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Tue, 6 Apr 2021 15:32:44 +0000 (UTC) Subject: Re: [PATCH v6 2/8] mm,memory_hotplug: Relax fully spanned sections check To: Oscar Salvador , Andrew Morton Cc: Michal Hocko , Anshuman Khandual , Pavel Tatashin , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210406111115.8953-1-osalvador@suse.de> <20210406111115.8953-3-osalvador@suse.de> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Tue, 6 Apr 2021 17:32:43 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210406111115.8953-3-osalvador@suse.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 3BE0440002C2 X-Stat-Signature: x6gcezqc54ubib1xuyn3ftmaa6ndps19 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf02; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=216.205.24.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617723177-959494 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 06.04.21 13:11, Oscar Salvador wrote: > When using self-hosted vmemmap pages, the number of pages passed to > {online,offline}_pages might not fully span sections, but they always > fully span pageblocks. > Relax the check account for that case. > > Signed-off-by: Oscar Salvador > --- > mm/memory_hotplug.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 0cdbbfbc5757..5fe3e3942b19 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -838,9 +838,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, > int ret; > struct memory_notify arg; > > - /* We can only online full sections (e.g., SECTION_IS_ONLINE) */ > + /* We can only offline full sections (e.g., SECTION_IS_ONLINE). > + * However, when using e.g: memmap_on_memory, some pages are initialized > + * prior to calling in here. The remaining amount of pages must be > + * pageblock aligned. > + */ > if (WARN_ON_ONCE(!nr_pages || > - !IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION))) > + !IS_ALIGNED(pfn | nr_pages, pageblock_nr_pages))) > return -EINVAL; > > mem_hotplug_begin(); > @@ -1573,9 +1577,13 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages) > int ret, node; > char *reason; > > - /* We can only offline full sections (e.g., SECTION_IS_ONLINE) */ > + /* We can only offline full sections (e.g., SECTION_IS_ONLINE). > + * However, when using e.g: memmap_on_memory, some pages are initialized > + * prior to calling in here. The remaining amount of pages must be > + * pageblock aligned. > + */ > if (WARN_ON_ONCE(!nr_pages || > - !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION))) > + !IS_ALIGNED(start_pfn | nr_pages, pageblock_nr_pages))) > return -EINVAL; > > mem_hotplug_begin(); > I'd only relax start_pfn. That way the function is pretty much impossible to abuse for sub-section onlining/offlining. if (WARN_ON_ONCE(!nr_pages || !IS_ALIGNED(start_pfn, pageblock_nr_pages)) !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION))) -- Thanks, David / dhildenb