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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 14 Jun 2019 17:26:04 +0100 Received: from b03ledav001.gho.boulder.ibm.com (b03ledav001.gho.boulder.ibm.com [9.17.130.232]) by b03cxnp08028.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5EGQ3M135520844 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 14 Jun 2019 16:26:04 GMT Received: from b03ledav001.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DD7196E04E; Fri, 14 Jun 2019 16:26:03 +0000 (GMT) Received: from b03ledav001.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8F72F6E052; Fri, 14 Jun 2019 16:26:01 +0000 (GMT) Received: from [9.199.60.77] (unknown [9.199.60.77]) by b03ledav001.gho.boulder.ibm.com (Postfix) with ESMTP; Fri, 14 Jun 2019 16:26:01 +0000 (GMT) Subject: Re: [PATCH -next] mm/hotplug: skip bad PFNs from pfn_to_online_page() To: Dan Williams Cc: Oscar Salvador , Qian Cai , Andrew Morton , Linux MM , Linux Kernel Mailing List , jmoyer References: <1560366952-10660-1-git-send-email-cai@lca.pw> <1560376072.5154.6.camel@lca.pw> <87lfy4ilvj.fsf@linux.ibm.com> <20190614153535.GA9900@linux> From: "Aneesh Kumar K.V" Date: Fri, 14 Jun 2019 21:56:00 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 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-TM-AS-GCONF: 00 x-cbid: 19061416-0016-0000-0000-000009C27AEC X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011261; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000286; SDB=6.01217915; UDB=6.00640491; IPR=6.00999036; MB=3.00027312; MTD=3.00000008; XFM=3.00000015; UTC=2019-06-14 16:26:06 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19061416-0017-0000-0000-000043A6B53A Message-Id: <24fcb721-5d50-2c34-f44b-69281c8dd760@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-14_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=27 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906140134 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 6/14/19 9:52 PM, Dan Williams wrote: > On Fri, Jun 14, 2019 at 9:18 AM Aneesh Kumar K.V > wrote: >> >> On 6/14/19 9:05 PM, Oscar Salvador wrote: >>> On Fri, Jun 14, 2019 at 02:28:40PM +0530, Aneesh Kumar K.V wrote: >>>> Can you check with this change on ppc64. I haven't reviewed this series yet. >>>> I did limited testing with change . Before merging this I need to go >>>> through the full series again. The vmemmap poplulate on ppc64 needs to >>>> handle two translation mode (hash and radix). With respect to vmemap >>>> hash doesn't setup a translation in the linux page table. Hence we need >>>> to make sure we don't try to setup a mapping for a range which is >>>> arleady convered by an existing mapping. >>>> >>>> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c >>>> index a4e17a979e45..15c342f0a543 100644 >>>> --- a/arch/powerpc/mm/init_64.c >>>> +++ b/arch/powerpc/mm/init_64.c >>>> @@ -88,16 +88,23 @@ static unsigned long __meminit vmemmap_section_start(unsigned long page) >>>> * which overlaps this vmemmap page is initialised then this page is >>>> * initialised already. >>>> */ >>>> -static int __meminit vmemmap_populated(unsigned long start, int page_size) >>>> +static bool __meminit vmemmap_populated(unsigned long start, int page_size) >>>> { >>>> unsigned long end = start + page_size; >>>> start = (unsigned long)(pfn_to_page(vmemmap_section_start(start))); >>>> >>>> - for (; start < end; start += (PAGES_PER_SECTION * sizeof(struct page))) >>>> - if (pfn_valid(page_to_pfn((struct page *)start))) >>>> - return 1; >>>> + for (; start < end; start += (PAGES_PER_SECTION * sizeof(struct page))) { >>>> >>>> - return 0; >>>> + struct mem_section *ms; >>>> + unsigned long pfn = page_to_pfn((struct page *)start); >>>> + >>>> + if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS) >>>> + return 0; >>> >>> I might be missing something, but is this right? >>> Having a section_nr above NR_MEM_SECTIONS is invalid, but if we return 0 here, >>> vmemmap_populate will go on and populate it. >> >> I should drop that completely. We should not hit that condition at all. >> I will send a final patch once I go through the full patch series making >> sure we are not breaking any ppc64 details. >> >> Wondering why we did the below >> >> #if defined(ARCH_SUBSECTION_SHIFT) >> #define SUBSECTION_SHIFT (ARCH_SUBSECTION_SHIFT) >> #elif defined(PMD_SHIFT) >> #define SUBSECTION_SHIFT (PMD_SHIFT) >> #else >> /* >> * Memory hotplug enabled platforms avoid this default because they >> * either define ARCH_SUBSECTION_SHIFT, or PMD_SHIFT is a constant, but >> * this is kept as a backstop to allow compilation on >> * !ARCH_ENABLE_MEMORY_HOTPLUG archs. >> */ >> #define SUBSECTION_SHIFT 21 >> #endif >> >> why not >> >> #if defined(ARCH_SUBSECTION_SHIFT) >> #define SUBSECTION_SHIFT (ARCH_SUBSECTION_SHIFT) >> #else >> #define SUBSECTION_SHIFT SECTION_SHIFT That should be SECTION_SIZE_SHIFT >> #endif >> >> ie, if SUBSECTION is not supported by arch we have one sub-section per >> section? > > A couple comments: > > The only reason ARCH_SUBSECTION_SHIFT exists is because PMD_SHIFT on > PowerPC was a non-constant value. However, I'm planning to remove the > distinction in the next rev of the patches. Jeff rightly points out > that having a variable subsection size per arch will lead to > situations where persistent memory namespaces are not portable across > archs. So I plan to just make SUBSECTION_SHIFT 21 everywhere. > persistent memory namespaces are not portable across archs because they have PAGE_SIZE dependency. Then we have dependencies like the page size with which we map the vmemmap area. Why not let the arch arch decide the SUBSECTION_SHIFT and default to one subsection per section if arch is not enabled to work with subsection. -aneesh