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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 804D0C4338F for ; Thu, 5 Aug 2021 15:17:53 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 09A3960EEA for ; Thu, 5 Aug 2021 15:17:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 09A3960EEA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 7FAE58D0001; Thu, 5 Aug 2021 11:17:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7AAE96B0071; Thu, 5 Aug 2021 11:17:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6994C8D0001; Thu, 5 Aug 2021 11:17:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0136.hostedemail.com [216.40.44.136]) by kanga.kvack.org (Postfix) with ESMTP id 4D3926B006C for ; Thu, 5 Aug 2021 11:17:52 -0400 (EDT) Received: from smtpin34.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id EE96E252D6 for ; Thu, 5 Aug 2021 15:17:51 +0000 (UTC) X-FDA: 78441381942.34.7DB785D Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf29.hostedemail.com (Postfix) with ESMTP id 3F10090025AC for ; Thu, 5 Aug 2021 15:17:50 +0000 (UTC) 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=njZhkvm1vyJvdD0r+JCFjqmWiHQO4/apHfiulTdyXJI=; b=PRcDxoejEV9jYOj6oe78EgM76L mAUuIEsgbKHv8HqWpnZmclwDlhhw8HtvbgXyXlYXjgvBBmTDUpFNdb5EIEXioRGBKDyOOSnf3mpRA KXQ/KckJDjZ4WpxhmO5NIBXP+zgAe6uiF5pAvgCEyw5rbwj6GxBFDYASwRaFx7p6glkrHESLQ6WNq Mq8xhK0qHAYtQt3wDRnIrueWZWY4gbBJaKM8uTfs9v7LM/U89NP+WskNL3GcKAkP+Zshwz4+g+z5i 1zS/C/xw3fozgR4/v2j14gq2IlYce9P6v3Q9mEOFfNB0K9pvHvppIywIe/Gjo7VBlZNb593spN3PI FZBeUXFw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mBf7n-007Cmc-3r; Thu, 05 Aug 2021 15:17:38 +0000 Date: Thu, 5 Aug 2021 16:17:35 +0100 From: Matthew Wilcox To: Baolin Wang Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/5] mm: migrate: Move the page count validation to the proper place Message-ID: References: <1f7e1d083864fbb17a20a9c8349d2e8b427e20a3.1628174413.git.baolin.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1f7e1d083864fbb17a20a9c8349d2e8b427e20a3.1628174413.git.baolin.wang@linux.alibaba.com> Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=PRcDxoej; dmarc=none; spf=none (imf29.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org X-Stat-Signature: 3fwkgejxyu8mr9tqkjkq1bnxrfauxdbe X-Rspamd-Queue-Id: 3F10090025AC X-Rspamd-Server: rspam01 X-HE-Tag: 1628176670-580527 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 Thu, Aug 05, 2021 at 11:05:56PM +0800, Baolin Wang wrote: > We've got the expected count for anonymous page or file page by > expected_page_refs() at the beginning of migrate_page_move_mapping(), > thus we should move the page count validation a little forward to > reduce duplicated code. Please add an explanation to the changelog for why it's safe to pull this out from under the i_pages lock. > Signed-off-by: Baolin Wang > --- > mm/migrate.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 239b238..5559571 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -386,11 +386,10 @@ int folio_migrate_mapping(struct address_space *mapping, > int expected_count = expected_page_refs(mapping, &folio->page) + extra_count; > long nr = folio_nr_pages(folio); > > - if (!mapping) { > - /* Anonymous page without mapping */ > - if (folio_ref_count(folio) != expected_count) > - return -EAGAIN; > + if (folio_ref_count(folio) != expected_count) > + return -EAGAIN; > > + if (!mapping) { > /* No turning back from here */ > newfolio->index = folio->index; > newfolio->mapping = folio->mapping; > @@ -404,8 +403,7 @@ int folio_migrate_mapping(struct address_space *mapping, > newzone = folio_zone(newfolio); > > xas_lock_irq(&xas); > - if (folio_ref_count(folio) != expected_count || > - xas_load(&xas) != folio) { > + if (xas_load(&xas) != folio) { > xas_unlock_irq(&xas); > return -EAGAIN; > } > -- > 1.8.3.1 > >