The patch titled
Subject: mm: softdirty: unmapped addresses between VMAs are clean
has been added to the -mm tree. Its filename is
mm-softdirty-unmapped-addresses-between-vmas-are-clean.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-softdirty-unmapped-addresses-between-vmas-are-clean.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-softdirty-unmapped-addresses-between-vmas-are-clean.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Peter Feiner <pfeiner@xxxxxxxxxx>
Subject: mm: softdirty: unmapped addresses between VMAs are clean
If a /proc/pid/pagemap read spans a [VMA, an unmapped region, then a
VM_SOFTDIRTY VMA], the virtual pages in the unmapped region are reported
as softdirty. Here's a program to demonstrate the bug:
int main() {
const uint64_t PAGEMAP_SOFTDIRTY = 1ul << 55;
uint64_t pme[3];
int fd = open("/proc/self/pagemap", O_RDONLY);;
char *m = mmap(NULL, 3 * getpagesize(), PROT_READ,
MAP_ANONYMOUS | MAP_SHARED, -1, 0);
munmap(m + getpagesize(), getpagesize());
pread(fd, pme, 24, (unsigned long) m / getpagesize() * 8);
assert(pme[0] & PAGEMAP_SOFTDIRTY); /* passes */
assert(!(pme[1] & PAGEMAP_SOFTDIRTY)); /* fails */
assert(pme[2] & PAGEMAP_SOFTDIRTY); /* passes */
return 0;
}
(Note that all pages in new VMAs are softdirty until cleared).
Tested:
Used the program given above. I'm going to include this code in
a selftest in the future.
Signed-off-by: Peter Feiner <pfeiner@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Jamie Liu <jamieliu@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 59 ++++++++++++++++++++++++++++---------------
1 file changed, 39 insertions(+), 20 deletions(-)
diff -puN fs/proc/task_mmu.c~mm-softdirty-unmapped-addresses-between-vmas-are-clean fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~mm-softdirty-unmapped-addresses-between-vmas-are-clean
+++ a/fs/proc/task_mmu.c
@@ -1038,7 +1038,6 @@ static int pagemap_pte_range(pmd_t *pmd,
spinlock_t *ptl;
pte_t *pte;
int err = 0;
- pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2));
/* find the first VMA at or above 'addr' */
vma = find_vma(walk->mm, addr);
@@ -1052,6 +1051,7 @@ static int pagemap_pte_range(pmd_t *pmd,
for (; addr != end; addr += PAGE_SIZE) {
unsigned long offset;
+ pagemap_entry_t pme;
offset = (addr & ~PAGEMAP_WALK_MASK) >>
PAGE_SHIFT;
@@ -1066,32 +1066,51 @@ static int pagemap_pte_range(pmd_t *pmd,
if (pmd_trans_unstable(pmd))
return 0;
- for (; addr != end; addr += PAGE_SIZE) {
- int flags2;
- /* check to see if we've left 'vma' behind
- * and need a new, higher one */
- if (vma && (addr >= vma->vm_end)) {
- vma = find_vma(walk->mm, addr);
- if (vma && (vma->vm_flags & VM_SOFTDIRTY))
- flags2 = __PM_SOFT_DIRTY;
- else
- flags2 = 0;
- pme = make_pme(PM_NOT_PRESENT(pm->v2) | PM_STATUS2(pm->v2, flags2));
+ while (1) {
+ unsigned long vm_start = end;
+ unsigned long vm_end = end;
+ unsigned long vm_flags = 0;
+
+ if (vma) {
+ /*
+ * We can't possibly be in a hugetlb VMA. In general,
+ * for a mm_walk with a pmd_entry and a hugetlb_entry,
+ * the pmd_entry can only be called on addresses in a
+ * hugetlb if the walk starts in a non-hugetlb VMA and
+ * spans a hugepage VMA. Since pagemap_read walks are
+ * PMD-sized and PMD-aligned, this will never be true.
+ */
+ BUG_ON(is_vm_hugetlb_page(vma));
+ vm_start = vma->vm_start;
+ vm_end = min(end, vma->vm_end);
+ vm_flags = vma->vm_flags;
}
- /* check that 'vma' actually covers this address,
- * and that it isn't a huge page vma */
- if (vma && (vma->vm_start <= addr) &&
- !is_vm_hugetlb_page(vma)) {
+ /* Addresses before the VMA. */
+ for (; addr < vm_start; addr += PAGE_SIZE) {
+ pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2));
+
+ err = add_to_pagemap(addr, &pme, pm);
+ if (err)
+ return err;
+ }
+
+ /* Addresses in the VMA. */
+ for (; addr < vm_end; addr += PAGE_SIZE) {
+ pagemap_entry_t pme;
pte = pte_offset_map(pmd, addr);
pte_to_pagemap_entry(&pme, pm, vma, addr, *pte);
- /* unmap before userspace copy */
pte_unmap(pte);
+ err = add_to_pagemap(addr, &pme, pm);
+ if (err)
+ return err;
}
- err = add_to_pagemap(addr, &pme, pm);
- if (err)
- return err;
+
+ if (addr == end)
+ break;
+
+ vma = find_vma(walk->mm, addr);
}
cond_resched();
_
Patches currently in -mm which might be from pfeiner@xxxxxxxxxx are
mm-softdirty-addresses-before-vmas-in-pte-holes-arent-softdirty.patch
mm-softdirty-enable-write-notifications-on-vmas-after-vm_softdirty-cleared.patch
mm-softdirty-unmapped-addresses-between-vmas-are-clean.patch
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