Re: [Qemu-devel] [PATCH v4 4/8] vmdk: Factor out metadata loading code out of vmdk_get_cluster_offset()

[Fam Zheng <famz@redhat.com>]

On Sat, 04/22 10:43, Ashijeet Acharya wrote:
> Move the cluster tables loading code out of the existing
> vmdk_get_cluster_offset() function and implement it in separate
> get_cluster_table() and vmdk_L2load() functions. This patch will help

Now vmdk_L2load is in lower case, "vmdk_l2load".

> us avoid code duplication in future patches of this series.

Bikeshedding: "of this series" is meaningful now, but not quite so once this
patch becomes a commit in qemu.git - the series information will be missing.

> 
> Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
> ---
>  block/vmdk.c | 153 ++++++++++++++++++++++++++++++++++++++++-------------------
>  1 file changed, 105 insertions(+), 48 deletions(-)
> 
> diff --git a/block/vmdk.c b/block/vmdk.c
> index f403981..4cee868 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -1143,6 +1143,105 @@ static int vmdk_L2update(VmdkExtent *extent, VmdkMetaData *m_data,
>      return VMDK_OK;
>  }
>  
> +/*
> + * vmdk_l2load
> + *
> + * Load a new L2 table into memory. If the table is in the cache, the cache
> + * is used; otherwise the L2 table is loaded from the image file.
> + *
> + * Returns:
> + *   VMDK_OK:       on success
> + *   VMDK_ERROR:    in error cases
> + */
> +static int vmdk_l2load(VmdkExtent *extent, uint64_t offset, int l2_offset,
> +                       uint32_t **new_l2_table, int *new_l2_index)
> +{
> +    int min_index, i, j;
> +    uint32_t *l2_table;
> +    uint32_t min_count;
> +
> +    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] == UINT32_MAX) {
> +                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 = UINT32_MAX;
> +    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)
> +            ) != extent->l2_size * sizeof(uint32_t)) {
> +        return VMDK_ERROR;
> +    }
> +
> +    extent->l2_cache_offsets[min_index] = l2_offset;
> +    extent->l2_cache_counts[min_index] = 1;
> +found:
> +    *new_l2_index = ((offset >> 9) / extent->cluster_sectors) % extent->l2_size;
> +    *new_l2_table = l2_table;
> +
> +    return VMDK_OK;
> +}
> +
> +/*
> + * get_cluster_table
> + *
> + * for a given offset, load (and allocate if needed) the l2 table.

More consistent if you capitalize the first letter "For".

> + *
> + * Returns:
> + *   VMDK_OK:        on success
> + *
> + *   VMDK_UNALLOC:   if cluster is not mapped
> + *
> + *   VMDK_ERROR:     in error cases
> + */
> +static int get_cluster_table(VmdkExtent *extent, uint64_t offset,
> +                             int *new_l1_index, int *new_l2_offset,
> +                             int *new_l2_index, uint32_t **new_l2_table)
> +{
> +    int l1_index, l2_offset, l2_index;
> +    uint32_t *l2_table;
> +    int ret;
> +
> +    offset -= (extent->end_sector - extent->sectors) * SECTOR_SIZE;
> +    l1_index = (offset >> 9) / extent->l1_entry_sectors;
> +    if (l1_index >= extent->l1_size) {
> +        return VMDK_ERROR;
> +    }
> +    l2_offset = extent->l1_table[l1_index];
> +    if (!l2_offset) {
> +        return VMDK_UNALLOC;
> +    }
> +
> +    ret = vmdk_l2load(extent, offset, l2_offset, &l2_table, &l2_index);
> +    if (ret < 0) {
> +        return ret;
> +    }
> +
> +    *new_l1_index = l1_index;
> +    *new_l2_offset = l2_offset;
> +    *new_l2_index = l2_index;
> +    *new_l2_table = l2_table;
> +
> +    return VMDK_OK;
> +}
> +
>  /**
>   * vmdk_get_cluster_offset
>   *
> @@ -1172,66 +1271,24 @@ static int vmdk_get_cluster_offset(BlockDriverState *bs,
>                                     uint64_t skip_start_bytes,
>                                     uint64_t skip_end_bytes)
>  {
> -    unsigned int l1_index, l2_offset, l2_index;
> -    int min_index, i, j;
> -    uint32_t min_count, *l2_table;
> +    int l1_index, l2_offset, l2_index;
> +    uint32_t *l2_table;
>      bool zeroed = false;
>      int64_t ret;
>      int64_t cluster_sector;
>  
> -    if (m_data) {
> -        m_data->valid = 0;
> -    }
>      if (extent->flat) {
>          *cluster_offset = extent->flat_start_offset;
>          return VMDK_OK;
>      }
>  
> -    offset -= (extent->end_sector - extent->sectors) * SECTOR_SIZE;
> -    l1_index = (offset >> 9) / extent->l1_entry_sectors;
> -    if (l1_index >= extent->l1_size) {
> -        return VMDK_ERROR;
> -    }
> -    l2_offset = extent->l1_table[l1_index];
> -    if (!l2_offset) {
> -        return VMDK_UNALLOC;
> -    }
> -    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)
> -            ) != extent->l2_size * sizeof(uint32_t)) {
> -        return VMDK_ERROR;
> +    ret = get_cluster_table(extent, offset, &l1_index, &l2_offset,
> +                            &l2_index, &l2_table);
> +    if (ret < 0) {
> +        return ret;
>      }
>  
> -    extent->l2_cache_offsets[min_index] = l2_offset;
> -    extent->l2_cache_counts[min_index] = 1;
> - found:
> -    l2_index = ((offset >> 9) / extent->cluster_sectors) % extent->l2_size;
>      cluster_sector = le32_to_cpu(l2_table[l2_index]);
> -
>      if (extent->has_zero_grain && cluster_sector == VMDK_GTE_ZEROED) {
>          zeroed = true;
>      }
> -- 
> 2.6.2
> 

Apart from the cosmetic nits:

Reviewed-by: Fam Zheng <famz@redhat.com>