/proc/*/maps broken on nommu

[Max Filippov]

Hello,

As of v6.5 cat /proc/*/maps produces empty output on nommu xtensa systems.
Bisection points to the commit 0c563f148043 ("proc: remove VMA rbtree
use from nommu").
It looks like the issue may be not in the m_start (where find_vma(mm,
addr) returns
NULL), but in the nommu version of find_vma itself. I've tried replacing nommu
find_vma implementation with an implementation of the MMU version and it
fixes the /proc/*/maps output. Kind of (it works as expected on one of
my systems,
but consistently locks up on the other).

Any suggestions of what might be wrong/how to fix it properly?

-- 
Thanks.
-- Max