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mm: softdirty: addresses before VMAs in PTE holes aren't softdirty

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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 68b5a65248 ("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 <[email protected]>
Cc: Cyrill Gorcunov <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Jamie Liu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Peter Feiner 2014-09-25 16:05:18 -07:00 • committed by Linus Torvalds
commit 87e6d49a00
1 changed files with 18 additions and 9 deletions
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27
fs/proc/task_mmu.c
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@ -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;
}