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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57A5AC433F5 for ; Mon, 7 Mar 2022 01:21:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BFDF68D0002; Sun, 6 Mar 2022 20:21:26 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BACA18D0001; Sun, 6 Mar 2022 20:21:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A74A58D0002; Sun, 6 Mar 2022 20:21:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.25]) by kanga.kvack.org (Postfix) with ESMTP id 982A08D0001 for ; Sun, 6 Mar 2022 20:21:26 -0500 (EST) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 7153861709 for ; Mon, 7 Mar 2022 01:21:26 +0000 (UTC) X-FDA: 79215837372.11.0D19005 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf03.hostedemail.com (Postfix) with ESMTP id E09A020002 for ; Mon, 7 Mar 2022 01:21:25 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 08410B80EFB; Mon, 7 Mar 2022 01:21:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F295BC340EC; Mon, 7 Mar 2022 01:21:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1646616082; bh=h83Y33RF7oFYfMTjMpePiE2v5flGLBtPS3zZbf52cOo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NWQJGLCKb+iiOovlBpY9pafpCo06Ang51RY1NmaoMBmkPNgSpYpRIh/VPU02fadYd 82ZDQDSX8ltQ9XqWZQ8px4dJLXRyeeyb+N61P0Pnc4tg64GSaZvUDUZwBh3WL8ji49 y/h7H9b0WFCwWGiS6qvvxSIQXkOy9oLlCuAn4HiE= Date: Sun, 6 Mar 2022 17:21:21 -0800 From: Andrew Morton To: Miaohe Lin Cc: , , , , , , , , , , , , , , , , , Subject: Re: [PATCH 10/16] mm/migration: remove PG_writeback handle in folio_migrate_flags Message-Id: <20220306172121.50d00e8b328a6bd1dea91ee7@linux-foundation.org> In-Reply-To: <20220304093409.25829-11-linmiaohe@huawei.com> References: <20220304093409.25829-1-linmiaohe@huawei.com> <20220304093409.25829-11-linmiaohe@huawei.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: 8xtkdh4z641bz8sky1d6gef18qzintsq Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=NWQJGLCK; spf=pass (imf03.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Rspamd-Queue-Id: E09A020002 X-HE-Tag: 1646616085-942239 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 4 Mar 2022 17:34:03 +0800 Miaohe Lin wrote: > When newfolio reaches here, it's guaranteed that PG_writeback is not set > because caller ensures writeback must have been completed. Remove this > unneeded check and cleanup the relevant comment. What guarantees that writeback cannot start after the caller has checked? I see no such check in iomap_migrate_page()? > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -549,18 +549,6 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio) > if (!folio_test_hugetlb(folio)) > folio->private = NULL; > > - /* > - * If any waiters have accumulated on the new page then > - * wake them up. > - */ > - if (folio_test_writeback(newfolio)) > - folio_end_writeback(newfolio); > - > - /* > - * PG_readahead shares the same bit with PG_reclaim. The above > - * end_page_writeback() may clear PG_readahead mistakenly, so set the > - * bit after that. > - */ > if (folio_test_readahead(folio)) > folio_set_readahead(newfolio); > folio_migrate_flags() and folio_migrate_copy() are global, export-to-modules functions but have no interface documentation. That was bad of us. I wonder why those two functions are exported to modules anyway.