Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1768824Ab2KOT0B (ORCPT ); Thu, 15 Nov 2012 14:26:01 -0500 Received: from mga14.intel.com ([143.182.124.37]:5568 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423678Ab2KOTZ5 (ORCPT ); Thu, 15 Nov 2012 14:25:57 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.83,259,1352102400"; d="scan'208";a="168868135" From: "Kirill A. Shutemov" To: Andrew Morton , Andrea Arcangeli , linux-mm@kvack.org Cc: Andi Kleen , "H. Peter Anvin" , linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , David Rientjes , "Kirill A. Shutemov" Subject: [PATCH v6 03/12] thp: copy_huge_pmd(): copy huge zero page Date: Thu, 15 Nov 2012 21:26:53 +0200 Message-Id: <1353007622-18393-4-git-send-email-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1353007622-18393-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1353007622-18393-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1934 Lines: 60 From: "Kirill A. Shutemov" It's easy to copy huge zero page. Just set destination pmd to huge zero page. It's safe to copy huge zero page since we have none yet :-p Signed-off-by: Kirill A. Shutemov --- mm/huge_memory.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index fc2cada..183127c 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -701,6 +701,18 @@ static inline struct page *alloc_hugepage(int defrag) } #endif +static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, + struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd) +{ + pmd_t entry; + entry = pfn_pmd(huge_zero_pfn, vma->vm_page_prot); + entry = pmd_wrprotect(entry); + entry = pmd_mkhuge(entry); + set_pmd_at(mm, haddr, pmd, entry); + pgtable_trans_huge_deposit(mm, pgtable); + mm->nr_ptes++; +} + int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, unsigned int flags) @@ -778,6 +790,16 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pte_free(dst_mm, pgtable); goto out_unlock; } + /* + * mm->pagetable lock is enough to be sure that huge zero pmd is not + * under splitting since we don't split the page itself, only pmd to + * a page table. + */ + if (is_huge_zero_pmd(pmd)) { + set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd); + ret = 0; + goto out_unlock; + } if (unlikely(pmd_trans_splitting(pmd))) { /* split huge page running from under us */ spin_unlock(&src_mm->page_table_lock); -- 1.7.11.7 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/