vfs: do_last(): common slow lookup

Make the slow lookup part of O_CREAT and non-O_CREAT opens common.

This allows atomic_open to be hooked into the slow lookup part.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -2250,30 +2250,13 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
 			symlink_ok = 1;
 		/* we _can_ be in RCU mode here */
 		error = lookup_fast(nd, &nd->last, path, &inode);
-		if (unlikely(error)) {
-			if (error < 0)
-				goto exit;
-
-			BUG_ON(nd->inode != dir->d_inode);
-
-			mutex_lock(&dir->d_inode->i_mutex);
-			dentry = __lookup_hash(&nd->last, dir, nd);
-			mutex_unlock(&dir->d_inode->i_mutex);
-			error = PTR_ERR(dentry);
-			if (IS_ERR(dentry))
-				goto exit;
-			path->mnt = nd->path.mnt;
-			path->dentry = dentry;
-			error = follow_managed(path, nd->flags);
-			if (unlikely(error < 0))
-				goto exit_dput;
+		if (likely(!error))
+			goto finish_lookup;
 
-			if (error)
-				nd->flags |= LOOKUP_JUMPED;
+		if (error < 0)
+			goto exit;
 
-			inode = path->dentry->d_inode;
-		}
-		goto finish_lookup;
+		BUG_ON(nd->inode != dir->d_inode);
 	} else {
 		/* create side of things */
 		/*