From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933391AbbCFKBp (ORCPT ); Fri, 6 Mar 2015 05:01:45 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:44972 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933345AbbCFKB2 (ORCPT ); Fri, 6 Mar 2015 05:01:28 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Peter Feiner , "Kirill A. Shutemov" , Cyrill Gorcunov , Pavel Emelyanov , Jamie Liu , Hugh Dickins , Naoya Horiguchi , Andrew Morton , Linus Torvalds , Luis Henriques Subject: [PATCH 3.16.y-ckt 178/183] mm: softdirty: unmapped addresses between VMAs are clean Date: Fri, 6 Mar 2015 09:57:49 +0000 Message-Id: <1425635874-19087-179-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1425635874-19087-1-git-send-email-luis.henriques@canonical.com> References: <1425635874-19087-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.7-ckt8 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Feiner commit 81d0fa623c5b8dbd5279d9713094b0f9b0a00fb4 upstream. If a /proc/pid/pagemap read spans a [VMA, an unmapped region, then a VM_SOFTDIRTY VMA], the virtual pages in the unmapped region are reported as softdirty. Here's a program to demonstrate the bug: int main() { const uint64_t PAGEMAP_SOFTDIRTY = 1ul << 55; uint64_t pme[3]; int fd = open("/proc/self/pagemap", O_RDONLY);; char *m = mmap(NULL, 3 * getpagesize(), PROT_READ, MAP_ANONYMOUS | MAP_SHARED, -1, 0); munmap(m + getpagesize(), getpagesize()); pread(fd, pme, 24, (unsigned long) m / getpagesize() * 8); assert(pme[0] & PAGEMAP_SOFTDIRTY); /* passes */ assert(!(pme[1] & PAGEMAP_SOFTDIRTY)); /* fails */ assert(pme[2] & PAGEMAP_SOFTDIRTY); /* passes */ return 0; } (Note that all pages in new VMAs are softdirty until cleared). Tested: Used the program given above. I'm going to include this code in a selftest in the future. [n-horiguchi@ah.jp.nec.com: prevent pagemap_pte_range() from overrunning] Signed-off-by: Peter Feiner Cc: "Kirill A. Shutemov" Cc: Cyrill Gorcunov Cc: Pavel Emelyanov Cc: Jamie Liu Cc: Hugh Dickins Cc: Naoya Horiguchi Signed-off-by: Naoya Horiguchi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [ luis: 3.16-stable prereq for: 05fbf357d941 "proc/pagemap: walk page tables under pte lock" ] Signed-off-by: Luis Henriques --- fs/proc/task_mmu.c | 61 +++++++++++++++++++++++++++++++++++------------------- 1 file changed, 40 insertions(+), 21 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index cfa63ee92c96..143674aef97c 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1005,7 +1005,6 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, spinlock_t *ptl; pte_t *pte; int err = 0; - pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2)); /* find the first VMA at or above 'addr' */ vma = find_vma(walk->mm, addr); @@ -1019,6 +1018,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, for (; addr != end; addr += PAGE_SIZE) { unsigned long offset; + pagemap_entry_t pme; offset = (addr & ~PAGEMAP_WALK_MASK) >> PAGE_SHIFT; @@ -1033,32 +1033,51 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, if (pmd_trans_unstable(pmd)) return 0; - for (; addr != end; addr += PAGE_SIZE) { - int flags2; - - /* check to see if we've left 'vma' behind - * and need a new, higher one */ - if (vma && (addr >= vma->vm_end)) { - vma = find_vma(walk->mm, addr); - if (vma && (vma->vm_flags & VM_SOFTDIRTY)) - flags2 = __PM_SOFT_DIRTY; - else - flags2 = 0; - pme = make_pme(PM_NOT_PRESENT(pm->v2) | PM_STATUS2(pm->v2, flags2)); + + while (1) { + /* End of address space hole, which we mark as non-present. */ + unsigned long hole_end; + + if (vma) + hole_end = min(end, vma->vm_start); + else + hole_end = end; + + for (; addr < hole_end; addr += PAGE_SIZE) { + pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2)); + + err = add_to_pagemap(addr, &pme, pm); + if (err) + return err; } - /* check that 'vma' actually covers this address, - * and that it isn't a huge page vma */ - if (vma && (vma->vm_start <= addr) && - !is_vm_hugetlb_page(vma)) { + if (!vma || vma->vm_start >= end) + break; + /* + * We can't possibly be in a hugetlb VMA. In general, + * for a mm_walk with a pmd_entry and a hugetlb_entry, + * the pmd_entry can only be called on addresses in a + * hugetlb if the walk starts in a non-hugetlb VMA and + * spans a hugepage VMA. Since pagemap_read walks are + * PMD-sized and PMD-aligned, this will never be true. + */ + BUG_ON(is_vm_hugetlb_page(vma)); + + /* Addresses in the VMA. */ + for (; addr < min(end, vma->vm_end); addr += PAGE_SIZE) { + pagemap_entry_t pme; pte = pte_offset_map(pmd, addr); pte_to_pagemap_entry(&pme, pm, vma, addr, *pte); - /* unmap before userspace copy */ pte_unmap(pte); + err = add_to_pagemap(addr, &pme, pm); + if (err) + return err; } - err = add_to_pagemap(addr, &pme, pm); - if (err) - return err; + + if (addr == end) + break; + + vma = find_vma(walk->mm, addr); } cond_resched();