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 <pfeiner@xxxxxxxxxx>
---
fs/proc/task_mmu.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index dfc791c..256dbe9 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -931,16 +931,26 @@ 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;
+ unsigned long vm_start = end;
+ unsigned long vm_end = end;
+ unsigned long vm_flags = 0;
- if (!vma) {
- vm_end = end;
- } else {
+ if (vma) {
+ vm_start = min(end, vma->vm_start);
vm_end = min(end, vma->vm_end);
- if (vma->vm_flags & VM_SOFTDIRTY)
- pme.pme |= PM_STATUS2(pm->v2, __PM_SOFT_DIRTY);
+ vm_flags = vma->vm_flags;
+ }
+
+ /* Addresses before the VMA. */
+ for (; addr < vm_start; addr += PAGE_SIZE) {
+ err = add_to_pagemap(addr, &pme, pm);
+ if (err)
+ goto out;
}
+ /* Addresses in the VMA. */
+ if (vm_flags & VM_SOFTDIRTY)
+ pme.pme |= PM_STATUS2(pm->v2, __PM_SOFT_DIRTY);
for (; addr < vm_end; addr += PAGE_SIZE) {
err = add_to_pagemap(addr, &pme, pm);
if (err)
--
2.1.0.rc2.206.gedb03e5
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