1 files changed, 6 insertions, 1 deletions

diff --git a/mm/mlock.c b/mm/mlock.c
index b70919ce4f72..4f318642fbbe 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -171,7 +171,12 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma,
         VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
 
         gup_flags = FOLL_TOUCH | FOLL_GET;
-        if (vma->vm_flags & VM_WRITE)
+        /*
+         * We want to touch writable mappings with a write fault in order
+         * to break COW, except for shared mappings because these don't COW
+         * and we would not want to dirty them for nothing.
+         */
+        if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
                 gup_flags |= FOLL_WRITE;
 
         /* We don't try to access the guard page of a stack vma */