qcow2: Split out refcount handling

qcow2-refcount.c contains all functions which are related to cluster
allocation and management in the image file. A large part of this is the
reference counting of these clusters.

Also a header file qcow2.h is introduced which will contain the interface of
the split qcow2 modules.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 2 insertions, 869 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index 14d8751a9..91903fe59 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -26,6 +26,7 @@
 #include "module.h"
 #include <zlib.h>
 #include "aes.h"
+#include "block/qcow2.h"
 
 /*
   Differences with QCOW:
@@ -47,40 +48,6 @@
 //#define DEBUG_ALLOC2
 //#define DEBUG_EXT
 
-#define QCOW_MAGIC (('Q' << 24) | ('F' << 16) | ('I' << 8) | 0xfb)
-#define QCOW_VERSION 2
-
-#define QCOW_CRYPT_NONE 0
-#define QCOW_CRYPT_AES  1
-
-#define QCOW_MAX_CRYPT_CLUSTERS 32
-
-/* indicate that the refcount of the referenced cluster is exactly one. */
-#define QCOW_OFLAG_COPIED     (1LL << 63)
-/* indicate that the cluster is compressed (they never have the copied flag) */
-#define QCOW_OFLAG_COMPRESSED (1LL << 62)
-
-#define REFCOUNT_SHIFT 1 /* refcount size is 2 bytes */
-
-#define MIN_CLUSTER_BITS 9
-#define MAX_CLUSTER_BITS 16
-
-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;
-} QCowHeader;
-
 
 typedef struct {
     uint32_t magic;
@@ -110,77 +77,12 @@ typedef struct __attribute__((packed)) QCowSnapshotHeader {
     /* name follows  */
 } QCowSnapshotHeader;
 
-#define L2_CACHE_SIZE 16
-
-typedef struct QCowSnapshot {
-    uint64_t l1_table_offset;
-    uint32_t l1_size;
-    char *id_str;
-    char *name;
-    uint32_t vm_state_size;
-    uint32_t date_sec;
-    uint32_t date_nsec;
-    uint64_t vm_clock_nsec;
-} QCowSnapshot;
-
-typedef struct BDRVQcowState {
-    BlockDriverState *hd;
-    int cluster_bits;
-    int cluster_size;
-    int cluster_sectors;
-    int l2_bits;
-    int l2_size;
-    int l1_size;
-    int l1_vm_state_index;
-    int csize_shift;
-    int csize_mask;
-    uint64_t cluster_offset_mask;
-    uint64_t l1_table_offset;
-    uint64_t *l1_table;
-    uint64_t *l2_cache;
-    uint64_t l2_cache_offsets[L2_CACHE_SIZE];
-    uint32_t l2_cache_counts[L2_CACHE_SIZE];
-    uint8_t *cluster_cache;
-    uint8_t *cluster_data;
-    uint64_t cluster_cache_offset;
-
-    uint64_t *refcount_table;
-    uint64_t refcount_table_offset;
-    uint32_t refcount_table_size;
-    uint64_t refcount_block_cache_offset;
-    uint16_t *refcount_block_cache;
-    int64_t free_cluster_index;
-    int64_t free_byte_offset;
-
-    uint32_t crypt_method; /* current crypt method, 0 if no key yet */
-    uint32_t crypt_method_header;
-    AES_KEY aes_encrypt_key;
-    AES_KEY aes_decrypt_key;
-    uint64_t snapshots_offset;
-    int snapshots_size;
-    int nb_snapshots;
-    QCowSnapshot *snapshots;
-} BDRVQcowState;
 
 static int decompress_cluster(BDRVQcowState *s, uint64_t cluster_offset);
 static int qcow_read(BlockDriverState *bs, int64_t sector_num,
                      uint8_t *buf, int nb_sectors);
 static int qcow_read_snapshots(BlockDriverState *bs);
 static void qcow_free_snapshots(BlockDriverState *bs);
-static int refcount_init(BlockDriverState *bs);
-static void refcount_close(BlockDriverState *bs);
-static int get_refcount(BlockDriverState *bs, int64_t cluster_index);
-static int update_cluster_refcount(BlockDriverState *bs,
-                                   int64_t cluster_index,
-                                   int addend);
-static int update_refcount(BlockDriverState *bs,
-                            int64_t offset, int64_t length,
-                            int addend);
-static int64_t alloc_clusters(BlockDriverState *bs, int64_t size);
-static int64_t alloc_bytes(BlockDriverState *bs, int size);
-static void free_clusters(BlockDriverState *bs,
-                          int64_t offset, int64_t size);
-static int check_refcounts(BlockDriverState *bs);
 
 static int qcow_probe(const uint8_t *buf, int buf_size, const char *filename)
 {
@@ -482,7 +384,7 @@ static int copy_sectors(BlockDriverState *bs, uint64_t start_sect,
     return 0;
 }
 
-static void l2_cache_reset(BlockDriverState *bs)
+void l2_cache_reset(BlockDriverState *bs)
 {
     BDRVQcowState *s = bs->opaque;
 
@@ -691,11 +593,6 @@ static uint64_t *l2_allocate(BlockDriverState *bs, int l1_index)
     return l2_table;
 }
 
-static int size_to_clusters(BDRVQcowState *s, int64_t size)
-{
-    return (size + (s->cluster_size - 1)) >> s->cluster_bits;
-}
-
 static int count_contiguous_clusters(uint64_t nb_clusters, int cluster_size,
         uint64_t *l2_table, uint64_t start, uint64_t mask)
 {
@@ -1522,35 +1419,6 @@ static void qcow_close(BlockDriverState *bs)
     bdrv_delete(s->hd);
 }
 
-/* XXX: use std qcow open function ? */
-typedef struct QCowCreateState {
-    int cluster_size;
-    int cluster_bits;
-    uint16_t *refcount_block;
-    uint64_t *refcount_table;
-    int64_t l1_table_offset;
-    int64_t refcount_table_offset;
-    int64_t refcount_block_offset;
-} QCowCreateState;
-
-static void 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);
-    }
-}
-
 static int get_bits_from_size(size_t size)
 {
     int res = 0;
@@ -1834,117 +1702,6 @@ static int qcow_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
 /*********************************************************/
 /* snapshot support */
 
-/* update the refcounts of snapshots and the copied flag */
-static int 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;
-
-    l2_cache_reset(bs);
-
-    l2_table = NULL;
-    l1_table = NULL;
-    l1_size2 = l1_size * sizeof(uint64_t);
-    l1_allocated = 0;
-    if (l1_table_offset != s->l1_table_offset) {
-        l1_table = qemu_malloc(l1_size2);
-        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)
-                            update_refcount(bs, (offset & s->cluster_offset_mask) & ~511,
-                                            nb_csectors * 512, addend);
-                        /* 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);
-    return 0;
- fail:
-    if (l1_allocated)
-        qemu_free(l1_table);
-    qemu_free(l2_table);
-    return -EIO;
-}
 
 static void qcow_free_snapshots(BlockDriverState *bs)
 {
@@ -2306,630 +2063,6 @@ static int qcow_snapshot_list(BlockDriverState *bs,
     return s->nb_snapshots;
 }
 
-/*********************************************************/
-/* refcount handling */
-
-static int 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;
-}
-
-static void 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;
-    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]);
-}
-
-/* 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=%lld -> %lld\n",
-            size,
-            (s->free_cluster_index - nb_clusters) << s->cluster_bits);
-#endif
-    return (s->free_cluster_index - nb_clusters) << s->cluster_bits;
-}
-
-static int64_t alloc_clusters(BlockDriverState *bs, int64_t size)
-{
-    int64_t offset;
-
-    offset = alloc_clusters_noref(bs, size);
-    update_refcount(bs, offset, size, 1);
-    return offset;
-}
-
-/* only used to allocate compressed sectors. We try to allocate
-   contiguous sectors. size must be <= cluster_size */
-static int64_t 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 = 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 = 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;
-}
-
-static void free_clusters(BlockDriverState *bs,
-                          int64_t offset, int64_t size)
-{
-    update_refcount(bs, offset, size, -1);
-}
-
-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);
-    if (bdrv_pwrite(s->hd, offsetof(QCowHeader, refcount_table_offset),
-                    data, sizeof(data)) != 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);
-    free_clusters(bs, old_table_offset, old_table_size * sizeof(uint64_t));
-    return 0;
- fail:
-    free_clusters(bs, table_offset, new_table_size2);
-    qemu_free(new_table);
-    return -EIO;
-}
-
-
-static int64_t alloc_refcount_block(BlockDriverState *bs, int64_t cluster_index)
-{
-    BDRVQcowState *s = bs->opaque;
-    int64_t offset, refcount_block_offset;
-    int ret, refcount_table_index;
-    uint64_t data64;
-
-    /* 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) {
-        /* 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);
-    } 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;
-}
-
-/* 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);
-}
-
-/* XXX: cache several refcount block clusters ? */
-static int 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;
-
-#ifdef DEBUG_ALLOC2
-    printf("update_refcount: offset=%lld size=%lld addend=%d\n",
-           offset, length, addend);
-#endif
-    if (length <= 0)
-        return -EINVAL;
-    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;
-
-        /* 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)) {
-            size_t size = (last_index - first_index + 1) << REFCOUNT_SHIFT;
-            if (bdrv_pwrite(s->hd,
-                refcount_block_offset + (first_index << REFCOUNT_SHIFT),
-                &s->refcount_block_cache[first_index], size) != size)
-            {
-                return -EIO;
-            }
-
-            first_index = -1;
-            last_index = -1;
-        }
-
-        /* Load the refcount block and allocate it if needed */
-        refcount_block_offset = alloc_refcount_block(bs, cluster_index);
-        if (refcount_block_offset < 0) {
-            return refcount_block_offset;
-        }
-
-        /* 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)
-            return -EINVAL;
-        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);
-    }
-
-    /* Write last changed block to disk */
-    if (refcount_block_offset != 0) {
-        size_t size = (last_index - first_index + 1) << 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;
-}
-
-/*
- * 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 */
-    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.
- */
-static int 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,
-                           sn->l1_table_offset, sn->l1_size, 0);
-    }
-    errors += inc_refcounts(bs, refcount_table, nb_clusters,
-                  s->snapshots_offset, s->snapshots_size);
-
-    /* refcount data */
-    errors += inc_refcounts(bs, refcount_table, nb_clusters,
-                  s->refcount_table_offset,
-                  s->refcount_table_size * sizeof(uint64_t));
-    for(i = 0; i < s->refcount_table_size; i++) {
-        int64_t offset;
-        offset = s->refcount_table[i];
-        if (offset != 0) {
-            errors += inc_refcounts(bs, refcount_table, nb_clusters,
-                          offset, s->cluster_size);
-        }
-    }
-
-    /* compare ref counts */
-    for(i = 0; i < nb_clusters; i++) {
-        refcount1 = get_refcount(bs, i);
-        refcount2 = refcount_table[i];
-        if (refcount1 != refcount2) {
-            fprintf(stderr, "ERROR cluster %d refcount=%d reference=%d\n",
-                   i, refcount1, refcount2);
-            errors++;
-        }
-    }
-
-    qemu_free(refcount_table);
-
-    return errors;
-}
-
 static int qcow_check(BlockDriverState *bs)
 {
     return check_refcounts(bs);