alloc_gigantic_page() implements an allocation method where it scans over
various zones looking for a large contiguous memory block which could not
have been allocated through the buddy allocator. A subsequent patch which
tests arch page table helpers needs such a method to allocate PUD_SIZE
sized memory block. In the future such methods might have other use cases
as well. So alloc_gigantic_page() has been split carving out actual memory
allocation method and made available via new alloc_gigantic_page_order()
which is wrapped under CONFIG_CONTIG_ALLOC.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <redacted>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Thomas Gleixner <redacted>
Cc: Mike Rapoport <redacted>
Cc: Mike Kravetz <redacted>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Dan Williams <redacted>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Steven Price <Steven.Price@arm.com>
Cc: Ard Biesheuvel <redacted>
Cc: Masahiro Yamada <redacted>
Cc: Kees Cook <redacted>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sri Krishna chowdary <redacted>
Cc: Dave Hansen <redacted>
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <redacted>
Cc: Martin Schwidefsky <redacted>
Cc: Heiko Carstens <redacted>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Vineet Gupta <redacted>
Cc: James Hogan <jhogan@kernel.org>
Cc: Paul Burton <redacted>
Cc: Ralf Baechle <redacted>
Cc: Kirill A. Shutemov <redacted>
Cc: Gerald Schaefer <redacted>
Cc: Christophe Leroy <redacted>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrea Arcangeli <redacted>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Mel Gorman <redacted>
Cc: linux-snps-arc@lists.infradead.org
Cc: linux-mips@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-ia64@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: sparclinux@vger.kernel.org
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <redacted>
---
  include/linux/gfp.h |  3 ++
  mm/hugetlb.c        | 76 +----------------------------------
  mm/page_alloc.c     | 98 +++++++++++++++++++++++++++++++++++++++++++++
  3 files changed, 102 insertions(+), 75 deletions(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index fb07b503dc45..379ad23437d1 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h

@@ -589,6 +589,9 @@ static inline bool pm_suspended_storage(void)
  /* The below functions must be run on a range from a single zone. */
  extern int alloc_contig_range(unsigned long start, unsigned long end,
  			      unsigned migratetype, gfp_t gfp_mask);
+extern struct page *alloc_gigantic_page_order(unsigned int order,
+					      gfp_t gfp_mask, int nid,
+					      nodemask_t *nodemask);
  #endif
  void free_contig_range(unsigned long pfn, unsigned int nr_pages);
  

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 977f9a323a7a..d199556a4a2c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c

@@ -1023,86 +1023,12 @@ static void free_gigantic_page(struct page *page, unsigned int order)
  }
  
  #ifdef CONFIG_CONTIG_ALLOC
-static int __alloc_gigantic_page(unsigned long start_pfn,
-				unsigned long nr_pages, gfp_t gfp_mask)
-{
-	unsigned long end_pfn = start_pfn + nr_pages;
-	return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE,
-				  gfp_mask);
-}
-
-static bool pfn_range_valid_gigantic(struct zone *z,
-			unsigned long start_pfn, unsigned long nr_pages)
-{
-	unsigned long i, end_pfn = start_pfn + nr_pages;
-	struct page *page;
-
-	for (i = start_pfn; i < end_pfn; i++) {
-		if (!pfn_valid(i))
-			return false;
-
-		page = pfn_to_page(i);