selftests/vm: dedup hugepage allocation logic

The code

	p = alloc_mapping();
	printf("Allocate huge page...");
	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
	fill_memory(p, 0, hpage_pmd_size);
	if (check_huge(p))
		success("OK");
	else
		fail("Fail");

Is repeated many times in different tests.  Add a helper, alloc_hpage()
to handle this.

Link: https://lkml.kernel.org/r/20220706235936.2197195-16-zokeefe@google.comSigned-off-by: Zach O'Keefe <zokeefe@google.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Chris Kennelly <ckennelly@google.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pavel Begunkov <asml.silence@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rongwei Wang <rongwei.wang@linux.alibaba.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Souptick Joarder (HPE)" <jrdr.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/vm/khugepaged.c

@@ -461,6 +461,25 @@ static void fill_memory(int *p, unsigned long start, unsigned long end)
 		p[i * page_size / sizeof(*p)] = i + 0xdead0000;
 }
 
+/*
+ * Returns pmd-mapped hugepage in VMA marked VM_HUGEPAGE, filled with
+ * validate_memory()'able contents.
+ */
+static void *alloc_hpage(void)
+{
+	void *p;
+
+	p = alloc_mapping();
+	printf("Allocate huge page...");
+	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
+	fill_memory(p, 0, hpage_pmd_size);
+	if (check_huge(p))
+		success("OK");
+	else
+		fail("Fail");
+	return p;
+}
+
 static void validate_memory(int *p, unsigned long start, unsigned long end)
 {
 	int i;
@@ -682,15 +701,7 @@ static void collapse_single_pte_entry_compound(struct collapse_context *c)
 {
 	void *p;
 
-	p = alloc_mapping();
-
-	printf("Allocate huge page...");
-	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
-	fill_memory(p, 0, hpage_pmd_size);
-	if (check_huge(p))
-		success("OK");
-	else
-		fail("Fail");
+	p = alloc_hpage();
 	madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE);
 
 	printf("Split huge page leaving single PTE mapping compound page...");
@@ -710,16 +721,7 @@ static void collapse_full_of_compound(struct collapse_context *c)
 {
 	void *p;
 
-	p = alloc_mapping();
-
-	printf("Allocate huge page...");
-	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
-	fill_memory(p, 0, hpage_pmd_size);
-	if (check_huge(p))
-		success("OK");
-	else
-		fail("Fail");
-
+	p = alloc_hpage();
 	printf("Split huge page leaving single PTE page table full of compound pages...");
 	madvise(p, page_size, MADV_NOHUGEPAGE);
 	madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE);
@@ -837,16 +839,7 @@ static void collapse_fork_compound(struct collapse_context *c)
 	int wstatus;
 	void *p;
 
-	p = alloc_mapping();
-
-	printf("Allocate huge page...");
-	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
-	fill_memory(p, 0, hpage_pmd_size);
-	if (check_huge(p))
-		success("OK");
-	else
-		fail("Fail");
-
+	p = alloc_hpage();
 	printf("Share huge page over fork()...");
 	if (!fork()) {
 		/* Do not touch settings on child exit */
@@ -896,16 +889,7 @@ static void collapse_max_ptes_shared(struct collapse_context *c)
 	int wstatus;
 	void *p;
 
-	p = alloc_mapping();
-
-	printf("Allocate huge page...");
-	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
-	fill_memory(p, 0, hpage_pmd_size);
-	if (check_huge(p))
-		success("OK");
-	else
-		fail("Fail");
-
+	p = alloc_hpage();
 	printf("Share huge page over fork()...");
 	if (!fork()) {
 		/* Do not touch settings on child exit */