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Thu, 25 Mar 2021 16:55:40 +0000 (UTC) Received: from [10.36.115.72] (ovpn-115-72.ams2.redhat.com [10.36.115.72]) by smtp.corp.redhat.com (Postfix) with ESMTP id 862AA5D736; Thu, 25 Mar 2021 16:55:38 +0000 (UTC) Subject: Re: [PATCH v5 1/5] mm,memory_hotplug: Allocate memmap from the added memory range To: Michal Hocko Cc: Oscar Salvador , Andrew Morton , Anshuman Khandual , Vlastimil Babka , Pavel Tatashin , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <062bc5d7-a83c-1c1a-7b77-9f043643f4fa@redhat.com> <31c3e6f7-f631-7b00-2c33-518b0f24a75f@redhat.com> <40fac999-2d28-9205-23f0-516fa9342bbe@redhat.com> <92fe19d0-56ac-e929-a9c1-d6a4e0da39d1@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <17e666ec-93ae-c0f3-47cf-67e8a6df6afc@redhat.com> Date: Thu, 25 Mar 2021 17:55:37 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25.03.21 17:47, Michal Hocko wrote: > On Thu 25-03-21 17:36:22, Michal Hocko wrote: >> If all it takes is to make pfn_to_online_page work (and my >> previous attempt is incorrect because it should consult block rather >> than section pfn range) > > This should work. > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index 9697acfe96eb..e50d685be8ab 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -510,6 +510,23 @@ static struct memory_block *find_memory_block_by_id(unsigned long block_id) > return mem; > } > > +struct page *is_vmemmap_page(unsigned long pfn) > +{ > + unsigned long nr = pfn_to_section_nr(pfn); > + struct memory_block *mem; > + unsigned long block_pfn; > + > + mem = find_memory_block_by_id(memory_block_id(nr)); > + if (!mem || !mem->nr_vmemmap_pages) > + return NULL; > + > + block_pfn = section_nr_to_pfn(mem->start_section_nr); > + if (pfn - block_pfn > mem->nr_vmemmap_pages) > + return NULL; > + > + return pfn_to_page(pfn); > +} > + > /* > * Called under device_hotplug_lock. > */ > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 754026a9164d..760bf3ad48d5 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -304,8 +304,16 @@ struct page *pfn_to_online_page(unsigned long pfn) > return NULL; > > ms = __nr_to_section(nr); > - if (!online_section(ms)) > + if (!online_section(ms)) { > + /* > + * vmemmap reserved space can eat up a whole section which then > + * never gets onlined because it doesn't contain any memory to > + * online. > + */ > + if (memmap_on_memory) > + return is_vmemmap_page(pfn); > return NULL; > + } > > /* > * Save some code text when online_section() + > It should take care of discussed zone shrinking as well, at least as long as the granularity is not smaller than sub-sections. -- Thanks, David / dhildenb