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qcow2: Factor out count_cow_clusters 

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
This commit is contained in:
Kevin Wolf 2012-03-02 19:27:53 +01:00
parent 6cc2a4157b
commit bf319ece56
1 changed files with 36 additions and 19 deletions
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55
block/qcow2-cluster.c
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@ -676,6 +676,41 @@ err:
return ret;
}
/*
* Returns the number of contiguous clusters that can be used for an allocating
* write, but require COW to be performed (this includes yet unallocated space,
* which must copy from the backing file)
*/
static int count_cow_clusters(BDRVQcowState *s, int nb_clusters,
uint64_t *l2_table, int l2_index)
{
int i = 0;
uint64_t cluster_offset;
while (i < nb_clusters) {
i += count_contiguous_clusters(nb_clusters - i, s->cluster_size,
&l2_table[l2_index], i, 0);
if ((i >= nb_clusters) || be64_to_cpu(l2_table[l2_index + i])) {
break;
}
i += count_contiguous_free_clusters(nb_clusters - i,
&l2_table[l2_index + i]);
if (i >= nb_clusters) {
break;
}
cluster_offset = be64_to_cpu(l2_table[l2_index + i]);
if ((cluster_offset & QCOW_OFLAG_COPIED) ||
(cluster_offset & QCOW_OFLAG_COMPRESSED))
break;
}
assert(i <= nb_clusters);
return i;
}
/*
* alloc_cluster_offset
*
@ -739,25 +774,7 @@ again:
/* how many available clusters ? */
while (i < nb_clusters) {
i += count_contiguous_clusters(nb_clusters - i, s->cluster_size,
&l2_table[l2_index], i, 0);
if ((i >= nb_clusters) || be64_to_cpu(l2_table[l2_index + i])) {
break;
}
i += count_contiguous_free_clusters(nb_clusters - i,
&l2_table[l2_index + i]);
if (i >= nb_clusters) {
break;
}
cluster_offset = be64_to_cpu(l2_table[l2_index + i]);
if ((cluster_offset & QCOW_OFLAG_COPIED) ||
(cluster_offset & QCOW_OFLAG_COMPRESSED))
break;
}
i = count_cow_clusters(s, nb_clusters, l2_table, l2_index);
assert(i <= nb_clusters);
nb_clusters = i;