read errors mapping "/path/file": No data available (in version 3.0.6)

[Carlos Carvalho]

Got this in the log:

WARNING: path/file failed verification -- update discarded (will try again).
rsync: read errors mapping "/path/file": No data available (61)

The first line is rare but understandable. It's the second one that I
find strange. What does "no data available" mean? The file exists on
the origin (and on the destination). The second attempt should have
worked normally. This happened with --link-dest.