xattr handlers: Simplify list operation

Change the list operation to only return whether or not an attribute
should be listed.  Copying the attribute names into the buffer is moved
to the callers.

Since the result only depends on the dentry and not on the attribute
name, we do not pass the attribute name to list operations.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index dbfade2..c57d133 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -6263,19 +6263,9 @@
 	return nfs4_proc_get_acl(d_inode(dentry), buf, buflen);
 }
 
-static size_t nfs4_xattr_list_nfs4_acl(const struct xattr_handler *handler,
-				       struct dentry *dentry, char *list,
-				       size_t list_len, const char *name,
-				       size_t name_len)
+static bool nfs4_xattr_list_nfs4_acl(struct dentry *dentry)
 {
-	size_t len = sizeof(XATTR_NAME_NFSV4_ACL);
-
-	if (!nfs4_server_supports_acls(NFS_SERVER(d_inode(dentry))))
-		return 0;
-
-	if (list && len <= list_len)
-		memcpy(list, XATTR_NAME_NFSV4_ACL, len);
-	return len;
+	return nfs4_server_supports_acls(NFS_SERVER(d_inode(dentry)));
 }
 
 #ifdef CONFIG_NFS_V4_SECURITY_LABEL