It makes a lot of sense to make TMPFS a userspace application, so that it would be possible to kill it in case it overcommits memory (see bug 201673) and to understand real memory pressure using top/ps.
Right now, both `top` and `free` don't take the RAM consumed by TMPFS into consideration (and I presume the kernel itself) which leads to all sorts of bad situations.
This looks like a very serious bug probably needs to be fixed.
What do you think Linus?
AFAIK, this has been changed/fixed and now reported as shared memory.