@altmap is stored in a dev_pagemap, but it will be repurposed for
hotplug memory for storing the memmap in the hotplugged memory[*] and
reusing the altmap infrastructure to that end. This is to say that
altmap can't be replaced with a @pgmap as it is going to cover more than
dev_pagemap backend altmaps.

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 align
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.

[*] https://lore.kernel.org/linux-mm/20210319092635.6214-1-osalva...@suse.de/

Signed-off-by: Joao Martins <joao.m.mart...@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 a85d4b7d15c2..45532192934c 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);
@@ -72,6 +73,7 @@ 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);
@@ -360,7 +362,8 @@ 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 cb1e191da319..61474602c2b1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3033,7 +3033,8 @@ static inline void print_vma_addr(char *prefix, unsigned 
long rip)
 
 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 e0b499a1fee4..2df3b2a7b4b5 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -384,7 +384,8 @@ 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 16183d85a7d5..370728c206ee 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -249,7 +249,8 @@ 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 be66a62e22c3..c2abf1281a89 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -443,7 +443,8 @@ 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);
@@ -542,7 +543,7 @@ 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);
@@ -648,9 +649,10 @@ 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,
@@ -719,7 +721,8 @@ 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);
@@ -842,7 +845,8 @@ 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;
@@ -874,7 +878,7 @@ 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);
@@ -889,6 +893,7 @@ 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
  *
  * This is only intended for hotplug.
  *
@@ -902,7 +907,8 @@ 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;
@@ -913,7 +919,7 @@ 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
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