[patch 3/4] vfs: fix ERR_PTR abuse in generic_readlink

generic_readlink calls ERR_PTR for negative and positive values
(vfs_readlink returns length of "link"), but it should not
(not an errno) and does not need to.
Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Acked-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -2856,16 +2856,17 @@ int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 {
 	struct nameidata nd;
 	void *cookie;
+	int res;
 
 	nd.depth = 0;
 	cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
-	if (!IS_ERR(cookie)) {
-		int res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
-		if (dentry->d_inode->i_op->put_link)
-			dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
-		cookie = ERR_PTR(res);
-	}
-	return PTR_ERR(cookie);
+	if (IS_ERR(cookie))
+		return PTR_ERR(cookie);
+
+	res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
+	if (dentry->d_inode->i_op->put_link)
+		dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
+	return res;
 }
 
 int vfs_follow_link(struct nameidata *nd, const char *link)