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=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E4709C433FE for ; Thu, 10 Dec 2020 14:17:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A07E323CD4 for ; Thu, 10 Dec 2020 14:17:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389739AbgLJORB (ORCPT ); Thu, 10 Dec 2020 09:17:01 -0500 Received: from mx2.suse.de ([195.135.220.15]:35140 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389607AbgLJOQu (ORCPT ); Thu, 10 Dec 2020 09:16:50 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2CC44AE95; Thu, 10 Dec 2020 14:16:04 +0000 (UTC) Date: Thu, 10 Dec 2020 15:15:47 +0100 From: Oscar Salvador To: Muchun Song Cc: corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, rdunlap@infradead.org, oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, almasrymina@google.com, rientjes@google.com, willy@infradead.org, mhocko@suse.com, song.bao.hua@hisilicon.com, david@redhat.com, duanxiongchun@bytedance.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v8 03/12] mm/bootmem_info: Introduce free_bootmem_page helper Message-ID: <20201210141547.GA8538@localhost.localdomain> References: <20201210035526.38938-1-songmuchun@bytedance.com> <20201210035526.38938-4-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201210035526.38938-4-songmuchun@bytedance.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 10, 2020 at 11:55:17AM +0800, Muchun Song wrote: > Any memory allocated via the memblock allocator and not via the buddy > will be makred reserved already in the memmap. For those pages, we can marked > call free_bootmem_page() to free it to buddy allocator. > > Becasue we wan to free some vmemmap pages of the HugeTLB to the buddy Because want > allocator, we can use this helper to do that in the later patchs. patches To be honest, I think if would be best to introduce this along with patch#4, so we get to see where it gets used. > Signed-off-by: Muchun Song > --- > include/linux/bootmem_info.h | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/include/linux/bootmem_info.h b/include/linux/bootmem_info.h > index 4ed6dee1adc9..20a8b0df0c39 100644 > --- a/include/linux/bootmem_info.h > +++ b/include/linux/bootmem_info.h > @@ -3,6 +3,7 @@ > #define __LINUX_BOOTMEM_INFO_H > > #include > +#include already includes > +static inline void free_bootmem_page(struct page *page) > +{ > + unsigned long magic = (unsigned long)page->freelist; > + > + /* bootmem page has reserved flag in the reserve_bootmem_region */ reserve_bootmem_region sets the reserved flag on bootmem pages? > + VM_WARN_ON(!PageReserved(page) || page_ref_count(page) != 2); We do check for PageReserved in patch#4 before calling in here. Do we need yet another check here? IOW, do we need to be this paranoid? > + if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) > + put_page_bootmem(page); > + else > + WARN_ON(1); Lately, some people have been complaining about using WARN_ON as some systems come with panic_on_warn set. I would say that in this case it does not matter much as if the vmemmap pages are not either SECTION_INFO or MIX_SECTION_INFO it means that a larger corruption happened elsewhere. But I think I would align the checks here. It does not make sense to me to only scream under DEBUG_VM if page's refcount differs from 2, and have a WARN_ON if the page we are trying to free was not used for the memmap array. Both things imply a corruption, so I would set the checks under the same configurations. -- Oscar Salvador SUSE L3