From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
Received: from vger.kernel.org (vger.kernel.org [23.128.96.18])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 05843C4332F
	for <linux-kernel@archiver.kernel.org>; Tue, 13 Dec 2022 14:35:05 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S235396AbiLMOfD (ORCPT <rfc822;linux-kernel@archiver.kernel.org>);
        Tue, 13 Dec 2022 09:35:03 -0500
Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55134 "EHLO
        lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S229787AbiLMOfA (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 13 Dec 2022 09:35:00 -0500
Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1])
        by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 63818C06
        for <linux-kernel@vger.kernel.org>; Tue, 13 Dec 2022 06:34:59 -0800 (PST)
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=Bp1NI5NxRf5KPduMUan4tguo3EwGdbgGIpn9oy21c2M=; b=Z9y1G33QX5Kj1ZxByLC52j2sGN
        t/6SEShZ/322yWKWHyaUh1MxwCUY7jL8NnetYR/Xs30mEgxSsMIfdbnc/kIx6/4sN4LFygtPjW4AG
        hvedfDFbtVQGaeH7S1fkBKv4y1c3c0aqesi5yxUK9HTKPvKGHYO/24pRLfLcEySQJcREDVC6FYN1q
        3HJlIUofmcFw/kJojLFvMuhhWR/IKO1Bz6pofhWoyYQAZPU6PH6Fp0MTDmfUN8njxQfYEfsxhs/9/
        N5ONc6nOw92WqGncQ8iciGN1uUMMJuKFx6+zVuvSRjXJOjtOLkqiSrDvpXzgQO5WeoEgAe1EpBAgS
        OQZdpXbQ==;
Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux))
        id 1p56Mq-00CIsd-V2; Tue, 13 Dec 2022 14:34:49 +0000
Date:   Tue, 13 Dec 2022 14:34:48 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Kefeng Wang <wangkefeng.wang@huawei.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        David Hildenbrand <david@redhat.com>,
        Oscar Salvador <osalvador@suse.de>,
        SeongJae Park <sj@kernel.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, damon@lists.linux.dev,
        vishal.moola@gmail.com
Subject: Re: [PATCH -next 2/8] mm: page_idle: Convert page idle to use folios
Message-ID: <Y5iNiNUoNlupyhow@casper.infradead.org>
References: <20221213092735.187924-1-wangkefeng.wang@huawei.com>
 <20221213092735.187924-3-wangkefeng.wang@huawei.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20221213092735.187924-3-wangkefeng.wang@huawei.com>
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Dec 13, 2022 at 05:27:29PM +0800, Kefeng Wang wrote:
> -static struct page *page_idle_get_page(unsigned long pfn)
> +static struct folio *folio_idle_get_folio(unsigned long pfn)
>  {
> -	struct page *page = pfn_to_online_page(pfn);
> +	struct folio *folio = pfn_to_online_folio(pfn);
>  
> -	if (!page || !PageLRU(page) ||
> -	    !get_page_unless_zero(page))
> +	if (!folio || !folio_test_lru(folio) || !folio_try_get(folio))
>  		return NULL;

You've changed the semantics here, and I suspect will cause breakage
as a result.  Before if you called page_idle_get_page() on a tail page,
you got a NULL pointer returned.  Now you get the folio that contains
that tail page.

I think you have to continue to call pfn_to_online_page() and do
the conversion to folio manually in this function.  By all means
convert this function to return the folio, but you need to take a
little more care.