> > while vndthread is working on behalf of the pagedaemon here,
> > it is not a pagedaemon.  so it can't get special treatment for pagedaemon
> > from buffer cache etc and can deadlock.
> 
> In my case it is definitely not working on behalf of the pagedaemon.

did you have plenty of free memory?  it wasn't clear from the PR.

you said "separate pool for nested I/O buffers" worked.
it made me think you were low of memory, given that getiobuf() is not
related to buffer cache watermarks.

YAMAMOTO Takashi