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 68b5a652485682f67eacdee3deae640fb7845b63. The aforementioned patch 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 <[email protected]> --- v1 -> v2: Rewrote to make logic easier to follow. --- 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 dfc791c..c341568 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; } -- 2.1.0.rc2.206.gedb03e5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
