Hi hackers,
there are a very long discuss about TDE, and we agreed on that if the
temporary file I/O can be aligned to some fixed size, it will be easier
to use some kind of encryption algorithm.
discuss:
https://www.postgresql.org/message-id/20211025155814.GD20998%40tamriel.snowman.net
This patch adjust file->curOffset and file->pos before the real IO to
ensure the start offset is aligned.