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[209.132.183.28]) by mx.google.com with ESMTPS id n37si39643209qte.331.2019.08.01.07.45.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Aug 2019 07:45:05 -0700 (PDT) Received-SPF: pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8FDD5B2DF0; Thu, 1 Aug 2019 14:45:04 +0000 (UTC) Received: from [10.36.116.115] (ovpn-116-115.ams2.redhat.com [10.36.116.115]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3C3826012D; Thu, 1 Aug 2019 14:45:02 +0000 (UTC) Subject: Re: [PATCH v3 3/5] mm,sparse: Add SECTION_USE_VMEMMAP flag To: Oscar Salvador , akpm@linux-foundation.org Cc: dan.j.williams@intel.com, pasha.tatashin@soleen.com, mhocko@suse.com, anshuman.khandual@arm.com, Jonathan.Cameron@huawei.com, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20190725160207.19579-1-osalvador@suse.de> <20190725160207.19579-4-osalvador@suse.de> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190725160207.19579-4-osalvador@suse.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Thu, 01 Aug 2019 14:45:04 +0000 (UTC) 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 25.07.19 18:02, Oscar Salvador wrote: > When hot-removing memory, we need to be careful about two things: > > 1) Memory range must be memory_block aligned. This is what > check_hotplug_memory_range() checks for. > > 2) If a range was hot-added using MHP_MEMMAP_ON_MEMORY, we need to check > whether the caller is removing memory with the same granularity that > it was added. The second step does only apply to MMAP_ON_MEMORY and is not universally true. > > So to check against case 2), we mark all sections used by vmemmap > (not only the ones containing vmemmap pages, but all sections spanning > the memory range) with SECTION_USE_VMEMMAP. SECTION_USE_VMEMAP is misleding. Rather SECTION_MMAP_ON_MEMORY (TBD). Please *really* add a description (these sections) > > This will allow us to do some sanity checks when in hot-remove stage. > One idea: lookup the struct page of the lowest memory address you are removing and test if it lies on a PageVmemmap(). Then, from the stored info along the vmemmap page (start + length) you can test if all memory the vmemmap is responsible for is removed. This should work or am I missing something? > Signed-off-by: Oscar Salvador > --- > include/linux/memory_hotplug.h | 3 ++- > include/linux/mmzone.h | 8 +++++++- > mm/memory_hotplug.c | 2 +- > mm/sparse.c | 9 +++++++-- > 4 files changed, 17 insertions(+), 5 deletions(-) > > diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h > index 45dece922d7c..6b20008d9297 100644 > --- a/include/linux/memory_hotplug.h > +++ b/include/linux/memory_hotplug.h > @@ -366,7 +366,8 @@ extern void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn, > unsigned long nr_pages, struct vmem_altmap *altmap); > extern bool is_memblock_offlined(struct memory_block *mem); > extern int sparse_add_section(int nid, unsigned long pfn, > - unsigned long nr_pages, struct vmem_altmap *altmap); > + unsigned long nr_pages, struct vmem_altmap *altmap, > + bool vmemmap_section); > extern void sparse_remove_section(struct mem_section *ms, > unsigned long pfn, unsigned long nr_pages, > unsigned long map_offset, struct vmem_altmap *altmap); > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index d77d717c620c..259c326962f5 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -1254,7 +1254,8 @@ extern size_t mem_section_usage_size(void); > #define SECTION_HAS_MEM_MAP (1UL<<1) > #define SECTION_IS_ONLINE (1UL<<2) > #define SECTION_IS_EARLY (1UL<<3) > -#define SECTION_MAP_LAST_BIT (1UL<<4) > +#define SECTION_USE_VMEMMAP (1UL<<4) > +#define SECTION_MAP_LAST_BIT (1UL<<5) > #define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1)) > #define SECTION_NID_SHIFT 3 > > @@ -1265,6 +1266,11 @@ static inline struct page *__section_mem_map_addr(struct mem_section *section) > return (struct page *)map; > } > > +static inline int vmemmap_section(struct mem_section *section) > +{ > + return (section && (section->section_mem_map & SECTION_USE_VMEMMAP)); > +} > + > static inline int present_section(struct mem_section *section) > { > return (section && (section->section_mem_map & SECTION_MARKED_PRESENT)); > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 3d97c3711333..c2338703ce80 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -314,7 +314,7 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages, > > pfns = min(nr_pages, PAGES_PER_SECTION > - (pfn & ~PAGE_SECTION_MASK)); > - err = sparse_add_section(nid, pfn, pfns, altmap); > + err = sparse_add_section(nid, pfn, pfns, altmap, 0); > if (err) > break; > pfn += pfns; > diff --git a/mm/sparse.c b/mm/sparse.c > index 79355a86064f..09cac39e39d9 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -856,13 +856,18 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn, > * * -ENOMEM - Out of memory. > */ > int __meminit sparse_add_section(int nid, unsigned long start_pfn, > - unsigned long nr_pages, struct vmem_altmap *altmap) > + unsigned long nr_pages, struct vmem_altmap *altmap, > + bool vmemmap_section) > { > unsigned long section_nr = pfn_to_section_nr(start_pfn); > + unsigned long flags = 0; > struct mem_section *ms; > struct page *memmap; > int ret; > > + if (vmemmap_section) > + flags = SECTION_USE_VMEMMAP; > + > ret = sparse_index_init(section_nr, nid); > if (ret < 0) > return ret; > @@ -884,7 +889,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, > /* Align memmap to section boundary in the subsection case */ > if (section_nr_to_pfn(section_nr) != start_pfn) > memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr)); > - sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0); > + sparse_init_one_section(ms, section_nr, memmap, ms->usage, flags); > > return 0; > } > -- Thanks, David / dhildenb