This patch introduces a further check to compress_chunk_impl and
decompress_chunk_impl. After all locks are acquired, a check is made
to see if the chunk is still (un-)compressed. If the chunk was
(de-)compressed while waiting for the locks, the (de-)compression
operation is stopped.
In addition, the chunk locks in decompress_chunk_impl
are upgraded to AccessExclusiveLock to ensure the chunk is not deleted
while other transactions are using it.
Fixes: #4480
