Re: [Qemu-devel] [PATCH 2/4] block: image fragmentation statistics for qed

[Stefan Hajnoczi]

On Wed, Mar 7, 2012 at 9:22 AM, Dong Xu Wang <address@hidden> wrote:
> +    for (i = 0; i < table_noffsets; i++) {
> +        l2_offset = s->l1_table->offsets[i];
> +        if (l2_offset == 0) {

if (qed_offset_is_unalloc_cluster(l2_offset)) {

> +            continue;
> +        }
> +        ret = bdrv_pread(bs->file, l2_offset, table, size);
> +        if (ret < 0) {
> +            qemu_vfree(table);
> +            return ret;
> +        }
> +        for (j = 0; j < size/sizeof(uint64_t); j++) {
> +            uint64_t *offset = (uint64_t *)(table + j);

No need to cast, table is already uint64_t*.

Since you don't write to the offset, I would just do:

uint64_t offset = table[j];

> +            if (*offset < cluster_size) {
> +                continue;
> +            }

if (!qed_check_cluster_offset(s, offset)) {
    continue;
}

We will skip unallocated clusters and zero clusters.

Stefan