SSE and compression wrap the payload so its length is unknown and
advertise HashReader::SIZE_PRESERVE_LAYER (-1). Every layer preserved
that sentinel except create_bitrot_writer, which clamped it to 0 before
calling DiskAPI::create_file. RemoteDisk forwards that size verbatim in
the put_file_stream query, so remote peers were told the body was empty.
Since the authenticated put-file trailer (#5868) the receiver used the
declared size to split body from trailer, turning the clamp into a fatal
"auth trailer has trailing data" failure for every SSE PUT on multi-node
deployments (rc.2). #6320 relaxed the receiver to only trust size > 0;
this change fixes the sender so the sentinel survives end to end and the
wire no longer conflates empty objects with unknown-length streams.
Refs #6331
唐小鸭
a3c812527f