linux-kernel - Re: [PATCH v2 5/8] mm/memory_hotplug: Drop MHP_MEMBLOCK

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Date:   Wed, 8 May 2019 09:39:10 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-ia64@...r.kernel.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Linux-sh <linux-sh@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Oscar Salvador <osalvador@...e.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, Qian Cai <cai@....pw>,
        Arun KS <arunks@...eaurora.org>,
        Mathieu Malaterre <malat@...ian.org>
Subject: Re: [PATCH v2 5/8] mm/memory_hotplug: Drop MHP_MEMBLOCK_API

On 07.05.19 23:25, Dan Williams wrote:
> On Tue, May 7, 2019 at 2:24 PM David Hildenbrand <david@...hat.com> wrote:
>>
>> On 07.05.19 23:19, Dan Williams wrote:
>>> On Tue, May 7, 2019 at 11:38 AM David Hildenbrand <david@...hat.com> wrote:
>>>>
>>>> No longer needed, the callers of arch_add_memory() can handle this
>>>> manually.
>>>>
>>>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>>>> Cc: David Hildenbrand <david@...hat.com>
>>>> Cc: Michal Hocko <mhocko@...e.com>
>>>> Cc: Oscar Salvador <osalvador@...e.com>
>>>> Cc: Pavel Tatashin <pasha.tatashin@...een.com>
>>>> Cc: Wei Yang <richard.weiyang@...il.com>
>>>> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
>>>> Cc: Qian Cai <cai@....pw>
>>>> Cc: Arun KS <arunks@...eaurora.org>
>>>> Cc: Mathieu Malaterre <malat@...ian.org>
>>>> Signed-off-by: David Hildenbrand <david@...hat.com>
>>>> ---
>>>>  include/linux/memory_hotplug.h | 8 --------
>>>>  mm/memory_hotplug.c            | 9 +++------
>>>>  2 files changed, 3 insertions(+), 14 deletions(-)
>>>>
>>>> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
>>>> index 2d4de313926d..2f1f87e13baa 100644
>>>> --- a/include/linux/memory_hotplug.h
>>>> +++ b/include/linux/memory_hotplug.h
>>>> @@ -128,14 +128,6 @@ extern void arch_remove_memory(int nid, u64 start, u64 size,
>>>>  extern void __remove_pages(struct zone *zone, unsigned long start_pfn,
>>>>                            unsigned long nr_pages, struct vmem_altmap *altmap);
>>>>
>>>> -/*
>>>> - * Do we want sysfs memblock files created. This will allow userspace to online
>>>> - * and offline memory explicitly. Lack of this bit means that the caller has to
>>>> - * call move_pfn_range_to_zone to finish the initialization.
>>>> - */
>>>> -
>>>> -#define MHP_MEMBLOCK_API               (1<<0)
>>>> -
>>>>  /* reasonably generic interface to expand the physical pages */
>>>>  extern int __add_pages(int nid, unsigned long start_pfn, unsigned long nr_pages,
>>>>                        struct mhp_restrictions *restrictions);
>>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>>>> index e1637c8a0723..107f72952347 100644
>>>> --- a/mm/memory_hotplug.c
>>>> +++ b/mm/memory_hotplug.c
>>>> @@ -250,7 +250,7 @@ void __init register_page_bootmem_info_node(struct pglist_data *pgdat)
>>>>  #endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */
>>>>
>>>>  static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
>>>> -               struct vmem_altmap *altmap, bool want_memblock)
>>>> +                                  struct vmem_altmap *altmap)
>>>>  {
>>>>         int ret;
>>>>
>>>> @@ -293,8 +293,7 @@ int __ref __add_pages(int nid, unsigned long phys_start_pfn,
>>>>         }
>>>>
>>>>         for (i = start_sec; i <= end_sec; i++) {
>>>> -               err = __add_section(nid, section_nr_to_pfn(i), altmap,
>>>> -                               restrictions->flags & MHP_MEMBLOCK_API);
>>>> +               err = __add_section(nid, section_nr_to_pfn(i), altmap);
>>>>
>>>>                 /*
>>>>                  * EEXIST is finally dealt with by ioresource collision
>>>> @@ -1066,9 +1065,7 @@ static int online_memory_block(struct memory_block *mem, void *arg)
>>>>   */
>>>>  int __ref add_memory_resource(int nid, struct resource *res)
>>>>  {
>>>> -       struct mhp_restrictions restrictions = {
>>>> -               .flags = MHP_MEMBLOCK_API,
>>>> -       };
>>>> +       struct mhp_restrictions restrictions = {};
>>>
>>> With mhp_restrictions.flags no longer needed, can we drop
>>> mhp_restrictions and just go back to a plain @altmap argument?
>>>
>>
>> Oscar wants to use it to configure from where to allocate vmemmaps. That
>> was the original driver behind it.
>>
> 
> Ah, ok, makes sense.
> 

However I haven't really thought it through yet, smalles like that could
as well just be handled by the caller of
arch_add_memory()/arch_remove_memory() eventually, passing it via
something like the altmap parameter.

Let's leave it in place for now, we can talk about that once we have new
patches from Oscar.

-- 

Thanks,

David / dhildenb