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Re: [PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device_section

From Jerome Glisse <jglisse@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device_section
Date 2017-04-10 18:30 +0200
Message-ID <tuKmu-341-7@gated-at.bofh.it> (permalink)
References <tuFmO-8iD-7@gated-at.bofh.it> <tuFmP-8iD-29@gated-at.bofh.it>
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On Mon, Apr 10, 2017 at 01:03:46PM +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
> 
> device memory hotplug hooks into regular memory hotplug only half way.
> It needs memory sections to track struct pages but there is no
> need/desire to associate those sections with memory blocks and export
> them to the userspace via sysfs because they cannot be onlined anyway.
> 
> This is currently expressed by for_device argument to arch_add_memory
> which then makes sure to associate the given memory range with
> ZONE_DEVICE. register_new_memory then relies on is_zone_device_section
> to distinguish special memory hotplug from the regular one. While this
> works now, later patches in this series want to move __add_zone outside
> of arch_add_memory path so we have to come up with something else.
> 
> Add want_memblock down the __add_pages path and use it to control
> whether the section->memblock association should be done. arch_add_memory
> then just trivially want memblock for everything but for_device hotplug.
> 
> remove_memory_section doesn't need is_zone_device_section either. We can
> simply skip all the memblock specific cleanup if there is no memblock
> for the given section.
> 
> This shouldn't introduce any functional change.
> 
> Cc: Dan Williams <dan.j.williams@gmail.com>
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---

[...]

> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 342332f29364..1570b3eea493 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -493,7 +493,7 @@ static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
>  }
>  
>  static int __meminit __add_section(int nid, struct zone *zone,
> -					unsigned long phys_start_pfn)
> +					unsigned long phys_start_pfn, bool want_memblock)
>  {
>  	int ret;
>  
> @@ -510,7 +510,10 @@ static int __meminit __add_section(int nid, struct zone *zone,
>  	if (ret < 0)
>  		return ret;
>  
> -	return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
> +	if (want_memblock)
> +		ret = register_new_memory(nid, __pfn_to_section(phys_start_pfn));
> +
> +	return ret;
>  }

The above is wrong for ZONE_DEVICE sparse_add_one_section() will return a
positive value (on success) thus ret > 0 and other function in the hotplug
path will interpret positive value as an error.

I suggest something like:
	if (!want_memblock)
		return 0;

	return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
}

instead (also avoid a > 80 columns warning message).

Cheers,
Jérôme

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Thread

[PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-10 13:10 +0200
  [PATCH 3/9] mm: drop page_initialized check from get_nid_for_pfn Michal Hocko <mhocko@kernel.org> - 2017-04-10 13:10 +0200
    Re: [PATCH 3/9] mm: drop page_initialized check from get_nid_for_pfn Vlastimil Babka <vbabka@suse.cz> - 2017-04-13 15:00 +0200
  [PATCH 9/9] mm, memory_hotplug: remove unused cruft after memory hotplug rework Michal Hocko <mhocko@kernel.org> - 2017-04-10 13:10 +0200
    Re: [PATCH 9/9] mm, memory_hotplug: remove unused cruft after memory  hotplug rework Vlastimil Babka <vbabka@suse.cz> - 2017-04-20 10:40 +0200
  [PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device_section Michal Hocko <mhocko@kernel.org> - 2017-04-10 13:10 +0200
    Re: [PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device_section Jerome Glisse <jglisse@redhat.com> - 2017-04-10 18:30 +0200
      Re: [PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device_section Michal Hocko <mhocko@kernel.org> - 2017-04-10 18:40 +0200
    Re: [PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device_section Vlastimil Babka <vbabka@suse.cz> - 2017-04-13 15:10 +0200
    Re: [PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device_section Jerome Glisse <jglisse@redhat.com> - 2017-04-17 22:20 +0200
      Re: [PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device_section Michal Hocko <mhocko@kernel.org> - 2017-04-18 09:20 +0200
  [PATCH 5/9] mm, memory_hotplug: split up register_one_node Michal Hocko <mhocko@kernel.org> - 2017-04-10 13:10 +0200
    Re: [PATCH 5/9] mm, memory_hotplug: split up register_one_node Vlastimil Babka <vbabka@suse.cz> - 2017-04-13 16:10 +0200
      Re: [PATCH 5/9] mm, memory_hotplug: split up register_one_node Michal Hocko <mhocko@kernel.org> - 2017-04-13 16:20 +0200
  Re: [PATCH -v2 0/9] mm: make movable onlining suck less Igor Mammedov <imammedo@redhat.com> - 2017-04-10 16:30 +0200
    Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-10 17:00 +0200
      Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-10 17:30 +0200
        Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-10 17:40 +0200
      Re: [PATCH -v2 0/9] mm: make movable onlining suck less Igor Mammedov <imammedo@redhat.com> - 2017-04-11 10:10 +0200
        Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-11 10:50 +0200
          Re: [PATCH -v2 0/9] mm: make movable onlining suck less Igor Mammedov <imammedo@redhat.com> - 2017-04-11 12:00 +0200
            Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-11 12:50 +0200
    Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-10 18:10 +0200
      Re: [PATCH -v2 0/9] mm: make movable onlining suck less Vlastimil Babka <vbabka@suse.cz> - 2017-04-18 10:30 +0200
    Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-10 18:10 +0200
      Re: [PATCH -v2 0/9] mm: make movable onlining suck less Igor Mammedov <imammedo@redhat.com> - 2017-04-11 08:40 +0200
        Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-11 11:30 +0200
          Re: [PATCH -v2 0/9] mm: make movable onlining suck less Igor Mammedov <imammedo@redhat.com> - 2017-04-11 12:00 +0200
            Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-11 13:10 +0200
              Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-11 13:40 +0200
                Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-11 14:40 +0200
  Re: [PATCH -v2 0/9] mm: make movable onlining suck less Reza Arbab <arbab@linux.vnet.ibm.com> - 2017-04-10 17:50 +0200
    Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-11 11:00 +0200
  Re: [PATCH -v2 0/9] mm: make movable onlining suck less Jerome Glisse <jglisse@redhat.com> - 2017-04-10 18:40 +0200
    Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-10 20:00 +0200
    Re: [PATCH -v2 0/9] mm: make movable onlining suck less Balbir Singh <bsingharora@gmail.com> - 2017-04-11 05:00 +0200
  Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-11 19:10 +0200
    Re: [PATCH -v2 0/9] mm: make movable onlining suck less Dan Williams <dan.j.williams@gmail.com> - 2017-04-18 00:00 +0200
      Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-18 09:20 +0200
        Re: [PATCH -v2 0/9] mm: make movable onlining suck less Dan Williams <dan.j.williams@gmail.com> - 2017-04-18 18:50 +0200
          Re: [PATCH -v2 0/9] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-04-18 22:00 +0200
            Re: [PATCH -v2 0/9] mm: make movable onlining suck less Dan Williams <dan.j.williams@intel.com> - 2017-04-20 05:40 +0200
  [PATCH 3/3] mm: __first_valid_page skip over offline pages Michal Hocko <mhocko@kernel.org> - 2017-04-15 14:20 +0200
  [PATCH 1/3] mm: consider zone which is not fully populated to have holes Michal Hocko <mhocko@kernel.org> - 2017-04-15 14:20 +0200
    Re: [PATCH 1/3] mm: consider zone which is not fully populated to  have holes Vlastimil Babka <vbabka@suse.cz> - 2017-04-18 10:50 +0200
      Re: [PATCH 1/3] mm: consider zone which is not fully populated to  have holes Michal Hocko <mhocko@kernel.org> - 2017-04-18 11:30 +0200
        Re: [PATCH 1/3] mm: consider zone which is not fully populated to  have holes Vlastimil Babka <vbabka@suse.cz> - 2017-04-19 14:00 +0200
          Re: [PATCH 1/3] mm: consider zone which is not fully populated to  have holes Michal Hocko <mhocko@kernel.org> - 2017-04-19 14:20 +0200
            Re: [PATCH 1/3] mm: consider zone which is not fully populated to  have holes Vlastimil Babka <vbabka@suse.cz> - 2017-04-19 14:40 +0200
              Re: [PATCH 1/3] mm: consider zone which is not fully populated to  have holes Michal Hocko <mhocko@kernel.org> - 2017-04-19 15:00 +0200
  (none) Michal Hocko <mhocko@kernel.org> - 2017-04-15 14:20 +0200
    [PATCH 2/3] mm, compaction: skip over holes in __reset_isolation_suitable Michal Hocko <mhocko@kernel.org> - 2017-04-15 14:20 +0200
    Re: your mail Joonsoo Kim <js1304@gmail.com> - 2017-04-17 07:50 +0200
      Re: your mail Michal Hocko <mhocko@kernel.org> - 2017-04-17 10:20 +0200
        Re: your mail Joonsoo Kim <js1304@gmail.com> - 2017-04-20 03:30 +0200
          Re: your mail Michal Hocko <mhocko@kernel.org> - 2017-04-20 09:30 +0200
            Re: your mail Michal Hocko <mhocko@kernel.org> - 2017-04-20 10:50 +0200
              Re: your mail Vlastimil Babka <vbabka@suse.cz> - 2017-04-20 14:00 +0200
                Re: your mail Michal Hocko <mhocko@kernel.org> - 2017-04-20 14:20 +0200
            Re: your mail Joonsoo Kim <js1304@gmail.com> - 2017-04-21 06:40 +0200
              Re: your mail Michal Hocko <mhocko@kernel.org> - 2017-04-21 09:20 +0200
                Re: your mail Joonsoo Kim <js1304@gmail.com> - 2017-04-24 03:50 +0200
                Re: your mail Michal Hocko <mhocko@kernel.org> - 2017-04-24 10:00 +0200

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