hugepage: mention libhugetlbfs in doc

Explicitly mention/recommend using the libhugetlbfs test cases when
changing related kernel code. Developers that are unaware of the project
can easily miss this and introduce potential regressions that may or may
not be caught by community review.

Also do some cleanups that make the document visually easier to view at a
first glance.

Signed-off-by: Davidlohr Bueso <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/vm/hugetlbpage.txt

···
 
 
 Interaction of Task Memory Policy with Huge Page Allocation/Freeing
+===================================================================
 
 Whether huge pages are allocated and freed via the /proc interface or
 the /sysfs interface using the nr_hugepages_mempolicy attribute, the NUMA
···
    of huge pages over all on-lines nodes with memory.
 
 Per Node Hugepages Attributes
+=============================
 
 A subset of the contents of the root huge page control directory in sysfs,
 described above, will be replicated under each the system device of each
···
 
 
 Using Huge Pages
+================
 
 If the user applications are going to request huge pages using mmap system
 call, then it is required that system administrator mount a file system of
···
 without MAP_HUGETLB.  For an example of how to use mmap with MAP_HUGETLB see
 map_hugetlb.c.
 
-*******************************************************************
+Examples
+========
 
-/*
- * map_hugetlb: see tools/testing/selftests/vm/map_hugetlb.c
- */
+1) map_hugetlb: see tools/testing/selftests/vm/map_hugetlb.c
 
-*******************************************************************
+2) hugepage-shm:  see tools/testing/selftests/vm/hugepage-shm.c
 
-/*
- * hugepage-shm:  see tools/testing/selftests/vm/hugepage-shm.c
- */
+3) hugepage-mmap:  see tools/testing/selftests/vm/hugepage-mmap.c
 
-*******************************************************************
-
-/*
- * hugepage-mmap:  see tools/testing/selftests/vm/hugepage-mmap.c
- */
+4) The libhugetlbfs (http://libhugetlbfs.sourceforge.net) library provides a
+   wide range of userspace tools to help with huge page usability, environment
+   setup, and control. Furthermore it provides useful test cases that should be
+   used when modifying code to ensure no regressions are introduced.