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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DDF7C49EA3 for ; Mon, 28 Jun 2021 15:54:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E0D426023B for ; Mon, 28 Jun 2021 15:54:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235329AbhF1P4v (ORCPT ); Mon, 28 Jun 2021 11:56:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235132AbhF1P4e (ORCPT ); Mon, 28 Jun 2021 11:56:34 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0FD89C058B05; Mon, 28 Jun 2021 08:45:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=7p3ZErU459kzXpwH69SdGsHIsa2wrWdtYOXOZ1fJP8c=; b=JhRzUPgcCrJIWJsK3FwDl0OlPC X+8ZgMfTejZ3tHRU44TZQdOdnLkKkTdmSZvTZ8K0oFpaMQFONI6TjeIjj+ZBbqZfz/ehfbrk9s88m +QFPdPYbMAqlrHAhxkgggEuA9q7JD87ntSum7R8qJ22YbMvQ46Rp3S5wrzRZNvjXLJmFBmrXIqNDD bExBPBzhsDVegpzJnTcncBgRMPniX/b5zSsCRqe4VG4lpBVH6AKs0CKHY/ARoyI3KuxVkTquY0J01 WCmwt/ewf58/duMqTFgzOidkw0gjQMIiclqJzKDbCwBwK304VeCqX19HaGG9SLwvTjBvs64hDcDom Ve7nkdZw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1lxtQ3-003BkT-Qc; Mon, 28 Jun 2021 15:43:41 +0000 Date: Mon, 28 Jun 2021 16:43:31 +0100 From: Matthew Wilcox To: Christoph Hellwig Cc: akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 27/46] mm/writeback: Add __folio_mark_dirty() Message-ID: References: <20210622121551.3398730-1-willy@infradead.org> <20210622121551.3398730-28-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 28, 2021 at 07:03:26AM +0100, Christoph Hellwig wrote: > On Thu, Jun 24, 2021 at 07:37:30PM +0100, Matthew Wilcox wrote: > > On Wed, Jun 23, 2021 at 11:27:12AM +0200, Christoph Hellwig wrote: > > > On Tue, Jun 22, 2021 at 01:15:32PM +0100, Matthew Wilcox (Oracle) wrote: > > > > Turn __set_page_dirty() into a wrapper around __folio_mark_dirty() (which > > > > can directly cast from page to folio because we know that set_page_dirty() > > > > calls filesystems with the head page). Convert account_page_dirtied() > > > > into folio_account_dirtied() and account the number of pages in the folio. > > > > > > Is it really worth micro-optimizing a transitional function like that? > > > I'd rather eat the overhead of the compound_page() call over adding hacky > > > casts like this. > > > > Fair enough. There's only three calls to it and one of them goes away > > this series. > > The other option would be a helper that asserts a page is not a tail > page and then do the cast to document the assumptions. btw, every call to folio_flags() checks !PageTail: struct page *page = &folio->page; VM_BUG_ON_PGFLAGS(PageTail(page), page); now, that's not going to be turned on for regular builds, but it does give us a _lot_ of runtime assertions that somebody hasn't cast a tail page to a folio.