I have my portage DISTDIR automounted from an nfs server at /misc/distfiles; /usr/portage/distfiles is a symlink, and DISTDIR is not explicitly set. This configuration worked fine on all versions of portage I have used for some years, and worked with 22.214.171.124. Since upgrading to 2.2.1, portage will not use the automounted DISTDIR.
Steps to Reproduce:
1. Configure portage as described
2. emerge gimp
>>> Emerging (1 of 1) media-gfx/gimp-2.8.6
!!! Directory Not Found: DISTDIR='/misc/distfiles'
!!! Fetching will fail!
!!! No write access to '/misc/distfiles'
!!! statvfs('/misc/distfiles'): [Errno 2] No such file or directory: '/misc/distfiles'
!!! File gimp-2.8.6.tar.bz2 isn't fetched but unable to get it.
* Fetch failed for 'media-gfx/gimp-2.8.6', Log file:
normal emerge output
I suspect that what's going on is that portage is using stat() to test whether /misc/distfiles exists, and then using mkdir() to open it if not. That's incorrect, as you shouldn't be mkdir()ing in a directory that is mounted with -t autofs (like /misc).
Here is the /proc/mounts line for /misc on my system:
/etc/autofs/auto.misc /misc autofs rw,relatime,fd=6,pgrp=28483,timeout=300,minproto=5,maxproto=5,indirect 0 0