From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2B3FC433F5 for ; Wed, 6 Oct 2021 15:22:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6BF6660FC2 for ; Wed, 6 Oct 2021 15:22:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 6BF6660FC2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id B21906B006C; Wed, 6 Oct 2021 11:22:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AD1D06B0071; Wed, 6 Oct 2021 11:22:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9E787900002; Wed, 6 Oct 2021 11:22:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0153.hostedemail.com [216.40.44.153]) by kanga.kvack.org (Postfix) with ESMTP id 91D5A6B006C for ; Wed, 6 Oct 2021 11:22:31 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 4F796183E46EE for ; Wed, 6 Oct 2021 15:22:31 +0000 (UTC) X-FDA: 78666379302.21.34B7C9B Received: from zeniv-ca.linux.org.uk (zeniv-ca.linux.org.uk [142.44.231.140]) by imf20.hostedemail.com (Postfix) with ESMTP id CAAA9D00024D for ; Wed, 6 Oct 2021 15:22:30 +0000 (UTC) Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mY8kX-00AWIy-GM; Wed, 06 Oct 2021 15:22:29 +0000 Date: Wed, 6 Oct 2021 15:22:29 +0000 From: Al Viro To: Matthew Wilcox Cc: linux-mm@kvack.org, David Hildenbrand , Kent Overstreet , Johannes Weiner , linux-fsdevel@vger.kernel.org Subject: Re: [RFC] pgflags_t Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: CAAA9D00024D X-Stat-Signature: u1uwpi1merw3ufr37cztbxmr65j76jso Authentication-Results: imf20.hostedemail.com; dkim=none; dmarc=none; spf=none (imf20.hostedemail.com: domain of viro@ftp.linux.org.uk has no SPF policy when checking 142.44.231.140) smtp.mailfrom=viro@ftp.linux.org.uk X-HE-Tag: 1633533750-876731 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000026, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Oct 06, 2021 at 03:58:14PM +0100, Matthew Wilcox wrote: > David expressed some unease about the lack of typesafety in patches > 1 & 2 of the page->slab conversion [1], and I'll admit to not being > particularly a fan of passing around an unsigned long. That crystallised > in a discussion with Kent [2] about how to lock a page when you don't know > its type (solution: every memory descriptor type starts with a > pgflags_t) Why bother making it a struct? What's wrong with __bitwise and letting sparse catch conversions?