selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage

It's good to have basic unit test coverage of the new FOLL_PIN behavior.
Fortunately, the gup_benchmark unit test is extremely fast (a few
milliseconds), so adding it the the run_vmtests suite is going to cause no
noticeable change in running time.

So, add two new invocations to run_vmtests:

1) Run gup_benchmark with normal get_user_pages().

2) Run gup_benchmark with pin_user_pages().  This is much like the
   first call, except that it sets FOLL_PIN.

Running these two in quick succession also provide a visual comparison of
the running times, which is convenient.

The new invocations are fairly early in the run_vmtests script, because
with test suites, it's usually preferable to put the shorter, faster tests
first, all other things being equal.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/20200211001536.1027652-11-jhubbard@nvidia.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>