lkml.org 
[lkml]   [2014]   [Sep]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2] mm: softdirty: addresses before VMAs in PTE holes aren't softdirty
Date
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@google.com>

---

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


\
 
 \ /
  Last update: 2014-09-15 22:01    [W:0.052 / U:0.196 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site