The patch titled
Subject: mm: mlock: avoid increase mm->locked_vm on mlock() when already mlock2(,MLOCK_ONFAULT)
has been added to the -mm tree. Its filename is
mm-mlock-avoid-increase-mm-locked_vm-on-mlock-when-already-mlock2mlock_onfault.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-mlock-avoid-increase-mm-locked_vm-on-mlock-when-already-mlock2mlock_onfault.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-mlock-avoid-increase-mm-locked_vm-on-mlock-when-already-mlock2mlock_onfault.patch
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From: Simon Guo <wei.guo.simon@xxxxxxxxx>
Subject: mm: mlock: avoid increase mm->locked_vm on mlock() when already mlock2(,MLOCK_ONFAULT)
When one vma was with flag VM_LOCKED|VM_LOCKONFAULT (by invoking
mlock2(,MLOCK_ONFAULT)), it can again be populated with mlock() with
VM_LOCKED flag only.
There is a hole in mlock_fixup() which increase mm->locked_vm twice even
the two operations are on the same vma and both with VM_LOCKED flags.
The issue can be reproduced by following code:
mlock2(p, 1024 * 64, MLOCK_ONFAULT); //VM_LOCKED|VM_LOCKONFAULT
mlock(p, 1024 * 64); //VM_LOCKED
Then check the increase VmLck field in /proc/pid/status(to 128k).
When vma is set with different vm_flags, and the new vm_flags is with
VM_LOCKED, it is not necessarily be a "new locked" vma. This patch
corrects this bug by prevent mm->locked_vm from increment when old
vm_flags is already VM_LOCKED.
Link: http://lkml.kernel.org/r/1472554781-9835-3-git-send-email-wei.guo.simon@xxxxxxxxx
Signed-off-by: Simon Guo <wei.guo.simon@xxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Alexey Klimov <klimov.linux@xxxxxxxxx>
Cc: Eric B Munson <emunson@xxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Simon Guo <wei.guo.simon@xxxxxxxxx>
Cc: Thierry Reding <treding@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mlock.c | 3 +++
1 file changed, 3 insertions(+)
diff -puN mm/mlock.c~mm-mlock-avoid-increase-mm-locked_vm-on-mlock-when-already-mlock2mlock_onfault mm/mlock.c
--- a/mm/mlock.c~mm-mlock-avoid-increase-mm-locked_vm-on-mlock-when-already-mlock2mlock_onfault
+++ a/mm/mlock.c
@@ -516,6 +516,7 @@ static int mlock_fixup(struct vm_area_st
int nr_pages;
int ret = 0;
int lock = !!(newflags & VM_LOCKED);
+ vm_flags_t old_flags = vma->vm_flags;
if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
@@ -550,6 +551,8 @@ success:
nr_pages = (end - start) >> PAGE_SHIFT;
if (!lock)
nr_pages = -nr_pages;
+ else if (old_flags & VM_LOCKED)
+ nr_pages = 0;
mm->locked_vm += nr_pages;
/*
_
Patches currently in -mm which might be from wei.guo.simon@xxxxxxxxx are
mm-mlock-check-against-vma-for-actual-mlock-size.patch
mm-mlock-avoid-increase-mm-locked_vm-on-mlock-when-already-mlock2mlock_onfault.patch
selftest-split-mlock2_-funcs-into-separate-mlock2h.patch
selftests-vm-add-test-for-mlock-when-areas-are-intersected.patch
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