Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: Qian Cai <cai@lca.pw>, Dan Williams <dan.j.williams@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux MM <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH -next] mm/hotplug: skip bad PFNs from pfn_to_online_page()
Date: Fri, 14 Jun 2019 21:48:13 +0530
Message-ID: <c3f2c05d-e42f-c942-1385-664f646ddd33@linux.ibm.com> (raw)
In-Reply-To: <20190614153535.GA9900@linux>

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
#endif

ie, if SUBSECTION is not supported by arch we have one sub-section per 
section?


-aneesh


  reply index

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-12 19:15 Qian Cai
2019-06-12 19:37 ` Dan Williams
2019-06-12 19:38   ` Dan Williams
2019-06-12 21:47     ` Qian Cai
2019-06-12 21:52       ` Dan Williams
2019-06-12 23:13         ` Dan Williams
2019-06-13  0:06       ` Dan Williams
2019-06-14  8:58       ` Aneesh Kumar K.V
2019-06-14 14:59         ` Qian Cai
2019-06-14 18:03           ` Dan Williams
2019-06-14 18:57             ` Dan Williams
2019-06-14 19:40               ` Qian Cai
2019-06-14 19:48                 ` Dan Williams
2019-06-14 20:43                   ` Qian Cai
2019-06-16 15:42                     ` Dan Williams
2019-06-17  2:25                       ` Qian Cai
2019-06-14 15:35         ` Oscar Salvador
2019-06-14 16:18           ` Aneesh Kumar K.V [this message]
2019-06-14 16:22             ` Dan Williams
2019-06-14 16:26               ` Aneesh Kumar K.V
2019-06-14 16:36                 ` Dan Williams
2019-06-14 16:50                   ` Aneesh Kumar K.V
2019-06-14 16:55                   ` Aneesh Kumar K.V
2019-06-14 17:08                     ` Jeff Moyer
2019-06-14 17:14                       ` Dan Williams
2019-06-14 17:40                       ` Aneesh Kumar K.V
2019-06-16  3:49               ` Aneesh Kumar K.V
2019-06-17 17:21                 ` Dan Williams
2019-06-13 18:42   ` Qian Cai
2019-06-14  1:17     ` Dan Williams
2019-06-14  1:29       ` Qian Cai

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=c3f2c05d-e42f-c942-1385-664f646ddd33@linux.ibm.com \
    --to=aneesh.kumar@linux.ibm.com \
    --cc=akpm@linux-foundation.org \
    --cc=cai@lca.pw \
    --cc=dan.j.williams@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=osalvador@suse.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org linux-mm@archiver.kernel.org
	public-inbox-index linux-mm


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/ public-inbox