Re: [PATCH v3 05/14] mm/sparse-vmemmap: add a pgmap argument to section activation

[Joao Martins <joao.m.martins@oracle.com>]

On 7/28/21 6:56 AM, Dan Williams wrote:
> On Wed, Jul 14, 2021 at 12:36 PM Joao Martins <joao.m.martins@oracle.com> wrote:
>>
>> In support of using compound pages for devmap mappings, plumb the pgmap
>> down to the vmemmap_populate implementation. Note that while altmap is
>> retrievable from pgmap the memory hotplug code passes altmap without
>> pgmap[*], so both need to be independently plumbed.
>>
>> So in addition to @altmap, pass @pgmap to sparse section populate
>> functions namely:
>>
>>         sparse_add_section
>>           section_activate
>>             populate_section_memmap
>>               __populate_section_memmap
>>
>> Passing @pgmap allows __populate_section_memmap() to both fetch the
>> geometry in which memmap metadata is created for and also to let
>> sparse-vmemmap fetch pgmap ranges to co-relate to a given section and pick
>> whether to just reuse tail pages from past onlined sections.
> 
> Looks good to me, just one quibble below:
> 
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> 
Thank you!
>>
>> [*] https://lore.kernel.org/linux-mm/20210319092635.6214-1-osalvador@suse.de/
>>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>>  include/linux/memory_hotplug.h |  5 ++++-
>>  include/linux/mm.h             |  3 ++-
>>  mm/memory_hotplug.c            |  3 ++-
>>  mm/sparse-vmemmap.c            |  3 ++-
>>  mm/sparse.c                    | 24 +++++++++++++++---------
>>  5 files changed, 25 insertions(+), 13 deletions(-)
>>
>> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
>> index a7fd2c3ccb77..9b1bca80224d 100644
>> --- a/include/linux/memory_hotplug.h
>> +++ b/include/linux/memory_hotplug.h
>> @@ -14,6 +14,7 @@ struct mem_section;
>>  struct memory_block;
>>  struct resource;
>>  struct vmem_altmap;
>> +struct dev_pagemap;
>>
>>  #ifdef CONFIG_MEMORY_HOTPLUG
>>  struct page *pfn_to_online_page(unsigned long pfn);
>> @@ -60,6 +61,7 @@ typedef int __bitwise mhp_t;
>>  struct mhp_params {
>>         struct vmem_altmap *altmap;
>>         pgprot_t pgprot;
>> +       struct dev_pagemap *pgmap;
>>  };
>>
>>  bool mhp_range_allowed(u64 start, u64 size, bool need_mapping);
>> @@ -333,7 +335,8 @@ extern void remove_pfn_range_from_zone(struct zone *zone,
>>                                        unsigned long nr_pages);
>>  extern bool is_memblock_offlined(struct memory_block *mem);
>>  extern int sparse_add_section(int nid, unsigned long pfn,
>> -               unsigned long nr_pages, struct vmem_altmap *altmap);
>> +               unsigned long nr_pages, struct vmem_altmap *altmap,
>> +               struct dev_pagemap *pgmap);
>>  extern void sparse_remove_section(struct mem_section *ms,
>>                 unsigned long pfn, unsigned long nr_pages,
>>                 unsigned long map_offset, struct vmem_altmap *altmap);
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 7ca22e6e694a..f244a9219ce4 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -3083,7 +3083,8 @@ int vmemmap_remap_alloc(unsigned long start, unsigned long end,
>>
>>  void *sparse_buffer_alloc(unsigned long size);
>>  struct page * __populate_section_memmap(unsigned long pfn,
>> -               unsigned long nr_pages, int nid, struct vmem_altmap *altmap);
>> +               unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
>> +               struct dev_pagemap *pgmap);
>>  pgd_t *vmemmap_pgd_populate(unsigned long addr, int node);
>>  p4d_t *vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node);
>>  pud_t *vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node);
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 8cb75b26ea4f..c728a8ff38ad 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -268,7 +268,8 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages,
>>                 /* Select all remaining pages up to the next section boundary */
>>                 cur_nr_pages = min(end_pfn - pfn,
>>                                    SECTION_ALIGN_UP(pfn + 1) - pfn);
>> -               err = sparse_add_section(nid, pfn, cur_nr_pages, altmap);
>> +               err = sparse_add_section(nid, pfn, cur_nr_pages, altmap,
>> +                                        params->pgmap);
>>                 if (err)
>>                         break;
>>                 cond_resched();
>> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
>> index bdce883f9286..80d3ba30d345 100644
>> --- a/mm/sparse-vmemmap.c
>> +++ b/mm/sparse-vmemmap.c
>> @@ -603,7 +603,8 @@ int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
>>  }
>>
>>  struct page * __meminit __populate_section_memmap(unsigned long pfn,
>> -               unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
>> +               unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
>> +               struct dev_pagemap *pgmap)
>>  {
>>         unsigned long start = (unsigned long) pfn_to_page(pfn);
>>         unsigned long end = start + nr_pages * sizeof(struct page);
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index 6326cdf36c4f..5310be6171f1 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -453,7 +453,8 @@ static unsigned long __init section_map_size(void)
>>  }
>>
>>  struct page __init *__populate_section_memmap(unsigned long pfn,
>> -               unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
>> +               unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
>> +               struct dev_pagemap *pgmap)
>>  {
>>         unsigned long size = section_map_size();
>>         struct page *map = sparse_buffer_alloc(size);
>> @@ -552,7 +553,7 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin,
>>                         break;
>>
>>                 map = __populate_section_memmap(pfn, PAGES_PER_SECTION,
>> -                               nid, NULL);
>> +                               nid, NULL, NULL);
>>                 if (!map) {
>>                         pr_err("%s: node[%d] memory map backing failed. Some memory will not be available.",
>>                                __func__, nid);
>> @@ -657,9 +658,10 @@ void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn)
>>
>>  #ifdef CONFIG_SPARSEMEM_VMEMMAP
>>  static struct page * __meminit populate_section_memmap(unsigned long pfn,
>> -               unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
>> +               unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
>> +               struct dev_pagemap *pgmap)
>>  {
>> -       return __populate_section_memmap(pfn, nr_pages, nid, altmap);
>> +       return __populate_section_memmap(pfn, nr_pages, nid, altmap, pgmap);
>>  }
>>
>>  static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
>> @@ -728,7 +730,8 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
>>  }
>>  #else
>>  struct page * __meminit populate_section_memmap(unsigned long pfn,
>> -               unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
>> +               unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
>> +               struct dev_pagemap *pgmap)
>>  {
>>         return kvmalloc_node(array_size(sizeof(struct page),
>>                                         PAGES_PER_SECTION), GFP_KERNEL, nid);
>> @@ -851,7 +854,8 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
>>  }
>>
>>  static struct page * __meminit section_activate(int nid, unsigned long pfn,
>> -               unsigned long nr_pages, struct vmem_altmap *altmap)
>> +               unsigned long nr_pages, struct vmem_altmap *altmap,
>> +               struct dev_pagemap *pgmap)
>>  {
>>         struct mem_section *ms = __pfn_to_section(pfn);
>>         struct mem_section_usage *usage = NULL;
>> @@ -883,7 +887,7 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
>>         if (nr_pages < PAGES_PER_SECTION && early_section(ms))
>>                 return pfn_to_page(pfn);
>>
>> -       memmap = populate_section_memmap(pfn, nr_pages, nid, altmap);
>> +       memmap = populate_section_memmap(pfn, nr_pages, nid, altmap, pgmap);
>>         if (!memmap) {
>>                 section_deactivate(pfn, nr_pages, altmap);
>>                 return ERR_PTR(-ENOMEM);
>> @@ -898,6 +902,7 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
>>   * @start_pfn: start pfn of the memory range
>>   * @nr_pages: number of pfns to add in the section
>>   * @altmap: device page map
>> + * @pgmap: device page map object that owns the section
> 
> Since this patch is touching the kdoc, might as well fix it up
> properly for @altmap, and perhaps an alternate note for @pgmap:
> 
> @altmap: alternate pfns to allocate the memmap backing store
> @pgmap: alternate compound page geometry for devmap mappings
> 
Ah, indeed. I fixed it up and also added this to the commit message:

"While at it, fix the kdoc for @altmap for sparse_add_section()."

> 
>>   *
>>   * This is only intended for hotplug.
>>   *
>> @@ -911,7 +916,8 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
>>   * * -ENOMEM   - Out of memory.
>>   */
>>  int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>> -               unsigned long nr_pages, struct vmem_altmap *altmap)
>> +               unsigned long nr_pages, struct vmem_altmap *altmap,
>> +               struct dev_pagemap *pgmap)
>>  {
>>         unsigned long section_nr = pfn_to_section_nr(start_pfn);
>>         struct mem_section *ms;
>> @@ -922,7 +928,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>>         if (ret < 0)
>>                 return ret;
>>
>> -       memmap = section_activate(nid, start_pfn, nr_pages, altmap);
>> +       memmap = section_activate(nid, start_pfn, nr_pages, altmap, pgmap);
>>         if (IS_ERR(memmap))
>>                 return PTR_ERR(memmap);
>>
>> --
>> 2.17.1
>>