Re: [Qemu-devel] [PATCH v2] qcow2: add update refcount table realization for update_refcount

[Benoît Canet]

The Monday 01 Sep 2014 à 18:52:48 (+0800), Jun Li wrote :
> When every item of refcount block is NULL, free refcount block and reset the
> corresponding item of refcount table with NULL.
> 
> Signed-off-by: Jun Li <address@hidden>
> ---
> 
> The v2 do following change to modify some potential issue.
> 
>              +------- Here should start from "0".
>              |
>     for (k = 0; k < refcount_block_entries; k++) {
>         if (refcount_block[k] != cpu_to_be16(0)) {
>         ...                |                 |
>         }                  |                 |
>     }                      |                 +---- Using "0" is more safe.
>                            |
>                            +-------- This should be "k" not "++k".
> ---
>  block/qcow2-refcount.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> index 43665b8..63f36e6 100644
> --- a/block/qcow2-refcount.c
> +++ b/block/qcow2-refcount.c
> @@ -586,6 +586,37 @@ static int QEMU_WARN_UNUSED_RESULT 
> update_refcount(BlockDriverState *bs,
>          if (refcount == 0 && s->discard_passthrough[type]) {
>              update_refcount_discard(bs, cluster_offset, s->cluster_size);
>          }
> +
> +        /* When refcount block is NULL, update refcount table */
> +        if (block_index == 0) {
> +            int k = block_index;
> +            int refcount_block_entries = s->cluster_size / sizeof(uint16_t);
> +            for (k = 0; k < refcount_block_entries; k++) {
> +                if (refcount_block[k] != cpu_to_be16(0)) {
> +                    break;
> +                }
> +            }
> +
> +            if (k == refcount_block_entries) {
> +                qemu_vfree(refcount_block);
> +                /* update refcount table */
> +                unsigned int refcount_table_index;
> +                uint64_t data64 = cpu_to_be64(0);
> +                refcount_table_index = cluster_index >> (s->cluster_bits -
> +                                       REFCOUNT_SHIFT);
> +                ret = bdrv_pwrite_sync(bs->file,
> +                                       s->refcount_table_offset +
> +                                       refcount_table_index *
> +                                       sizeof(uint64_t),
> +                                       &data64, sizeof(data64));
> +                if (ret < 0) {
> +                    goto fail;
> +                }
> +

> +                s->refcount_table[refcount_table_index] = data64;

Shouldn't the in memory version be be in cpu order ? like
        s->refcount_table[refcount_table_index] = 0;

Best regards

Benoît 
> +
> +            }
> +        }
>      }
>  
>      ret = 0;
> -- 
> 1.9.3
> 
>