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qcow2: Add qcow2_alloc_clusters_at() 

This function allows to allocate clusters at a given offset in the image
file. This is useful if you want to allocate the second part of an area
that must be contiguous.

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 19:35:58 +01:00
parent bf319ece56
commit 256900b16b
2 changed files with 30 additions and 0 deletions
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28
block/qcow2-refcount.c
View File

@ -582,6 +582,34 @@ int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size)
return offset;
}
int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
int nb_clusters)
{
BDRVQcowState *s = bs->opaque;
uint64_t cluster_index;
int i, refcount, ret;
/* Check how many clusters there are free */
cluster_index = offset >> s->cluster_bits;
for(i = 0; i < nb_clusters; i++) {
refcount = get_refcount(bs, cluster_index++);
if (refcount < 0) {
return refcount;
} else if (refcount != 0) {
break;
}
}
/* And then allocate them */
ret = update_refcount(bs, offset, i << s->cluster_bits, 1);
if (ret < 0) {
return ret;
}
return i;
}
/* only used to allocate compressed sectors. We try to allocate
contiguous sectors. size must be <= cluster_size */
int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)

2
block/qcow2.h
View File

@ -193,6 +193,8 @@ int qcow2_refcount_init(BlockDriverState *bs);
void qcow2_refcount_close(BlockDriverState *bs);
int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size);
int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
int nb_clusters);
int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size);
void qcow2_free_clusters(BlockDriverState *bs,
int64_t offset, int64_t size);