From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 1F8826B02C3 for ; Mon, 24 Jul 2017 13:33:50 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id v68so135072410pfi.13 for ; Mon, 24 Jul 2017 10:33:50 -0700 (PDT) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id t69si7158830pgd.95.2017.07.24.10.33.48 for ; Mon, 24 Jul 2017 10:33:49 -0700 (PDT) From: Punit Agrawal Subject: [RFC PATCH 1/2] mm/hugetlb: Make huge_pte_offset() consistent between PUD and PMD entries Date: Mon, 24 Jul 2017 18:33:17 +0100 Message-Id: <20170724173318.966-2-punit.agrawal@arm.com> In-Reply-To: <20170724173318.966-1-punit.agrawal@arm.com> References: <20170724173318.966-1-punit.agrawal@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Punit Agrawal , Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, steve.capper@arm.com, will.deacon@arm.com, catalin.marinas@arm.com, kirill.shutemov@linux.intel.com, Michal Hocko , Mike Kravetz When walking the page tables to resolve an address that points to !present_p*d() entry, huge_pte_offset() returns inconsistent values depending on the level of page table (PUD or PMD). In the case of a PUD entry, it returns NULL while in the case of a PMD entry, it returns a pointer to the page table entry. Make huge_pte_offset() consistent by always returning NULL on encountering a !present_p*d() entry. Document the behaviour to clarify the expected semantics of this function. Signed-off-by: Punit Agrawal --- mm/hugetlb.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index bc48ee783dd9..686eb6fa9eb1 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4603,6 +4603,13 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, return pte; } +/* + * huge_pte_offset() - Walk the page table to resolve the hugepage + * entry at address @addr + * + * Return: Pointer to page table entry (PUD or PMD) for address @addr + * or NULL if the entry is not present. + */ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr, unsigned long sz) { @@ -4617,13 +4624,20 @@ pte_t *huge_pte_offset(struct mm_struct *mm, p4d = p4d_offset(pgd, addr); if (!p4d_present(*p4d)) return NULL; + pud = pud_offset(p4d, addr); if (!pud_present(*pud)) return NULL; if (pud_huge(*pud)) return (pte_t *)pud; + pmd = pmd_offset(pud, addr); - return (pte_t *) pmd; + if (!pmd_present(*pmd)) + return NULL; + if (pmd_huge(*pmd)) + return (pte_t *) pmd; + + return NULL; } #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */ -- 2.11.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org