diff options
| -rw-r--r-- | block/qcow2-cluster.c | 44 |
1 files changed, 23 insertions, 21 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index b04bfafd65..a59fb3493c 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -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; - l1_bits = s->l2_bits + s->cluster_bits; - - /* compute how many bytes there are between the offset and - * the end of the l1 entry - */ + offset_in_cluster = offset_into_cluster(s, offset); + bytes_needed = (uint64_t) bytes + offset_in_cluster; - nb_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1)); - - /* compute the number of available sectors */ + l1_bits = s->l2_bits + s->cluster_bits; - nb_available = (nb_available >> 9) + index_in_cluster; + /* 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; - 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; |