcow2_free_any_clusters(BlockDriverState *bs,

    uint64_t cluster_offset, int nb_clusters)

{

    BDRVQcowState *s = bs->opaque;

    /* free the cluster */

    if (cluster_offset & QCOW_OFLAG_COMPRESSED) {

        int nb_csectors;

        nb_csectors = ((cluster_offset >> s->csize_shift) &

                       s->csize_mask) + 1;

        qcow2_free_clusters(bs,

            (cluster_offset & s->cluster_offset_mask) & ~511,

            nb_csectors * 512);

        return;

    }

    qcow2_free_clusters(bs, cluster_offset, nb_clusters << s->cluster_bits);

    return;

}

/*********************************************************/

/* snapshots and image creation */

void qcow2_create_refcount_update(QCowCreateState *s, int64_t offset,

    int64_t size)

{

    int refcount;

    int64_t start, last, cluster_offset;

    uint16_t *p;

    start = offset & ~(s->cluster_size - 1);

    last = (offset + size - 1)  & ~(s->cluster_size - 1);

    for(cluster_offset = start; cluster_offset <= last;

        cluster_offset += s->cluster_size) {

        p = &s->refcount_block[cluster_offset >> s->cluster_bits];

        refcount = be16_to_cpu(*p);

        refcount++;

        *p = cpu_to_be16(refcount);

    }

}

/* update the refcounts of snapshots and the copied flag */

int qcow2_update_snapshot_refcount(BlockDriverState *bs,

    int64_t l1_table_offset, int l1_size, int addend)

{

    BDRVQcowState *s = bs->opaque;

    uint64_t *l1_table, *l2_table, l2_offset, offset, l1_size2, l1_allocated;

    int64_t old_offset, old_l2_offset;

    int l2_size, i, j, l1_modified, l2_modified, nb_csectors, refcount;

    qcow2_l2_cache_reset(bs);

    cache_refcount_updates = 1;

    l2_table = NULL;

    l1_table = NULL;

    l1_size2 = l1_size * sizeof(uint64_t);

    if (l1_table_offset != s->l1_table_offset) {

        if (l1_size2 != 0) {

            l1_table = qemu_mallocz(align_offset(l1_size2, 512));

        } else {

            l1_table = NULL;

        }

        l1_allocated = 1;

        if (bdrv_pread(s->hd, l1_table_offset,

                       l1_table, l1_size2) != l1_size2)

            goto fail;

        for(i = 0;i < l1_size; i++)

            be64_to_cpus(&l1_table[i]);

    } else {

        assert(l1_size == s->l1_size);

        l1_table = s->l1_table;

        l1_allocated = 0;

    }

    l2_size = s->l2_size * sizeof(uint64_t);

    l2_table = qemu_malloc(l2_size);

    l1_modified = 0;

    for(i = 0; i < l1_size; i++) {

        l2_offset = l1_table[i];

        if (l2_offset) {

            old_l2_offset = l2_offset;

            l2_offset &= ~QCOW_OFLAG_COPIED;

            l2_modified = 0;

            if (bdrv_pread(s->hd, l2_offset, l2_table, l2_size) != l2_size)

                goto fail;

            for(j = 0; j < s->l2_size; j++) {

                offset = be64_to_cpu(l2_table[j]);

                if (offset != 0) {

                    old_offset = offset;

                    offset &= ~QCOW_OFLAG_COPIED;

                    if (offset & QCOW_OFLAG_COMPRESSED) {

                        nb_csectors = ((offset >> s->csize_shift) &

                                       s->csize_mask) + 1;

                        if (addend != 0) {

                            int ret;

                            ret = update_refcount(bs,

                                (offset & s->cluster_offset_mask) & ~511,

                                nb_csectors * 512, addend);

                            if (ret < 0) {

                                goto fail;

                            }

                        }

                        /* compressed clusters are never modified */

                        refcount = 2;

                    } else {

                        if (addend != 0) {

                            refcount = update_cluster_refcount(bs, offset >> s->cluster_bits, addend);

                        } else {

                            refcount = get_refcount(bs, offset >> s->cluster_bits);

                        }

                    }

                    if (refcount == 1) {

                        offset |= QCOW_OFLAG_COPIED;

                    }

                    if (offset != old_offset) {

                        l2_table[j] = cpu_to_be64(offset);

                        l2_modified = 1;

                    }

                }

            }

            if (l2_modified) {

                if (bdrv_pwrite(s->hd,

                                l2_offset, l2_table, l2_size) != l2_size)

                    goto fail;

            }

            if (addend != 0) {

                refcount = update_cluster_refcount(bs, l2_offset >> s->cluster_bits, addend);

            } else {

                refcount = get_refcount(bs, l2_offset >> s->cluster_bits);

            }

            if (refcount == 1) {

                l2_offset |= QCOW_OFLAG_COPIED;

            }

            if (l2_offset != old_l2_offset) {

                l1_table[i] = l2_offset;

                l1_modified = 1;

            }

        }

    }

    if (l1_modified) {

        for(i = 0; i < l1_size; i++)

            cpu_to_be64s(&l1_table[i]);

        if (bdrv_pwrite(s->hd, l1_table_offset, l1_table,

                        l1_size2) != l1_size2)

            goto fail;

        for(i = 0; i < l1_size; i++)

            be64_to_cpus(&l1_table[i]);

    }

    if (l1_allocated)

        qemu_free(l1_table);

    qemu_free(l2_table);

    cache_refcount_updates = 0;

    write_refcount_block(s);

    return 0;

 fail:

    if (l1_allocated)

        qemu_free(l1_table);

    qemu_free(l2_table);

    cache_refcount_updates = 0;

    write_refcount_block(s);

    return -EIO;

}

/*********************************************************/

/* refcount checking functions */

/*

 * Increases the refcount for a range of clusters in a given refcount table.

 * This is used to construct a temporary refcount table out of L1 and L2 tables

 * which can be compared the the refcount table saved in the image.

 *

 * Returns the number of errors in the image that were found

 */

static int inc_refcounts(BlockDriverState *bs,

                          uint16_t *refcount_table,

                          int refcount_table_size,

                          int64_t offset, int64_t size)

{

    BDRVQcowState *s = bs->opaque;

    int64_t start, last, cluster_offset;

    int k;

    int errors = 0;

    if (size <= 0)

        return 0;

    start = offset & ~(s->cluster_size - 1);

    last = (offset + size - 1) & ~(s->cluster_size - 1);

    for(cluster_offset = start; cluster_offset <= last;

        cluster_offset += s->cluster_size) {

        k = cluster_offset >> s->cluster_bits;

        if (k < 0 || k >= refcount_table_size) {

            fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n",

                cluster_offset);

            errors++;

        } else {

            if (++refcount_table[k] == 0) {

                fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64

                    "\n", cluster_offset);

                errors++;

            }

        }

    }

    return errors;

}

/*

 * Increases the refcount in the given refcount table for the all clusters

 * referenced in the L2 table. While doing so, performs some checks on L2

 * entries.

 *

 * Returns the number of errors found by the checks or -errno if an internal

 * error occurred.

 */

static int check_refcounts_l2(BlockDriverState *bs,

    uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset,

    int check_copied)

{

    BDRVQcowState *s = bs->opaque;

    uint64_t *l2_table, offset;

    int i, l2_size, nb_csectors, refcount;

    int errors = 0;

    /* Read L2 table from disk */

    l2_size = s->l2_size * sizeof(uint64_t);

    l2_table = qemu_malloc(l2_size);

    if (bdrv_pread(s->hd, l2_offset, l2_table, l2_size) != l2_size)

        goto fail;

    /* Do the actual checks */

    for(i = 0; i < s->l2_size; i++) {

        offset = be64_to_cpu(l2_table[i]);

        if (offset != 0) {

            if (offset & QCOW_OFLAG_COMPRESSED) {

                /* Compressed clusters don't have QCOW_OFLAG_COPIED */

                if (offset & QCOW_OFLAG_COPIED) {

                    fprintf(stderr, "ERROR: cluster %" PRId64 ": "

                        "copied flag must never be set for compressed "

                        "clusters\n", offset >> s->cluster_bits);

                    offset &= ~QCOW_OFLAG_COPIED;

                    errors++;

                }

                /* Mark cluster as used */

                nb_csectors = ((offset >> s->csize_shift) &

                               s->csize_mask) + 1;

                offset &= s->cluster_offset_mask;

                errors += inc_refcounts(bs, refcount_table,

                              refcount_table_size,

                              offset & ~511, nb_csectors * 512);

            } else {

                /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */

                if (check_copied) {

                    uint64_t entry = offset;

                    offset &= ~QCOW_OFLAG_COPIED;

                    refcount = get_refcount(bs, offset >> s->cluster_bits);

                    if ((refcount == 1) != ((entry & QCOW_OFLAG_COPIED) != 0)) {

                        fprintf(stderr, "ERROR OFLAG_COPIED: offset=%"

                            PRIx64 " refcount=%d\n", entry, refcount);

                        errors++;

                    }

                }

                /* Mark cluster as used */

                offset &= ~QCOW_OFLAG_COPIED;

                errors += inc_refcounts(bs, refcount_table,

                              refcount_table_size,

                              offset, s->cluster_size);

                /* Correct offsets are cluster aligned */

                if (offset & (s->cluster_size - 1)) {

                    fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not "

                        "properly aligned; L2 entry corrupted.\n", offset);

                    errors++;

                }

            }

        }

    }

    qemu_free(l2_table);

    return errors;

fail:

    fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");

    qemu_free(l2_table);

    return -EIO;

}

/*

 * Increases the refcount for the L1 table, its L2 tables and all referenced

 * clusters in the given refcount table. While doing so, performs some checks

 * on L1 and L2 entries.

 *

 * Returns the number of errors found by the checks or -errno if an internal

 * error occurred.

 */

static int check_refcounts_l1(BlockDriverState *bs,

                              uint16_t *refcount_table,

                              int refcount_table_size,

                              int64_t l1_table_offset, int l1_size,

                              int check_copied)

{

    BDRVQcowState *s = bs->opaque;

    uint64_t *l1_table, l2_offset, l1_size2;

    int i, refcount, ret;

    int errors = 0;

    l1_size2 = l1_size * sizeof(uint64_t);

    /* Mark L1 table as used */

    errors += inc_refcounts(bs, refcount_table, refcount_table_size,

                  l1_table_offset, l1_size2);

    /* Read L1 table entries from disk */

    if (l1_size2 == 0) {

        l1_table = NULL;

    } else {

        l1_table = qemu_malloc(l1_size2);

        if (bdrv_pread(s->hd, l1_table_offset,

                       l1_table, l1_size2) != l1_size2)

            goto fail;

        for(i = 0;i < l1_size; i++)

            be64_to_cpus(&l1_table[i]);

    }

    /* Do the actual checks */

    for(i = 0; i < l1_size; i++) {

        l2_offset = l1_table[i];

        if (l2_offset) {

            /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */

            if (check_copied) {

                refcount = get_refcount(bs, (l2_offset & ~QCOW_OFLAG_COPIED)

                    >> s->cluster_bits);

                if ((refcount == 1) != ((l2_offset & QCOW_OFLAG_COPIED) != 0)) {

                    fprintf(stderr, "ERROR OFLAG_COPIED: l2_offset=%" PRIx64

                        " refcount=%d\n", l2_offset, refcount);

                    errors++;

                }

            }

            /* Mark L2 table as used */

            l2_offset &= ~QCOW_OFLAG_COPIED;

            errors += inc_refcounts(bs, refcount_table,

                          refcount_table_size,

                          l2_offset,

                          s->cluster_size);

            /* L2 tables are cluster aligned */

            if (l2_offset & (s->cluster_size - 1)) {

                fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not "

                    "cluster aligned; L1 entry corrupted\n", l2_offset);

                errors++;

            }

            /* Process and check L2 entries */

            ret = check_refcounts_l2(bs, refcount_table, refcount_table_size,

                l2_offset, check_copied);

            if (ret < 0) {

                goto fail;

            }

            errors += ret;

        }

    }

    qemu_free(l1_table);

    return errors;

fail:

    fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");

    qemu_free(l1_table);

    return -EIO;

}

/*

 * Checks an image for refcount consistency.

 *

 * Returns 0 if no errors are found, the number of errors in case the image is

 * detected as corrupted, and -errno when an internal error occured.

 */

int qcow2_check_refcounts(BlockDriverState *bs)

{

    BDRVQcowState *s = bs->opaque;

    int64_t size;

    int nb_clusters, refcount1, refcount2, i;

    QCowSnapshot *sn;

    uint16_t *refcount_table;

    int ret, errors = 0;

    size = bdrv_getlength(s->hd);

    nb_clusters = size_to_clusters(s, size);

    refcount_table = qemu_mallocz(nb_clusters * sizeof(uint16_t));

    /* header */

    errors += inc_refcounts(bs, refcount_table, nb_clusters,

                  0, s->cluster_size);

    /* current L1 table */

    ret = check_refcounts_l1(bs, refcount_table, nb_clusters,

                       s->l1_table_offset, s->l1_size, 1);

    if (ret < 0) {

        return ret;

    }

    errors += ret;

    /* snapshots */

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

        sn = s->snapshots + i;

        check_refcounts_l1(bs, refcount_table, nb_clusters,