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 <a...@linux-foundation.org>
Cc: Vlastimil Babka <vba...@suse.cz>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Mike Rapoport <r...@linux.vnet.ibm.com>
Cc: Mike Kravetz <mike.krav...@oracle.com>
Cc: Jason Gunthorpe <j...@ziepe.ca>
Cc: Dan Williams <dan.j.willi...@intel.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Michal Hocko <mho...@kernel.org>
Cc: Mark Rutland <mark.rutl...@arm.com>
Cc: Mark Brown <broo...@kernel.org>
Cc: Steven Price <steven.pr...@arm.com>
Cc: Ard Biesheuvel <ard.biesheu...@linaro.org>
Cc: Masahiro Yamada <yamada.masah...@socionext.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
Cc: Matthew Wilcox <wi...@infradead.org>
Cc: Sri Krishna chowdary <schowd...@nvidia.com>
Cc: Dave Hansen <dave.han...@intel.com>
Cc: Russell King - ARM Linux <li...@armlinux.org.uk>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Paul Mackerras <pau...@samba.org>
Cc: Martin Schwidefsky <schwidef...@de.ibm.com>
Cc: Heiko Carstens <heiko.carst...@de.ibm.com>
Cc: "David S. Miller" <da...@davemloft.net>
Cc: Vineet Gupta <vgu...@synopsys.com>
Cc: James Hogan <jho...@kernel.org>
Cc: Paul Burton <paul.bur...@mips.com>
Cc: Ralf Baechle <r...@linux-mips.org>
Cc: Kirill A. Shutemov <kir...@shutemov.name>
Cc: Gerald Schaefer <gerald.schae...@de.ibm.com>
Cc: Christophe Leroy <christophe.le...@c-s.fr>
Cc: David Rientjes <rient...@google.com>
Cc: Andrea Arcangeli <aarca...@redhat.com>
Cc: Oscar Salvador <osalva...@suse.de>
Cc: Mel Gorman <mgor...@techsingularity.net>
Cc: linux-snps-arc@lists.infradead.org
Cc: linux-m...@vger.kernel.org
Cc: linux-arm-ker...@lists.infradead.org
Cc: linux-i...@vger.kernel.org
Cc: linuxppc-...@lists.ozlabs.org
Cc: linux-s...@vger.kernel.org
Cc: linux...@vger.kernel.org
Cc: sparcli...@vger.kernel.org
Cc: x...@kernel.org
Cc: linux-ker...@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khand...@arm.com>
---
 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);
-
-               if (page_zone(page) != z)
-                       return false;
-
-               if (PageReserved(page))
-                       return false;
-
-               if (page_count(page) > 0)
-                       return false;
-
-               if (PageHuge(page))
-                       return false;
-       }
-
-       return true;
-}
-
-static bool zone_spans_last_pfn(const struct zone *zone,
-                       unsigned long start_pfn, unsigned long nr_pages)
-{
-       unsigned long last_pfn = start_pfn + nr_pages - 1;
-       return zone_spans_pfn(zone, last_pfn);
-}
-
 static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
                int nid, nodemask_t *nodemask)
 {
        unsigned int order = huge_page_order(h);
-       unsigned long nr_pages = 1 << order;
-       unsigned long ret, pfn, flags;
-       struct zonelist *zonelist;
-       struct zone *zone;
-       struct zoneref *z;
-
-       zonelist = node_zonelist(nid, gfp_mask);
-       for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(gfp_mask), 
nodemask) {
-               spin_lock_irqsave(&zone->lock, flags);
 
-               pfn = ALIGN(zone->zone_start_pfn, nr_pages);
-               while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
-                       if (pfn_range_valid_gigantic(zone, pfn, nr_pages)) {
-                               /*
-                                * We release the zone lock here because
-                                * alloc_contig_range() will also lock the zone
-                                * at some point. If there's an allocation
-                                * spinning on this lock, it may win the race
-                                * and cause alloc_contig_range() to fail...
-                                */
-                               spin_unlock_irqrestore(&zone->lock, flags);
-                               ret = __alloc_gigantic_page(pfn, nr_pages, 
gfp_mask);
-                               if (!ret)
-                                       return pfn_to_page(pfn);
-                               spin_lock_irqsave(&zone->lock, flags);
-                       }
-                       pfn += nr_pages;
-               }
-
-               spin_unlock_irqrestore(&zone->lock, flags);
-       }
-
-       return NULL;
+       return alloc_gigantic_page_order(order, gfp_mask, nid, nodemask);
 }
 
 static void prep_new_huge_page(struct hstate *h, struct page *page, int nid);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6ab8eb670fd3..0f67367213c6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8497,6 +8497,104 @@ int alloc_contig_range(unsigned long start, unsigned 
long end,
                                pfn_max_align_up(end), migratetype);
        return ret;
 }
+
+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);
+
+               if (page_zone(page) != z)
+                       return false;
+
+               if (PageReserved(page))
+                       return false;
+
+               if (page_count(page) > 0)
+                       return false;
+
+               if (PageHuge(page))
+                       return false;
+       }
+       return true;
+}
+
+static bool zone_spans_last_pfn(const struct zone *zone,
+                               unsigned long start_pfn, unsigned long nr_pages)
+{
+       unsigned long last_pfn = start_pfn + nr_pages - 1;
+
+       return zone_spans_pfn(zone, last_pfn);
+}
+
+/**
+ * alloc_gigantic_page_order() -- tries to allocate given order of pages
+ * @order:     allocation order (greater than MAX_ORDER)
+ * @gfp_mask:  GFP mask to use during compaction
+ * @nid:       allocation node
+ * @nodemask:  allocation nodemask
+ *
+ * This routine is an wrapper around alloc_contig_range() which scans over
+ * all zones on an applicable zonelist to find a contiguous pfn range which
+ * can the be allocated with alloc_contig_range(). This routine is intended
+ * to be used for allocations greater than MAX_ORDER.
+ *
+ * Return: page on success or NULL on failure. On success a memory block
+ * of 'order' starting with 'page' has been allocated successfully. Memory
+ * allocated here needs to be freed with free_contig_range().
+ */
+struct page *alloc_gigantic_page_order(unsigned int order, gfp_t gfp_mask,
+                                      int nid, nodemask_t *nodemask)
+{
+       unsigned long nr_pages = 1 << order;
+       unsigned long ret, pfn, flags;
+       struct zonelist *zonelist;
+       struct zone *zone;
+       struct zoneref *z;
+
+       zonelist = node_zonelist(nid, gfp_mask);
+       for_each_zone_zonelist_nodemask(zone, z, zonelist,
+                                       gfp_zone(gfp_mask), nodemask) {
+               spin_lock_irqsave(&zone->lock, flags);
+
+               pfn = ALIGN(zone->zone_start_pfn, nr_pages);
+               while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
+                       if (pfn_range_valid_gigantic(zone, pfn, nr_pages)) {
+                               /*
+                                * We release the zone lock here because
+                                * alloc_contig_range() will also lock the zone
+                                * at some point. If there's an allocation
+                                * spinning on this lock, it may win the race
+                                * and cause alloc_contig_range() to fail...
+                                */
+                               spin_unlock_irqrestore(&zone->lock, flags);
+                               ret = __alloc_gigantic_page(pfn, nr_pages,
+                                                       gfp_mask);
+                               if (!ret)
+                                       return pfn_to_page(pfn);
+                               spin_lock_irqsave(&zone->lock, flags);
+                       }
+                       pfn += nr_pages;
+               }
+               spin_unlock_irqrestore(&zone->lock, flags);
+       }
+       return NULL;
+}
 #endif /* CONFIG_CONTIG_ALLOC */
 
 void free_contig_range(unsigned long pfn, unsigned int nr_pages)
-- 
2.20.1


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