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 BA7076B0033 for ; Wed, 8 Feb 2017 00:34:18 -0500 (EST) Received: by mail-pf0-f200.google.com with SMTP id f144so179814893pfa.3 for ; Tue, 07 Feb 2017 21:34:18 -0800 (PST) Received: from mga11.intel.com (mga11.intel.com. [192.55.52.93]) by mx.google.com with ESMTPS id m29si6171613pgn.56.2017.02.07.21.34.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 07 Feb 2017 21:34:17 -0800 (PST) Subject: [-mm PATCH] mm: fix get_user_pages() vs device-dax pud mappings From: Dan Williams Date: Tue, 07 Feb 2017 21:30:11 -0800 Message-ID: <148653181153.38226.9605457830505509385.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: Dave Jiang , Matthew Wilcox , linux-nvdimm@lists.01.org, Nilesh Choudhury , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ross Zwisler , "Kirill A. Shutemov" A new unit test for the device-dax 1GB enabling currently fails with this warning before hanging the test thread: WARNING: CPU: 0 PID: 21 at lib/percpu-refcount.c:155 percpu_ref_switch_to_atomic_rcu+0x1e3/0x1f0 percpu ref (dax_pmem_percpu_release [dax_pmem]) <= 0 (0) after switching to atomic [..] CPU: 0 PID: 21 Comm: rcuos/1 Tainted: G O 4.10.0-rc7-next-20170207+ #944 [..] Call Trace: dump_stack+0x86/0xc3 __warn+0xcb/0xf0 warn_slowpath_fmt+0x5f/0x80 ? rcu_nocb_kthread+0x27a/0x510 ? dax_pmem_percpu_exit+0x50/0x50 [dax_pmem] percpu_ref_switch_to_atomic_rcu+0x1e3/0x1f0 ? percpu_ref_exit+0x60/0x60 rcu_nocb_kthread+0x339/0x510 ? rcu_nocb_kthread+0x27a/0x510 kthread+0x101/0x140 The get_user_pages() path needs to arrange for references to be taken against the dev_pagemap instance backing the pud mapping. Refactor the existing __gup_device_huge_pmd() to also account for the pud case. Cc: Dave Jiang Cc: Matthew Wilcox Cc: Ross Zwisler Cc: Kirill A. Shutemov Cc: Nilesh Choudhury Signed-off-by: Dan Williams --- arch/x86/mm/gup.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c index 0d4fb3ebbbac..99c7805a9693 100644 --- a/arch/x86/mm/gup.c +++ b/arch/x86/mm/gup.c @@ -154,14 +154,12 @@ static inline void get_head_page_multiple(struct page *page, int nr) SetPageReferenced(page); } -static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr, +static int __gup_device_huge(unsigned long pfn, unsigned long addr, unsigned long end, struct page **pages, int *nr) { int nr_start = *nr; - unsigned long pfn = pmd_pfn(pmd); struct dev_pagemap *pgmap = NULL; - pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT; do { struct page *page = pfn_to_page(pfn); @@ -180,6 +178,24 @@ static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr, return 1; } +static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr, + unsigned long end, struct page **pages, int *nr) +{ + unsigned long fault_pfn; + + fault_pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); + return __gup_device_huge(fault_pfn, addr, end, pages, nr); +} + +static int __gup_device_huge_pud(pud_t pud, unsigned long addr, + unsigned long end, struct page **pages, int *nr) +{ + unsigned long fault_pfn; + + fault_pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); + return __gup_device_huge(fault_pfn, addr, end, pages, nr); +} + static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr, unsigned long end, int write, struct page **pages, int *nr) { @@ -251,9 +267,13 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr, if (!pte_allows_gup(pud_val(pud), write)) return 0; + + VM_BUG_ON(!pfn_valid(pud_pfn(pud))); + if (pud_devmap(pud)) + return __gup_device_huge_pud(pud, addr, end, pages, nr); + /* hugepages are never "special" */ VM_BUG_ON(pud_flags(pud) & _PAGE_SPECIAL); - VM_BUG_ON(!pfn_valid(pud_pfn(pud))); refs = 0; head = pud_page(pud); -- 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