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>

3 files changed, 7 insertions, 11 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;
diff --git a/mm/mmap.c b/mm/mmap.c
index 4286ad2dd1f5..b0ed8ce1b67e 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2624,11 +2624,6 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
         if (!new)
                 return -ENOMEM;
 
-        /* most fields are the same, copy all, and then fixup */
-        *new = *vma;
-
-        INIT_LIST_HEAD(&new->anon_vma_chain);
-
         if (new_below)
                 new->vm_end = addr;
         else {
@@ -3205,13 +3200,11 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
                 new_vma = vm_area_dup(vma);
                 if (!new_vma)
                         goto out;
-                *new_vma = *vma;
                 new_vma->vm_start = addr;
                 new_vma->vm_end = addr + len;
                 new_vma->vm_pgoff = pgoff;
                 if (vma_dup_policy(vma, new_vma))
                         goto out_free_vma;
-                INIT_LIST_HEAD(&new_vma->anon_vma_chain);
                 if (anon_vma_clone(new_vma, vma))
                         goto out_free_mempol;
                 if (new_vma->vm_file)
diff --git a/mm/nommu.c b/mm/nommu.c
index 006e3fe65017..c2560e9cc803 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1476,7 +1476,6 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
         }
 
         /* most fields are the same, copy all, and then fixup */
-        *new = *vma;
         *region = *vma->vm_region;
         new->vm_region = region;