linux-kernel - [PATCH v2 2/2] sparc64: Fix pagetable freeing for hugepage regions

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Date:	Thu, 23 Jun 2016 15:05:36 -0700
From:	Nitin Gupta <nitin.m.gupta@...cle.com>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	Nitin Gupta <nitin.m.gupta@...cle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dominik Dingel <dingel@...ux.vnet.ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] sparc64: Fix pagetable freeing for hugepage regions

8M pages now allocate page tables till PMD level only.
So, when freeing page table for 8M hugepage backed region,
make sure we don't try to access non-existent PTE level.

Signed-off-by: Nitin Gupta <nitin.m.gupta@...cle.com>
---
 arch/sparc/include/asm/hugetlb.h |   12 ++---
 arch/sparc/mm/hugetlbpage.c      |   98 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 102 insertions(+), 8 deletions(-)

diff --git a/arch/sparc/include/asm/hugetlb.h b/arch/sparc/include/asm/hugetlb.h
index 139e711..dcbf985 100644
--- a/arch/sparc/include/asm/hugetlb.h
+++ b/arch/sparc/include/asm/hugetlb.h
@@ -31,14 +31,6 @@ static inline int prepare_hugepage_range(struct file *file,
 	return 0;
 }
 
-static inline void hugetlb_free_pgd_range(struct mmu_gather *tlb,
-					  unsigned long addr, unsigned long end,
-					  unsigned long floor,
-					  unsigned long ceiling)
-{
-	free_pgd_range(tlb, addr, end, floor, ceiling);
-}
-
 static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,
 					 unsigned long addr, pte_t *ptep)
 {
@@ -82,4 +74,8 @@ static inline void arch_clear_hugepage_flags(struct page *page)
 {
 }
 
+void hugetlb_free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
+			    unsigned long end, unsigned long floor,
+			    unsigned long ceiling);
+
 #endif /* _ASM_SPARC64_HUGETLB_H */
diff --git a/arch/sparc/mm/hugetlbpage.c b/arch/sparc/mm/hugetlbpage.c
index cafb5ca..494c390 100644
--- a/arch/sparc/mm/hugetlbpage.c
+++ b/arch/sparc/mm/hugetlbpage.c
@@ -12,6 +12,7 @@
 
 #include <asm/mman.h>
 #include <asm/pgalloc.h>
+#include <asm/pgtable.h>
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 #include <asm/cacheflush.h>
@@ -202,3 +203,100 @@ int pud_huge(pud_t pud)
 {
 	return 0;
 }
+
+static void hugetlb_free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
+			   unsigned long addr)
+{
+	pgtable_t token = pmd_pgtable(*pmd);
+
+	pmd_clear(pmd);
+	pte_free_tlb(tlb, token, addr);
+	atomic_long_dec(&tlb->mm->nr_ptes);
+}
+
+static void hugetlb_free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
+				   unsigned long addr, unsigned long end,
+				   unsigned long floor, unsigned long ceiling)
+{
+	pmd_t *pmd;
+	unsigned long next;
+	unsigned long start;
+
+	start = addr;
+	pmd = pmd_offset(pud, addr);
+	do {
+		next = pmd_addr_end(addr, end);
+		if (pmd_none(*pmd))
+			continue;
+		if (is_hugetlb_pmd(*pmd))
+			pmd_clear(pmd);
+		else
+			hugetlb_free_pte_range(tlb, pmd, addr);
+	} while (pmd++, addr = next, addr != end);
+
+	start &= PUD_MASK;
+	if (start < floor)
+		return;
+	if (ceiling) {
+		ceiling &= PUD_MASK;
+		if (!ceiling)
+			return;
+	}
+	if (end - 1 > ceiling - 1)
+		return;
+
+	pmd = pmd_offset(pud, start);
+	pud_clear(pud);
+	pmd_free_tlb(tlb, pmd, start);
+	mm_dec_nr_pmds(tlb->mm);
+}
+
+static void hugetlb_free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
+				   unsigned long addr, unsigned long end,
+				   unsigned long floor, unsigned long ceiling)
+{
+	pud_t *pud;
+	unsigned long next;
+	unsigned long start;
+
+	start = addr;
+	pud = pud_offset(pgd, addr);
+	do {
+		next = pud_addr_end(addr, end);
+		if (pud_none_or_clear_bad(pud))
+			continue;
+		hugetlb_free_pmd_range(tlb, pud, addr, next, floor,
+				       ceiling);
+	} while (pud++, addr = next, addr != end);
+
+	start &= PGDIR_MASK;
+	if (start < floor)
+		return;
+	if (ceiling) {
+		ceiling &= PGDIR_MASK;
+		if (!ceiling)
+			return;
+	}
+	if (end - 1 > ceiling - 1)
+		return;
+
+	pud = pud_offset(pgd, start);
+	pgd_clear(pgd);
+	pud_free_tlb(tlb, pud, start);
+}
+
+void hugetlb_free_pgd_range(struct mmu_gather *tlb,
+			    unsigned long addr, unsigned long end,
+			    unsigned long floor, unsigned long ceiling)
+{
+	pgd_t *pgd;
+	unsigned long next;
+
+	pgd = pgd_offset(tlb->mm, addr);
+	do {
+		next = pgd_addr_end(addr, end);
+		if (pgd_none_or_clear_bad(pgd))
+			continue;
+		hugetlb_free_pud_range(tlb, pgd, addr, next, floor, ceiling);
+	} while (pgd++, addr = next, addr != end);
+}
-- 
1.7.1