From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 4C6092802A5 for ; Fri, 10 Nov 2017 19:52:49 -0500 (EST) Received: by mail-pg0-f71.google.com with SMTP id 190so5848198pgh.16 for ; Fri, 10 Nov 2017 16:52:49 -0800 (PST) Received: from mga11.intel.com ([192.55.52.93]) by mx.google.com with ESMTPS id n61si9934472plb.463.2017.11.10.16.52.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 10 Nov 2017 16:52:47 -0800 (PST) Subject: [PATCH 1/4] mm: fix device-dax pud write-faults triggered by get_user_pages() From: Dan Williams Date: Fri, 10 Nov 2017 16:44:31 -0800 Message-ID: <151036107109.32713.17139406817769204290.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <151036106541.32713.16875776773735515483.stgit@dwillia2-desk3.amr.corp.intel.com> References: <151036106541.32713.16875776773735515483.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: linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux-mm@kvack.org, Dave Hansen , "Kirill A. Shutemov" Currently only get_user_pages_fast() can safely handle the writable gup case due to its use of pud_access_permitted() to check whether the pud entry is writable. In the gup slow path pud_write() is used instead of pud_access_permitted() and to date it has been unimplemented, just calls BUG_ON(). kernel BUG at ./include/linux/hugetlb.h:244! [..] RIP: 0010:follow_devmap_pud+0x482/0x490 [..] Call Trace: follow_page_mask+0x28c/0x6e0 __get_user_pages+0xe4/0x6c0 get_user_pages_unlocked+0x130/0x1b0 get_user_pages_fast+0x89/0xb0 iov_iter_get_pages_alloc+0x114/0x4a0 nfs_direct_read_schedule_iovec+0xd2/0x350 ? nfs_start_io_direct+0x63/0x70 nfs_file_direct_read+0x1e0/0x250 nfs_file_read+0x90/0xc0 For now this just implements a simple check for the _PAGE_RW bit similar to pmd_write. However, this implies that the gup-slow-path check is missing the extra checks that the gup-fast-path performs with pud_access_permitted. Later patches will align all checks to use the 'access_permitted' helper if the architecture provides it. Note that the generic 'access_permitted' helper fallback is the simple _PAGE_RW check on architectures that do not define the 'access_permitted' helper(s). Cc: Cc: Dave Hansen Cc: Kirill A. Shutemov Fixes: a00cc7d9dd93 ("mm, x86: add support for PUD-sized transparent hugepages") Signed-off-by: Dan Williams --- arch/x86/include/asm/pgtable.h | 6 ++++++ include/asm-generic/pgtable.h | 9 +++++++++ include/linux/hugetlb.h | 8 -------- 3 files changed, 15 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index f735c3016325..5c396724fd0d 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1093,6 +1093,12 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm, clear_bit(_PAGE_BIT_RW, (unsigned long *)pmdp); } +#define __HAVE_ARCH_PUD_WRITE +static inline int pud_write(pud_t pud) +{ + return pud_flags(pud) & _PAGE_RW; +} + /* * clone_pgd_range(pgd_t *dst, pgd_t *src, int count); * diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index 757dc6ffc7ba..bd738624bd16 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -812,6 +812,15 @@ static inline int pmd_write(pmd_t pmd) return 0; } #endif /* __HAVE_ARCH_PMD_WRITE */ + +#ifndef __HAVE_ARCH_PUD_WRITE +static inline int pud_write(pud_t pud) +{ + BUG(); + return 0; +} +#endif /* __HAVE_ARCH_PUD_WRITE */ + #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #if !defined(CONFIG_TRANSPARENT_HUGEPAGE) || \ diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index fbf5b31d47ee..82a25880714a 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -239,14 +239,6 @@ static inline int pgd_write(pgd_t pgd) } #endif -#ifndef pud_write -static inline int pud_write(pud_t pud) -{ - BUG(); - return 0; -} -#endif - #define HUGETLB_ANON_FILE "anon_hugepage" enum { -- 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