Re: [PATCH 1/2] mm, oom: skip mlocked VMAs in __oom_reap_vmas()

[Michal Hocko <mhocko@suse.cz>]

On Tue 29-12-15 23:46:29, Kirill A. Shutemov wrote:
> As far as I can see we explicitly munlock pages everywhere before unmap
> them. The only case when we don't to that is OOM-reaper.

Very well spotted!

> I don't think we should bother with munlocking in this case, we can just
> skip the locked VMA.

Why cannot we simply munlock them here for the private mappings?

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 4b0a5d8b92e1..25dd7cd6fb5e 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -456,9 +456,12 @@ static bool __oom_reap_vmas(struct mm_struct *mm)
 		 * we do not want to block exit_mmap by keeping mm ref
 		 * count elevated without a good reason.
 		 */
-		if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED))
+		if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
+			if (vma->vm_flags & VM_LOCKED)
+				munlock_vma_pages_all(vma);
 			unmap_page_range(&tlb, vma, vma->vm_start, vma->vm_end,
 					 &details);
+		}
 	}
 	tlb_finish_mmu(&tlb, 0, -1);
 	up_read(&mm->mmap_sem);
-- 
Michal Hocko
SUSE Labs

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