linux-kernel - [PATCH 2/4] arm64: hugetlbpages: Correctly handle swap entries in huge_pte

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Date:   Thu, 30 Mar 2017 17:38:47 +0100
From:   Punit Agrawal <punit.agrawal@....com>
To:     catalin.marinas@....com, will.deacon@....com,
        akpm@...ux-foundation.org
Cc:     Punit Agrawal <punit.agrawal@....com>, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        tbaicar@...eaurora.org, kirill.shutemov@...ux.intel.com,
        mike.kravetz@...cle.com, David Woods <dwoods@...lanox.com>
Subject: [PATCH 2/4] arm64: hugetlbpages: Correctly handle swap entries in huge_pte_offset()

huge_pte_offset() does not correctly handle poisoned or migration page
table entries. Not knowing the size of the hugepage entry being
requested only compounded the problem.

The recently added hstate parameter can be used to determine the size of
hugepage being accessed. Use the size to find the correct page table
entry to return when coming across a swap page table entry.

Signed-off-by: Punit Agrawal <punit.agrawal@....com>
Cc: David Woods <dwoods@...lanox.com>
---
 arch/arm64/mm/hugetlbpage.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 9ca742c4c1ab..44014403081f 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -192,38 +192,39 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
 pte_t *huge_pte_offset(struct mm_struct *mm,
 		       unsigned long addr, struct hstate *h)
 {
+	unsigned long sz = huge_page_size(h);
 	pgd_t *pgd;
 	pud_t *pud;
-	pmd_t *pmd = NULL;
-	pte_t *pte = NULL;
+	pmd_t *pmd;
+	pte_t *pte;
 
 	pgd = pgd_offset(mm, addr);
 	pr_debug("%s: addr:0x%lx pgd:%p\n", __func__, addr, pgd);
 	if (!pgd_present(*pgd))
 		return NULL;
+
 	pud = pud_offset(pgd, addr);
-	if (!pud_present(*pud))
+	if (pud_none(*pud) && sz != PUD_SIZE)
 		return NULL;
-
-	if (pud_huge(*pud))
+	else if (!pud_table(*pud))
 		return (pte_t *)pud;
+
+	if (sz == CONT_PMD_SIZE)
+		addr &= CONT_PMD_MASK;
+
 	pmd = pmd_offset(pud, addr);
-	if (!pmd_present(*pmd))
+	if (pmd_none(*pmd) &&
+	    !(sz == PMD_SIZE || sz == CONT_PMD_SIZE))
 		return NULL;
-
-	if (pte_cont(pmd_pte(*pmd))) {
-		pmd = pmd_offset(
-			pud, (addr & CONT_PMD_MASK));
-		return (pte_t *)pmd;
-	}
-	if (pmd_huge(*pmd))
+	else if (!pmd_table(*pmd))
 		return (pte_t *)pmd;
-	pte = pte_offset_kernel(pmd, addr);
-	if (pte_present(*pte) && pte_cont(*pte)) {
+
+	if (sz == CONT_PTE_SIZE) {
 		pte = pte_offset_kernel(
 			pmd, (addr & CONT_PTE_MASK));
 		return pte;
 	}
+
 	return NULL;
 }
 
-- 
2.11.0