On Tue, 29 Mar 2016, Arnd Bergmann wrote:

How do we do it then? Should we just define __USE_FILE_OFFSET64
unconditionally for all new 32-bit architectures and leave the
code dealing with 32-bit off_t/ino_t in place but unreachable, to
minimize the differences?

Defining __USE_FILE_OFFSET64 unconditionally would prevent glibc from 
building (see: how the patches a while back prototyping changing the 
default had to disable the change when glibc itself is built).  A change 
in the default, though desired (someone needs to pick up those patches 
together with the analysis done of possible impact on distributions), 
should not be tied to a new port, and would need to be discussed 
thoroughly on libc-alpha.

Or should all the obsolete types be defined the same way as their
replacements so we have 64-bit __OFF_T_TYPE/__INO_T_TYPE
and use the same binary implementation regardless of FILE_OFFSET_BITS?

I think so (along with using wordsize-64 sysdeps directories as far as 
possible, like x32 does).  But design questions for a glibc port really 
belong on libc-alpha to get any sort of community consensus.

-- 
Joseph S. Myers
joseph at codesourcery.com