int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size) { BDRVQcowState *s = bs->opaque; int64_t offset; size_t free_in_cluster; int ret; BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_BYTES); assert(size > 0 && size <= s->cluster_size); assert(!s->free_byte_offset || offset_into_cluster(s, s->free_byte_offset)); offset = s->free_byte_offset; if (offset) { uint64_t refcount; ret = qcow2_get_refcount(bs, offset >> s->cluster_bits, &refcount); if (ret < 0) { return ret; } if (refcount == s->refcount_max) { offset = 0; } } free_in_cluster = s->cluster_size - offset_into_cluster(s, offset); if (!offset || free_in_cluster < size) { int64_t new_cluster = alloc_clusters_noref(bs, s->cluster_size); if (new_cluster < 0) { return new_cluster; } if (!offset || ROUND_UP(offset, s->cluster_size) != new_cluster) { offset = new_cluster; } } assert(offset); ret = update_refcount(bs, offset, size, 1, false, QCOW2_DISCARD_NEVER); if (ret < 0) { return ret; } /* The cluster refcount was incremented; refcount blocks must be flushed * before the caller's L2 table updates. */ qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache); s->free_byte_offset = offset + size; if (!offset_into_cluster(s, s->free_byte_offset)) { s->free_byte_offset = 0; } return offset; }