On 02/10/2015 01:28 PM, Max Reitz wrote: > Refcounts can theoretically be of type uint64_t; in order to be able to > represent the full range, qcow2_get_refcount() cannot use a single > variable to represent both all refcount values and also keep some values > reserved for errors. > > One solution would be to add an Error pointer parameter to > qcow2_get_refcount(); however, no caller could (currently) pass that > error message, so it would have to be emitted immediately and be > passed to the next caller by returning -EIO or something similar. > Therefore, an Error parameter does not offer any advantages here. > > The solution applied by this patch is simpler to use. Because no caller > would be able to pass the error message, they would have to print it and > free it, whereas with this patch the caller only needs to pass the > returned integer (which is often a no-op from the code perspective, > because that integer will be stored in a variable "ret" which will be > returned by the fail path of many callers). > > Signed-off-by: Max Reitz > --- > block/qcow2-cluster.c | 8 ++--- > block/qcow2-refcount.c | 86 +++++++++++++++++++++++++++----------------------- > block/qcow2.h | 3 +- > 3 files changed, 53 insertions(+), 44 deletions(-) > > @@ -744,10 +749,9 @@ int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset, > /* Check how many clusters there are free */ > cluster_index = offset >> s->cluster_bits; > for(i = 0; i < nb_clusters; i++) { > - refcount = qcow2_get_refcount(bs, cluster_index++); Worth fixing the spacing after 'for' while touching here? (might even already happen later in the series). But not important enough for a respin, and I won't even care if a maintainer doesn't fold it in. Reviewed-by: Eric Blake -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org