[PATCH V4 1/2] mm/hugetlb: Make alloc_gigantic_page() available for general use

[Anshuman Khandual]

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().

Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>
Cc: Steven Price <Steven.Price@xxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Sri Krishna chowdary <schowdary@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Cc: James Hogan <jhogan@xxxxxxxxxx>
Cc: Paul Burton <paul.burton@xxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxx>
Cc: linux-snps-arc@xxxxxxxxxxxxxxxxxxx
Cc: linux-mips@xxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-ia64@xxxxxxxxxxxxxxx
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Cc: linux-s390@xxxxxxxxxxxxxxx
Cc: linux-sh@xxxxxxxxxxxxxxx
Cc: sparclinux@xxxxxxxxxxxxxxx
Cc: x86@xxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
 include/linux/hugetlb.h |  9 +++++++++
 mm/hugetlb.c            | 24 ++++++++++++++++++++++--
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 53fc34f930d0..cc50d5ad4885 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -299,6 +299,9 @@ static inline bool is_file_hugepages(struct file *file)
 }
 
 
+struct page *
+alloc_gigantic_page_order(unsigned int order, gfp_t gfp_mask,
+			  int nid, nodemask_t *nodemask);
 #else /* !CONFIG_HUGETLBFS */
 
 #define is_file_hugepages(file)			false
@@ -310,6 +313,12 @@ hugetlb_file_setup(const char *name, size_t size, vm_flags_t acctflag,
 	return ERR_PTR(-ENOSYS);
 }
 
+static inline struct page *
+alloc_gigantic_page_order(unsigned int order, gfp_t gfp_mask,
+			  int nid, nodemask_t *nodemask)
+{
+	return NULL;
+}
 #endif /* !CONFIG_HUGETLBFS */
 
 #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ef37c85423a5..3fb81252f52b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1112,10 +1112,9 @@ static bool zone_spans_last_pfn(const struct zone *zone,
 	return zone_spans_pfn(zone, last_pfn);
 }
 
-static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
+struct page *alloc_gigantic_page_order(unsigned int order, 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;
@@ -1151,6 +1150,14 @@ static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
 	return NULL;
 }
 
+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);
+
+	return alloc_gigantic_page_order(order, gfp_mask, nid, nodemask);
+}
+
 static void prep_new_huge_page(struct hstate *h, struct page *page, int nid);
 static void prep_compound_gigantic_page(struct page *page, unsigned int order);
 #else /* !CONFIG_CONTIG_ALLOC */
@@ -1159,6 +1166,12 @@ static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
 {
 	return NULL;
 }
+
+struct page *alloc_gigantic_page_order(unsigned int order, gfp_t gfp_mask,
+				       int nid, nodemask_t *nodemask)
+{
+	return NULL;
+}
 #endif /* CONFIG_CONTIG_ALLOC */
 
 #else /* !CONFIG_ARCH_HAS_GIGANTIC_PAGE */
@@ -1167,6 +1180,13 @@ static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
 {
 	return NULL;
 }
+
+struct page *alloc_gigantic_page_order(unsigned int order, gfp_t gfp_mask,
+				       int nid, nodemask_t *nodemask)
+{
+	return NULL;
+}
+
 static inline void free_gigantic_page(struct page *page, unsigned int order) { }
 static inline void destroy_compound_gigantic_page(struct page *page,
 						unsigned int order) { }
-- 
2.20.1