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qcow2: Work with bytes in qcow2_get_cluster_offset()

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This patch changes the units that qcow2_get_cluster_offset() uses
internally, without touching the interface just yet. This will be done
in another patch.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Kevin Wolf 2016-05-31 16:41:09 +02:00
parent a66370b08d
commit b2f65d6b02
1 changed files with 23 additions and 21 deletions
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44
block/qcow2-cluster.c
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@ -482,29 +482,28 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
unsigned int l2_index;
uint64_t l1_index, l2_offset, *l2_table;
int l1_bits, c;
unsigned int index_in_cluster, nb_clusters;
uint64_t nb_available, nb_needed;
unsigned int offset_in_cluster, nb_clusters;
uint64_t bytes_available, bytes_needed;
int ret;
unsigned int bytes;
index_in_cluster = (offset >> 9) & (s->cluster_sectors - 1);
nb_needed = *num + index_in_cluster;
assert(*num <= BDRV_REQUEST_MAX_SECTORS);
bytes = *num * BDRV_SECTOR_SIZE;
offset_in_cluster = offset_into_cluster(s, offset);
bytes_needed = (uint64_t) bytes + offset_in_cluster;
l1_bits = s->l2_bits + s->cluster_bits;
/* compute how many bytes there are between the offset and
* the end of the l1 entry
*/
/* compute how many bytes there are between the start of the cluster
* containing offset and the end of the l1 entry */
bytes_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1))
+ offset_in_cluster;
nb_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1));
/* compute the number of available sectors */
nb_available = (nb_available >> 9) + index_in_cluster;
if (nb_needed > nb_available) {
nb_needed = nb_available;
if (bytes_needed > bytes_available) {
bytes_needed = bytes_available;
}
assert(nb_needed <= INT_MAX);
assert(bytes_needed <= INT_MAX);
*cluster_offset = 0;
@ -542,7 +541,7 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
*cluster_offset = be64_to_cpu(l2_table[l2_index]);
/* nb_needed <= INT_MAX, thus nb_clusters <= INT_MAX, too */
nb_clusters = size_to_clusters(s, nb_needed << 9);
nb_clusters = size_to_clusters(s, bytes_needed);
ret = qcow2_get_cluster_type(*cluster_offset);
switch (ret) {
@ -589,13 +588,16 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
nb_available = (c * s->cluster_sectors);
bytes_available = (c * s->cluster_size);
out:
if (nb_available > nb_needed)
nb_available = nb_needed;
if (bytes_available > bytes_needed) {
bytes_available = bytes_needed;
}
*num = nb_available - index_in_cluster;
bytes = bytes_available - offset_in_cluster;
assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
*num = bytes >> BDRV_SECTOR_BITS;
return ret;