mm: make vm_area_dup() actually copy the old vma data

.. and re-initialize th eanon_vma_chain head.

This removes some boiler-plate from the users, and also makes it clear
why it didn't need use the 'zalloc()' version.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 0e23deb5acfc..67253e41bfb0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -315,7 +315,13 @@ struct vm_area_struct *vm_area_alloc(void)
 
 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 {
-        return kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
+        struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
+
+        if (new) {
+                *new = *orig;
+                INIT_LIST_HEAD(&new->anon_vma_chain);
+        }
+        return new;
 }
 
 void vm_area_free(struct vm_area_struct *vma)
@@ -473,8 +479,6 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
                 tmp = vm_area_dup(mpnt);
                 if (!tmp)
                         goto fail_nomem;
-                *tmp = *mpnt;
-                INIT_LIST_HEAD(&tmp->anon_vma_chain);
                 retval = vma_dup_policy(mpnt, tmp);
                 if (retval)
                         goto fail_nomem_policy;