qcow2: Factor out handle_dependencies()

}

/*

 * Allocates new clusters for the given guest_offset.

 *

 * At most *nb_clusters are allocated, and on return *nb_clusters is updated to

 * contain the number of clusters that have been allocated and are contiguous

 * in the image file.

 *

 * If *host_offset is non-zero, it specifies the offset in the image file at

 * which the new clusters must start. *nb_clusters can be 0 on return in this

 * case if the cluster at host_offset is already in use. If *host_offset is

 * zero, the clusters can be allocated anywhere in the image file.

 *

 * *host_offset is updated to contain the offset into the image file at which

 * the first allocated cluster starts.

 *

 * Return 0 on success and -errno in error cases. -EAGAIN means that the

 * function has been waiting for another request and the allocation must be

 * restarted, but the whole request should not be failed.

 * Check if there already is an AIO write request in flight which allocates

 * the same cluster. In this case we need to wait until the previous

 * request has completed and updated the L2 table accordingly.

 */

static int do_alloc_cluster_offset(BlockDriverState *bs, uint64_t guest_offset,

    uint64_t *host_offset, unsigned int *nb_clusters)

static int handle_dependencies(BlockDriverState *bs, uint64_t guest_offset,

    unsigned int *nb_clusters)

{

    BDRVQcowState *s = bs->opaque;

    QCowL2Meta *old_alloc;

    trace_qcow2_do_alloc_clusters_offset(qemu_coroutine_self(), guest_offset,

                                         *host_offset, *nb_clusters);

    /*

     * Check if there already is an AIO write request in flight which allocates

     * the same cluster. In this case we need to wait until the previous

     * request has completed and updated the L2 table accordingly.

     */

    QLIST_FOREACH(old_alloc, &s->cluster_allocs, next_in_flight) {

        uint64_t start = guest_offset >> s->cluster_bits;

        abort();

    }

    return 0;

}

/*

 * Allocates new clusters for the given guest_offset.

 *

 * At most *nb_clusters are allocated, and on return *nb_clusters is updated to

 * contain the number of clusters that have been allocated and are contiguous

 * in the image file.

 *

 * If *host_offset is non-zero, it specifies the offset in the image file at

 * which the new clusters must start. *nb_clusters can be 0 on return in this

 * case if the cluster at host_offset is already in use. If *host_offset is

 * zero, the clusters can be allocated anywhere in the image file.

 *

 * *host_offset is updated to contain the offset into the image file at which

 * the first allocated cluster starts.

 *

 * Return 0 on success and -errno in error cases. -EAGAIN means that the

 * function has been waiting for another request and the allocation must be

 * restarted, but the whole request should not be failed.

 */

static int do_alloc_cluster_offset(BlockDriverState *bs, uint64_t guest_offset,

    uint64_t *host_offset, unsigned int *nb_clusters)

{

    BDRVQcowState *s = bs->opaque;

    int ret;

    trace_qcow2_do_alloc_clusters_offset(qemu_coroutine_self(), guest_offset,

                                         *host_offset, *nb_clusters);

    ret = handle_dependencies(bs, guest_offset, nb_clusters);

    if (ret < 0) {

        return ret;

    }

    /* Allocate new clusters */

    trace_qcow2_cluster_alloc_phys(qemu_coroutine_self());

    if (*host_offset == 0) {

        *host_offset = cluster_offset;

        return 0;

    } else {

        int ret = qcow2_alloc_clusters_at(bs, *host_offset, *nb_clusters);

        ret = qcow2_alloc_clusters_at(bs, *host_offset, *nb_clusters);

        if (ret < 0) {

            return ret;

        }