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 D8EB8C433F5 for ; Thu, 9 Dec 2021 13:03:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4DAE26B0071; Thu, 9 Dec 2021 08:02:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 48BD86B0073; Thu, 9 Dec 2021 08:02:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 353FE6B0074; Thu, 9 Dec 2021 08:02:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0168.hostedemail.com [216.40.44.168]) by kanga.kvack.org (Postfix) with ESMTP id 286136B0071 for ; Thu, 9 Dec 2021 08:02:57 -0500 (EST) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id D279C8248076 for ; Thu, 9 Dec 2021 13:02:46 +0000 (UTC) X-FDA: 78898270332.19.43D769C Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf20.hostedemail.com (Postfix) with ESMTP id 706C11C0009 for ; Thu, 9 Dec 2021 13:02:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1639054965; h=from:from:reply-to:subject:subject: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=7UP4nzdzXQnGWZmCcFZX+JugsVQelS/63DjQeD65Ya8=; b=WPfhEXzRz+xhp5IaQ21FccRv9aRP5o2LaWEC3FnQiQuZTFEbZ9Gbd8goj4h1WtfAPZvMxW CBiPIH2r2MWLZTdxBBnvLRePNpoPXcE3WZtVyo/FP68y8nMwmvnlt7kdHJAc/fz/apPy2y 4yNeG5rqZKrBoP4sVM3i3of1ve8waTQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-310-v2AeLTDrPKK_kDEjnRtj-w-1; Thu, 09 Dec 2021 08:02:42 -0500 X-MC-Unique: v2AeLTDrPKK_kDEjnRtj-w-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 42D846123C; Thu, 9 Dec 2021 13:02:39 +0000 (UTC) Received: from localhost (ovpn-13-171.pek2.redhat.com [10.72.13.171]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3A2D35E272; Thu, 9 Dec 2021 13:02:12 +0000 (UTC) Date: Thu, 9 Dec 2021 21:02:10 +0800 From: Baoquan He To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, hch@lst.de, robin.murphy@arm.com, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, vbabka@suse.cz, m.szyprowski@samsung.com, John.p.donnelly@oracle.com, kexec@lists.infradead.org Subject: Re: [PATCH RESEND v2 3/5] mm_zone: add function to check if managed dma zone exists Message-ID: <20211209130210.GB3050@MiWiFi-R3L-srv> References: <20211207030750.30824-1-bhe@redhat.com> <20211207030750.30824-4-bhe@redhat.com> <0a9bc228-21ba-abe3-d9c8-b9d52b936366@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0a9bc228-21ba-abe3-d9c8-b9d52b936366@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=WPfhEXzR; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf20.hostedemail.com: domain of bhe@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=bhe@redhat.com X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 706C11C0009 X-Stat-Signature: ogr3fith674t3zbxs3uc3ppwsomg1q7t X-HE-Tag: 1639054966-990485 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 12/07/21 at 12:23pm, David Hildenbrand wrote: > On 07.12.21 04:07, Baoquan He wrote: > > In some places of the current kernel, it assumes that dma zone must have > > managed pages if CONFIG_ZONE_DMA is enabled. While this is not always true. > > E.g in kdump kernel of x86_64, only low 1M is presented and locked down > > at very early stage of boot, so that there's no managed pages at all in > > DMA zone. This exception will always cause page allocation failure if page > > is requested from DMA zone. > > > > Here add function has_managed_dma() and the relevant helper functions to > > check if there's DMA zone with managed pages. It will be used in later > > patches. > > > > Signed-off-by: Baoquan He > > --- > > include/linux/mmzone.h | 21 +++++++++++++++++++++ > > mm/page_alloc.c | 11 +++++++++++ > > 2 files changed, 32 insertions(+) > > > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > > index 58e744b78c2c..82d23e13e0e5 100644 > > --- a/include/linux/mmzone.h > > +++ b/include/linux/mmzone.h > > @@ -998,6 +998,18 @@ static inline bool zone_is_zone_device(struct zone *zone) > > } > > #endif > > > > +#ifdef CONFIG_ZONE_DMA > > +static inline bool zone_is_dma(struct zone *zone) > > +{ > > + return zone_idx(zone) == ZONE_DMA; > > +} > > +#else > > +static inline bool zone_is_dma(struct zone *zone) > > +{ > > + return false; > > +} > > +#endif > > + > > /* > > * Returns true if a zone has pages managed by the buddy allocator. > > * All the reclaim decisions have to use this function rather than > > @@ -1046,6 +1058,7 @@ static inline int is_highmem_idx(enum zone_type idx) > > #endif > > } > > > > +bool has_managed_dma(void); > > /** > > * is_highmem - helper function to quickly check if a struct zone is a > > * highmem zone or not. This is an attempt to keep references > > @@ -1131,6 +1144,14 @@ extern struct zone *next_zone(struct zone *zone); > > ; /* do nothing */ \ > > else > > > > +#define for_each_managed_zone(zone) \ > > + for (zone = (first_online_pgdat())->node_zones; \ > > + zone; \ > > + zone = next_zone(zone)) \ > > + if (!managed_zone(zone)) \ > > + ; /* do nothing */ \ > > + else > > + > > static inline struct zone *zonelist_zone(struct zoneref *zoneref) > > { > > return zoneref->zone; > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index c5952749ad40..ac0ea42a4e5f 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -9459,4 +9459,15 @@ bool take_page_off_buddy(struct page *page) > > spin_unlock_irqrestore(&zone->lock, flags); > > return ret; > > } > > + > > +bool has_managed_dma(void) > > +{ > > + struct zone *zone; > > + > > + for_each_managed_zone(zone) { > > + if (zone_is_dma(zone)) > > + return true; > > + } > > + return false; > > +} > > Wouldn't it be "easier/faster" to just iterate online nodes and directly > obtain the ZONE_DMA, checking if there are managed pages? Thanks, Dave. Please check for_each_managed_zone(), it is iterating online nodes and it's each managed zone. Is below what you are suggesting? The only difference is I introduced for_each_managed_zone() which can be reused later if needed. Not sure if I got your suggestion correctly. bool has_managed_dma(void) { struct pglist_data *pgdat; struct zone *zone; enum zone_type i, j; for_each_online_pgdat(pgdat) { for (i = 0; i < MAX_NR_ZONES - 1; i++) { struct zone *zone = &pgdat->node_zones[i]; if (zone_is_dma(zone)) return true; } } return false; }