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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8C43AC7618E for ; Mon, 24 Apr 2023 10:54:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231240AbjDXKyU (ORCPT ); Mon, 24 Apr 2023 06:54:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40582 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230185AbjDXKyS (ORCPT ); Mon, 24 Apr 2023 06:54:18 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0079B4 for ; Mon, 24 Apr 2023 03:54:16 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 5F20C21852; Mon, 24 Apr 2023 10:54:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1682333655; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=hwTuvG4SizdTPKkmhS98O1meDh9fxreSFtv1kR4Jui0=; b=fIjQRdSlTKFT7T3QRNKg1BumJNEq9wbTY9Uj50hocW2GDWD2+0gv4B8ZZtXeboIkse+tR4 9+eIbDfpBsBKwslZVLkd2ih6uV7VDc/zZ4tolCkkevrv0ZCUxfqyMqkTc67KEYPKQqzILI eKXyDPcdTym8Atfq/r5O8kW25NktviI= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 4424F13780; Mon, 24 Apr 2023 10:54:15 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id TwDYDddfRmTFPgAAMHmgww (envelope-from ); Mon, 24 Apr 2023 10:54:15 +0000 Date: Mon, 24 Apr 2023 12:54:14 +0200 From: Michal Hocko To: Baolin Wang Cc: akpm@linux-foundation.org, rppt@kernel.org, ying.huang@intel.com, mgorman@techsingularity.net, vbabka@suse.cz, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] mm/page_alloc: drop the unnecessary pfn_valid() for start pfn Message-ID: References: <9fc85cce8908938f4fd75ff50bc981c073779aa5.1682229876.git.baolin.wang@linux.alibaba.com> <7525a9f6-b431-4404-2878-898e52905d4a@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7525a9f6-b431-4404-2878-898e52905d4a@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 24-04-23 18:46:40, Baolin Wang wrote: > > > On 4/24/2023 5:50 PM, Michal Hocko wrote: > > On Sun 23-04-23 18:59:10, Baolin Wang wrote: > > > We've already used pfn_to_online_page() for start pfn to make sure > > > > Who is we? I do not see any note explicitly requiring that start_pfn has > > to be valid for __pageblock_pfn_to_page. > > Sorry for confusing, what I mean is the __pageblock_pfn_to_page() function, > which has used pfn_to_online_page() for start pfn. So the pfn_valid() in > __pageblock_pfn_to_page() for start pfn is unnecessary. > > I will update the commit log to make it clear. Your comment suggested that the check _has_ already been done. Which is not the case. pfn_to_online_page is called later in the function so I guess you should rephrase as following: " __pageblock_pfn_to_page currently performs both pfn_valid check and pfn_to_online_page. The former one is redundant because the latter is a stronger check. Drop pfn_valid. " With that or something going along with that. Feel free to add Acked-by: Michal Hocko > > > it is online and valid, so the pfn_valid() for the start pfn is > > > unnecessary, drop it. > > > > > > Signed-off-by: Baolin Wang > > > Reviewed-by: David Hildenbrand > > > Reviewed-by: "Huang, Ying" > > > --- > > > Changes from v1: > > > - Collect reviewed tags. Thanks David and Ying. > > > --- > > > mm/page_alloc.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > index 9de2a18519a1..6457b64fe562 100644 > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -1512,7 +1512,7 @@ struct page *__pageblock_pfn_to_page(unsigned long start_pfn, > > > /* end_pfn is one past the range we are checking */ > > > end_pfn--; > > > - if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) > > > + if (!pfn_valid(end_pfn)) > > > return NULL; > > > start_page = pfn_to_online_page(start_pfn); > > > -- > > > 2.27.0 > > -- Michal Hocko SUSE Labs