UBIFS: use kmemdup rather than duplicating its implementation

The patch was generated using fixed coccinelle semantic patch
scripts/coccinelle/api/memdup.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2014320

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
diff --git a/fs/ubifs/tnc.c b/fs/ubifs/tnc.c
index 957f575..fa9a20c 100644
--- a/fs/ubifs/tnc.c
+++ b/fs/ubifs/tnc.c
@@ -198,11 +198,10 @@
 {
 	struct ubifs_znode *zn;
 
-	zn = kmalloc(c->max_znode_sz, GFP_NOFS);
+	zn = kmemdup(znode, c->max_znode_sz, GFP_NOFS);
 	if (unlikely(!zn))
 		return ERR_PTR(-ENOMEM);
 
-	memcpy(zn, znode, c->max_znode_sz);
 	zn->cnext = NULL;
 	__set_bit(DIRTY_ZNODE, &zn->flags);
 	__clear_bit(COW_ZNODE, &zn->flags);