Am 06.02.2015 um 16:31 hat Eric Blake geschrieben: > On 02/06/2015 08:27 AM, Eric Blake wrote: > > >> > >> - /* The cluster refcount was incremented, either by > >> qcow2_alloc_clusters() > >> - * or explicitly by qcow2_update_cluster_refcount(). Refcount blocks > >> must > >> - * be flushed before the caller's L2 table updates. > >> - */ > >> + assert(offset); > >> + ret = update_refcount(bs, offset, size, 1, QCOW2_DISCARD_NEVER); > > > > Case 1: This incremented the new cluster. Good > > Case 2: This incremented the old cluster. Good > > Case 3: This incremented the new cluster. Good > > Case 4: This incremented the old cluster. But the new cluster remains at > > refcount 0. BAD. > > Wait. Maybe I'm confused. You are requesting an update_refcount() > across size bytes, and given the offset, that means that the code will > round up to cover BOTH clusters in one call. Does update_refcount() > properly increment from [ 1, 0 ] to [ 2, 1 ] when given a 2-cluster > size (when offset, size is rounded up to cluster boundaries)? If so, > then there is no bug after all.
Yes, this is what it should be doing. Letting one update_refcount() call (more or less) atomically increment both refcounts was the whole point of my suggestion anyway because that is what enables the simplification. Kevin
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