linux-kernel - [RFC 1/9] mm/hugetlb: Make GENERAL_HUGETLB functions PGD implementation aware

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Date:	Wed,  9 Mar 2016 17:40:42 +0530
From:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Cc:	hughd@...gle.com, kirill@...temov.name, n-horiguchi@...jp.nec.com,
	akpm@...ux-foundation.org, mgorman@...hsingularity.net,
	aneesh.kumar@...ux.vnet.ibm.com, mpe@...erman.id.au
Subject: [RFC 1/9] mm/hugetlb: Make GENERAL_HUGETLB functions PGD implementation aware

Currently both the ARCH_WANT_GENERAL_HUGETLB functions 'huge_pte_alloc'
and 'huge_pte_offset' dont take into account huge page implementation
at the PGD level. With addition of PGD awareness into these functions,
more architectures like POWER which also implements huge pages at PGD
level (along with PMD level), can use ARCH_WANT_GENERAL_HUGETLB option.

Signed-off-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
---
 mm/hugetlb.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 01f2b48..a478b7b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4251,6 +4251,11 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
 	pte_t *pte = NULL;
 
 	pgd = pgd_offset(mm, addr);
+	if (sz == PGDIR_SIZE) {
+		pte = (pte_t *)pgd;
+		goto huge_pgd;
+	}
+
 	pud = pud_alloc(mm, pgd, addr);
 	if (pud) {
 		if (sz == PUD_SIZE) {
@@ -4263,6 +4268,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
 				pte = (pte_t *)pmd_alloc(mm, pud, addr);
 		}
 	}
+
+huge_pgd:
 	BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));
 
 	return pte;
@@ -4276,6 +4283,8 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 
 	pgd = pgd_offset(mm, addr);
 	if (pgd_present(*pgd)) {
+		if (pgd_huge(*pgd))
+			return (pte_t *)pgd;
 		pud = pud_offset(pgd, addr);
 		if (pud_present(*pud)) {
 			if (pud_huge(*pud))
-- 
2.1.0