Re: [Qemu-devel] [PATCH v3 6/6] vmdk: Update metadata for multiple clusters

[Fam Zheng <famz@redhat.com>]

On Sat, 04/01 20:14, Ashijeet Acharya wrote:
> Include a next pointer in VmdkMetaData struct to point to the previous
> allocated L2 table. Modify vmdk_L2update to start updating metadata for
> allocation of multiple clusters at once.
> 
> Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>

This is the metadata part of the coalesed allocation. I think patch 3 is
functionally incomplete without these changes, and is perhaps broken because
metadata is not handled correctly.

Such an "intermediate functional regression" is not good in a series, which we
need to avoid.

> ---
>  block/vmdk.c | 136 ++++++++++++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 111 insertions(+), 25 deletions(-)
> 
> diff --git a/block/vmdk.c b/block/vmdk.c
> index 9456ddd..c7675db 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -137,6 +137,8 @@ typedef struct VmdkMetaData {
>      int valid;
>      uint32_t *l2_cache_entry;
>      uint32_t nb_clusters;
> +    uint32_t offset;
> +    struct VmdkMetaData *next;
>  } VmdkMetaData;
>  
>  typedef struct VmdkGrainMarker {
> @@ -263,6 +265,12 @@ static inline uint64_t size_to_clusters(VmdkExtent *extent, uint64_t size)
>      return (DIV_ROUND_UP(size + round_off_size, BDRV_SECTOR_SIZE * 128) - 1);
>  }
>  
> +static inline int64_t vmdk_align_offset(int64_t offset, int n)
> +{
> +    offset = (offset + n - 1) & ~(n - 1);
> +    return offset;
> +}
> +
>  static uint32_t vmdk_read_cid(BlockDriverState *bs, int parent)
>  {
>      char *desc;
> @@ -1037,29 +1045,88 @@ static void vmdk_refresh_limits(BlockDriverState *bs, Error **errp)
>      }
>  }
>  
> -static int vmdk_L2update(VmdkExtent *extent, VmdkMetaData *m_data,
> -                         uint32_t offset)
> +static int vmdk_alloc_cluster_link_l2(VmdkExtent *extent,
> +                                      VmdkMetaData *m_data, bool zeroed)
>  {
> -    offset = cpu_to_le32(offset);
> +    int i;
> +    uint32_t offset, temp_offset;
> +    int *l2_table_array;
> +    int l2_array_size;
> +
> +    if (zeroed) {
> +        temp_offset = VMDK_GTE_ZEROED;
> +    } else {
> +        temp_offset = m_data->offset;
> +    }
> +
> +    temp_offset = cpu_to_le32(temp_offset);
> +
> +    l2_array_size = sizeof(uint32_t) * m_data->nb_clusters;
> +    l2_table_array = qemu_try_blockalign(extent->file->bs,
> +                                    vmdk_align_offset(l2_array_size, 512));

Indentation is off.

Use QEMU_ALIGN_UP, instead of vmdk_align_offset.

512 is a magic number, use BDRV_SECTOR_SIZE.

> +    if (l2_table_array == NULL) {
> +        return VMDK_ERROR;
> +    }
> +    memset(l2_table_array, 0, vmdk_align_offset(l2_array_size, 512));
> +
>      /* update L2 table */
> +    offset = temp_offset;
> +    for (i = 0; i < m_data->nb_clusters; i++) {
> +        l2_table_array[i] = offset;
> +        if (!zeroed) {
> +            offset += 128;

Something is going wrong here with endianness on BE host, I believe.

> +        }
> +    }
> +
>      if (bdrv_pwrite_sync(extent->file,
> -                ((int64_t)m_data->l2_offset * 512)
> -                    + (m_data->l2_index * sizeof(offset)),
> -                &offset, sizeof(offset)) < 0) {
> +            ((int64_t)m_data->l2_offset * 512)
> +                + ((m_data->l2_index) * sizeof(offset)),
> +                         l2_table_array, l2_array_size) < 0) {

You can fix the indentation while changing these lines. If not, don't change it,
or at least don't make it uglier.

>          return VMDK_ERROR;
>      }
> +
>      /* 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(offset)),
> -                    &offset, sizeof(offset)) < 0) {
> +                        + ((m_data->l2_index) * sizeof(offset)),
> +                                l2_table_array, l2_array_size) < 0) {

Same here.

>              return VMDK_ERROR;
>          }
>      }
> +
> +    offset = temp_offset;
>      if (m_data->l2_cache_entry) {
> -        *m_data->l2_cache_entry = offset;
> +        for (i = 0; i < m_data->nb_clusters; i++) {
> +            *m_data->l2_cache_entry = offset;
> +            m_data->l2_cache_entry++;
> +
> +            if (!zeroed) {
> +                offset += 128;
> +            }
> +        }
> +    }
> +
> +    qemu_vfree(l2_table_array);
> +    return VMDK_OK;
> +}
> +
> +static int vmdk_L2update(VmdkExtent *extent, VmdkMetaData *m_data,
> +                         bool zeroed)
> +{
> +    int ret;
> +
> +    while (m_data->next != NULL) {
> +        VmdkMetaData *next;
> +
> +        ret = vmdk_alloc_cluster_link_l2(extent, m_data, zeroed);
> +        if (ret < 0) {
> +            return ret;
> +        }
> +
> +        next = m_data->next;
> +        m_data = next;

Why not simply "m_data = m_data->next" and drop "next" variable?

>      }
>  
>      return VMDK_OK;
> @@ -1271,7 +1338,7 @@ exit:
>   */
>  static int handle_alloc(BlockDriverState *bs, VmdkExtent *extent,
>                          uint64_t offset, uint64_t *cluster_offset,
> -                        int64_t *bytes, VmdkMetaData *m_data,
> +                        int64_t *bytes, VmdkMetaData **m_data,
>                          bool allocate, uint32_t *total_alloc_clusters)
>  {
>      int l1_index, l2_offset, l2_index;
> @@ -1280,6 +1347,7 @@ static int handle_alloc(BlockDriverState *bs, VmdkExtent *extent,
>      uint32_t nb_clusters;
>      bool zeroed = false;
>      uint64_t skip_start_bytes, skip_end_bytes;
> +    VmdkMetaData *old_m_data;
>      int ret;
>  
>      ret = get_cluster_table(extent, offset, &l1_index, &l2_offset,
> @@ -1330,13 +1398,21 @@ static int handle_alloc(BlockDriverState *bs, VmdkExtent *extent,
>          if (ret < 0) {
>              return ret;
>          }
> -        if (m_data) {
> -            m_data->valid = 1;
> -            m_data->l1_index = l1_index;
> -            m_data->l2_index = l2_index;
> -            m_data->l2_offset = l2_offset;
> -            m_data->l2_cache_entry = &l2_table[l2_index];
> -            m_data->nb_clusters = nb_clusters;
> +
> +        if (*m_data) {
> +            old_m_data = *m_data;
> +            *m_data = g_malloc0(sizeof(**m_data));
> +
> +            **m_data = (VmdkMetaData) {
> +                .valid            =    1,
> +                .l1_index         =    l1_index,
> +                .l2_index         =    l2_index,
> +                .l2_offset        =    l2_offset,
> +                .l2_cache_entry   =    &l2_table[l2_index],
> +                .nb_clusters      =    nb_clusters,
> +                .offset           =    cluster_sector,
> +                .next             =    old_m_data,
> +            };

I think if the new m_data can be merged into the old, there is no need to
allocate a new one.

>          }
>      }
>      *cluster_offset = cluster_sector << BDRV_SECTOR_BITS;
> @@ -1365,7 +1441,7 @@ static int handle_alloc(BlockDriverState *bs, VmdkExtent *extent,
>   */
>  static int vmdk_alloc_cluster_offset(BlockDriverState *bs,
>                                       VmdkExtent *extent,
> -                                     VmdkMetaData *m_data, uint64_t offset,
> +                                     VmdkMetaData **m_data, uint64_t offset,
>                                       bool allocate, uint64_t *cluster_offset,
>                                       int64_t bytes,
>                                       uint32_t *total_alloc_clusters)
> @@ -1385,8 +1461,8 @@ static int vmdk_alloc_cluster_offset(BlockDriverState *bs,
>      new_cluster_offset = 0;
>      *cluster_offset = 0;
>      n_bytes = 0;
> -    if (m_data) {
> -        m_data->valid = 0;
> +    if (*m_data) {
> +        (*m_data)->valid = 0;
>      }
>  
>      /* due to L2 table margins all bytes may not get allocated at once */
> @@ -1768,9 +1844,11 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t offset,
>      uint64_t cluster_offset;
>      uint64_t bytes_done = 0;
>      uint64_t extent_size;
> -    VmdkMetaData m_data;
> +    VmdkMetaData *m_data;
>      uint32_t total_alloc_clusters = 0;
>  
> +    m_data = g_malloc0(sizeof(*m_data));
> +
>      if (DIV_ROUND_UP(offset, BDRV_SECTOR_SIZE) > bs->total_sectors) {
>          error_report("Wrong offset: offset=0x%" PRIx64
>                       " total_sectors=0x%" PRIx64,
> @@ -1779,6 +1857,7 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t offset,
>      }
>  
>      while (bytes > 0) {
> +        m_data->next = NULL;
>          extent = find_extent(s, offset >> BDRV_SECTOR_BITS, extent);
>          if (!extent) {
>              return -EIO;
> @@ -1825,7 +1904,7 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t offset,
>                                          total_alloc_clusters;
>                  if (!zero_dry_run) {
>                      /* update L2 tables */
> -                    if (vmdk_L2update(extent, &m_data, VMDK_GTE_ZEROED)
> +                    if (vmdk_L2update(extent, m_data, zeroed)
>                              != VMDK_OK) {
>                          return -EIO;
>                      }
> @@ -1839,10 +1918,9 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t offset,
>              if (ret) {
>                  return ret;
>              }
> -            if (m_data.valid) {
> +            if (m_data->valid) {
>                  /* update L2 tables */
> -                if (vmdk_L2update(extent, &m_data,
> -                                  cluster_offset >> BDRV_SECTOR_BITS)
> +                if (vmdk_L2update(extent, m_data, zeroed)
>                          != VMDK_OK) {
>                      return -EIO;
>                  }
> @@ -1852,6 +1930,13 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t offset,
>          offset += n_bytes;
>          bytes_done += n_bytes;
>  
> +        while (m_data->next != NULL) {
> +            VmdkMetaData *next;
> +            next = m_data->next;
> +            g_free(m_data);
> +            m_data = next;
> +        }
> +
>          /* update CID on the first write every time the virtual disk is
>           * opened */
>          if (!s->cid_updated) {
> @@ -1862,6 +1947,7 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t offset,
>              s->cid_updated = true;
>          }
>      }
> +    g_free(m_data);

This is weird, you free all but the last m_data with a while loop, a few lines
above, and this one with a separate g_free().

Please use one loop:

    for (p = m_data; p; p = next) {
        next = p->next;
        g_free(p);
    }

>      return 0;
>  }
>  
> -- 
> 2.6.2
>