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 <pfeiner@google.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Jamie Liu <jamieliu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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 @@
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;
}