rmap: anon_vma_prepare: Reduce code duplication by calling anon_vma_chain_link

Reduce code duplication by calling anon_vma_chain_link() from
anon_vma_prepare().

Also move anon_vmal_chain_link() to a more suitable location in the file.
Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hughd@google.com>
Reviewed-by: KAMEZWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/rmap.c

@@ -120,6 +120,21 @@ static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
 	kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
 }
 
+static void anon_vma_chain_link(struct vm_area_struct *vma,
+				struct anon_vma_chain *avc,
+				struct anon_vma *anon_vma)
+{
+	avc->vma = vma;
+	avc->anon_vma = anon_vma;
+	list_add(&avc->same_vma, &vma->anon_vma_chain);
+
+	/*
+	 * It's critical to add new vmas to the tail of the anon_vma,
+	 * see comment in huge_memory.c:__split_huge_page().
+	 */
+	list_add_tail(&avc->same_anon_vma, &anon_vma->head);
+}
+
 /**
  * anon_vma_prepare - attach an anon_vma to a memory region
  * @vma: the memory region in question
@@ -175,10 +190,7 @@ int anon_vma_prepare(struct vm_area_struct *vma)
 		spin_lock(&mm->page_table_lock);
 		if (likely(!vma->anon_vma)) {
 			vma->anon_vma = anon_vma;
-			avc->anon_vma = anon_vma;
-			avc->vma = vma;
-			list_add(&avc->same_vma, &vma->anon_vma_chain);
-			list_add_tail(&avc->same_anon_vma, &anon_vma->head);
+			anon_vma_chain_link(vma, avc, anon_vma);
 			allocated = NULL;
 			avc = NULL;
 		}
@@ -224,21 +236,6 @@ static inline void unlock_anon_vma_root(struct anon_vma *root)
 		mutex_unlock(&root->mutex);
 }
 
-static void anon_vma_chain_link(struct vm_area_struct *vma,
-				struct anon_vma_chain *avc,
-				struct anon_vma *anon_vma)
-{
-	avc->vma = vma;
-	avc->anon_vma = anon_vma;
-	list_add(&avc->same_vma, &vma->anon_vma_chain);
-
-	/*
-	 * It's critical to add new vmas to the tail of the anon_vma,
-	 * see comment in huge_memory.c:__split_huge_page().
-	 */
-	list_add_tail(&avc->same_anon_vma, &anon_vma->head);
-}
-
 /*
  * Attach the anon_vmas from src to dst.
  * Returns 0 on success, -ENOMEM on failure.