[PATCH 4/4] oom-reaper: use madvise_dontneed() logic to decide if unmap the VMA

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

Logic on whether we can reap pages from the VMA should match what we
have in madvise_dontneed(). In particular, we should skip, VM_PFNMAP
VMAs, but we don't now.

Let's just extract condition on which we can shoot down pagesi from a
VMA with MADV_DONTNEED into separate function and use it in both places.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 mm/internal.h | 5 +++++
 mm/madvise.c  | 2 +-
 mm/oom_kill.c | 9 +--------
 3 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 44d68895a9b9..7430628bff34 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -41,6 +41,11 @@ int do_swap_page(struct vm_fault *vmf);
 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
 		unsigned long floor, unsigned long ceiling);
 
+static inline bool can_madv_dontneed_vma(struct vm_area_struct *vma)
+{
+	return !(vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP));
+}
+
 void unmap_page_range(struct mmu_gather *tlb,
 			     struct vm_area_struct *vma,
 			     unsigned long addr, unsigned long end,
diff --git a/mm/madvise.c b/mm/madvise.c
index aa4c502caecb..20200dfbd1bb 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -473,7 +473,7 @@ static long madvise_dontneed(struct vm_area_struct *vma,
 			     unsigned long start, unsigned long end)
 {
 	*prev = vma;
-	if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
+	if (!can_madv_dontneed_vma(vma))
 		return -EINVAL;
 
 	zap_page_range(vma, start, end - start);
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 96a53ab0c9eb..b6d8ac4948db 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -508,14 +508,7 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
 
 	tlb_gather_mmu(&tlb, mm, 0, -1);
 	for (vma = mm->mmap ; vma; vma = vma->vm_next) {
-		if (is_vm_hugetlb_page(vma))
-			continue;
-
-		/*
-		 * mlocked VMAs require explicit munlocking before unmap.
-		 * Let's keep it simple here and skip such VMAs.
-		 */
-		if (vma->vm_flags & VM_LOCKED)
+		if (!can_madv_dontneed_vma(vma))
 			continue;
 
 		/*
-- 
2.10.2