Re: Add pg_buffercache_mark_dirty[_all] functions to the pg_buffercache

> I do not think that will be a problem but I can change it if the
> general consensus is towards this way. Also, if we change this for
> pg_buffercache_mark_dirty_* functions, I think we need to apply the
> same for the pg_buffercache_evict_* functions.

After some testing, bgwriter/checkpointer didn' blocks the mark buffer
dirty SQL. it's ok to use LWLockAcquire.

There is an extra line break after elog(ERROR, "bad buffer ID: %d", buf)
which can be removed.

Best regards,
Yuhang Qiu