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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 97C78C433E0 for ; Wed, 17 Mar 2021 14:13:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A35D64F69 for ; Wed, 17 Mar 2021 14:13:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231308AbhCQOMg (ORCPT ); Wed, 17 Mar 2021 10:12:36 -0400 Received: from mx2.suse.de ([195.135.220.15]:49300 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231458AbhCQOMb (ORCPT ); Wed, 17 Mar 2021 10:12:31 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1615990350; 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=aAUcDe4pvPLn4fC/tremYQrLTY4DcLiLDV9Wbabr0yI=; b=qNXoN1DKzjDs4kcMcCP/zoOlx/Kirf7ZUCuEqfN4VYQZULteWQVKHEH2MhKdOSTNaW1oVI mDPKxwGzmFNTsRmdmY4LwnIT06xCAookjzKr0fgdOWF+YD0gTjuKarNw39oe0+T5wCyoNS MUGbIBtvsjgWCb18AeOV7UmI2TZ94dU= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 20616AC47; Wed, 17 Mar 2021 14:12:30 +0000 (UTC) Date: Wed, 17 Mar 2021 15:12:29 +0100 From: Michal Hocko To: Oscar Salvador Cc: Andrew Morton , Vlastimil Babka , David Hildenbrand , Muchun Song , Mike Kravetz , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 2/5] mm,compaction: Let isolate_migratepages_{range,block} return error codes Message-ID: References: <20210317111251.17808-1-osalvador@suse.de> <20210317111251.17808-3-osalvador@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210317111251.17808-3-osalvador@suse.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 17-03-21 12:12:48, Oscar Salvador wrote: > Currently, isolate_migratepages_{range,block} and their callers use > a pfn == 0 vs pfn != 0 scheme to let the caller know whether there was > any error during isolation. > This does not work as soon as we need to start reporting different error > codes and make sure we pass them down the chain, so they are properly > interpreted by functions like e.g: alloc_contig_range. > > Let us rework isolate_migratepages_{range,block} so we can report error > codes. Yes this is an improvement. > Since isolate_migratepages_block will stop returning the next pfn to be > scanned, we reuse the cc->migrate_pfn field to keep track of that. This looks hakish and I cannot really tell that users of cc->migrate_pfn work as intended. > @@ -810,6 +811,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, > unsigned long next_skip_pfn = 0; > bool skip_updated = false; > > + cc->migrate_pfn = low_pfn; > + > /* > * Ensure that there are not too many pages isolated from the LRU > * list by either parallel reclaimers or compaction. If there are, > @@ -818,16 +821,16 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, > while (unlikely(too_many_isolated(pgdat))) { > /* stop isolation if there are still pages not migrated */ > if (cc->nr_migratepages) > - return 0; > + return -EINTR; > > /* async migration should just abort */ > if (cc->mode == MIGRATE_ASYNC) > - return 0; > + return -EINTR; EINTR for anything other than signal based bail out is really confusing. -- Michal Hocko SUSE Labs