selftests: expanding more mlock selftest

selftests: expanding more mlock selftest

This patch will randomly perform mlock/mlock2 on a given memory region,
and verify the RLIMIT_MEMLOCK limitation works properly.

Suggested-by: David Rientjes <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Simon Guo <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Eric B Munson <[email protected]>
Cc: Simon Guo <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Alexey Klimov <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Thierry Reding <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>