From 87e6d49a000fa6148bd539f632706b02c3485c5d Mon Sep 17 00:00:00 2001 From: Peter Feiner Date: Thu, 25 Sep 2014 16:05:18 -0700 Subject: [PATCH] mm: softdirty: addresses before VMAs in PTE holes aren't softdirty In PTE holes that contain VM_SOFTDIRTY VMAs, unmapped addresses before VM_SOFTDIRTY VMAs are reported as softdirty by /proc/pid/pagemap. This bug was introduced in commit 68b5a6524856 ("mm: softdirty: respect VM_SOFTDIRTY in PTE holes"). That commit made /proc/pid/pagemap look at VM_SOFTDIRTY in PTE holes but neglected to observe the start of VMAs returned by find_vma. Tested: Wrote a selftest that creates a PMD-sized VMA then unmaps the first page and asserts that the page is not softdirty. I'm going to send the pagemap selftest in a later commit. Signed-off-by: Peter Feiner Cc: Cyrill Gorcunov Cc: Pavel Emelyanov Cc: Hugh Dickins Cc: Naoya Horiguchi Cc: "Kirill A. Shutemov" Cc: Jamie Liu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index dfc791c42d64..c34156888d70 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -931,23 +931,32 @@ static int pagemap_pte_hole(unsigned long start, unsigned long end, while (addr < end) { struct vm_area_struct *vma = find_vma(walk->mm, addr); pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2)); - unsigned long vm_end; + /* End of address space hole, which we mark as non-present. */ + unsigned long hole_end; - if (!vma) { - vm_end = end; - } else { - vm_end = min(end, vma->vm_end); - if (vma->vm_flags & VM_SOFTDIRTY) - pme.pme |= PM_STATUS2(pm->v2, __PM_SOFT_DIRTY); + if (vma) + hole_end = min(end, vma->vm_start); + else + hole_end = end; + + for (; addr < hole_end; addr += PAGE_SIZE) { + err = add_to_pagemap(addr, &pme, pm); + if (err) + goto out; } - for (; addr < vm_end; addr += PAGE_SIZE) { + if (!vma) + break; + + /* Addresses in the VMA. */ + if (vma->vm_flags & VM_SOFTDIRTY) + pme.pme |= PM_STATUS2(pm->v2, __PM_SOFT_DIRTY); + for (; addr < min(end, vma->vm_end); addr += PAGE_SIZE) { err = add_to_pagemap(addr, &pme, pm); if (err) goto out; } } - out: return err; } -- GitLab