selftests/mm: remove virtual_address_range test

selftests/mm: remove virtual_address_range test

This self test is asserting internal implementation details and is highly
vulnerable to internal kernel changes as a result.

It is currently failing locally from at least v6.17, and it seems that it
may have been failing for longer in many configurations/hardware as it
skips if e.g.  CONFIG_ANON_VMA_NAME is not specified.

With these skips and the fact that run_vmtests.sh won't run the tests in
certain configurations it is likely we have simply missed this test being
broken in CI for a long while.

I have tried multiple versions of these tests and am unable to find a
working bisect as previous versions of the test fail also.

The tests are essentially mmap()'ing a series of mappings with no hint and
asserting what the get_unmapped_area*() functions will come up with, with
seemingly few checks for what other mappings may already be in place.

It then appears to be mmap()'ing with a hint, and making a series of
similar assertions about the internal implementation details of the
hinting logic.

Commit 0ef3783d7558 ("selftests/mm: add support to test 4PB VA on PPC64"),
commit 3bd6137220bb ("selftests/mm: virtual_address_range: avoid reading
from VM_IO mappings"), and especially commit a005145b9c96 ("selftests/mm:
virtual_address_range: mmap() without PROT_WRITE") are good examples of
the whack-a-mole nature of maintaining this test.

The last commit there being particularly pertinent as it was accounting
for an internal implementation detail change that really should have no
bearing on self-tests, that is commit e93d2521b27f ("x86/vdso: Split
virtual clock pages into dedicated mapping").

The purpose of the mm self-tests are to assert attributes about the API
exposed to users, and to ensure that expectations are met.

This test is emphatically not doing this, rather making a series of
assumptions about internal implementation details and asserting them.

It therefore, sadly, seems that the best course is to remove this test
altogether.

Link: https://lkml.kernel.org/r/20260116132053.857887-1-lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: SeongJae Park <sj@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>