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mm/sparse-vmemmap: drop Device DAX-specific population path

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The common vmemmap path selects the shared page for optimized mappings
itself, so Device DAX no longer needs vmemmap_populate_compound_pages() to
find a shared tail page and pass its backing PFN through the generic
population helpers.

Remove the Device DAX-specific population path and let section memmap
population always use vmemmap_populate().  The powerpc retains an
architecture-specific compound-page implementation, so select it directly
from radix__vmemmap_populate() for optimizable sections.

Link: https://lore.kernel.org/20261010075755.83339-4-songmuchun@bytedance.com
Signed-off-by: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Acked-by: Qi Zheng <qi.zheng@linux.dev>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <chleroy@kernel.org>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
This commit is contained in:
Muchun Song 2026-10-10 15:57:52 +08:00 committed by Andrew Morton
parent a123cf7ac6
commit bd0862382a
3 changed files with 5 additions and 71 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/powerpc/mm/book3s64/radix_pgtable.c
View File

@ -1126,7 +1126,10 @@ int __meminit radix__vmemmap_populate(unsigned long start, unsigned long end, in
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
unsigned long pfn = page_to_pfn((struct page *)start);
if (vmemmap_optimizable_order(pfn_to_section_compound_order(pfn)))
return vmemmap_populate_compound_pages(pfn, start, end, node, NULL);
/*
* If altmap is present, Make sure we align the start vmemmap addr
* to PAGE_SIZE so that we calculate the correct start_pfn in

2
mm/mm_init.c
View File

@ -1046,7 +1046,7 @@ static void zone_device_page_init_from_template(struct page *page,
* initialize is a lot smaller that the total amount of struct pages being
* mapped. This is a paired / mild layering violation with explicit knowledge
* of how the sparse_vmemmap internals handle compound pages in the lack
* of an altmap. See vmemmap_populate_compound_pages().
* of an altmap.
*/
static inline unsigned long compound_nr_pages(unsigned long pfn,
struct dev_pagemap *pgmap)

71
mm/sparse-vmemmap.c
View File

@ -503,71 +503,6 @@ int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end,
return 0;
}
#ifndef vmemmap_populate_compound_pages
/*
* For compound pages bigger than section size (e.g. x86 1G compound
* pages with 2M subsection size) fill the rest of sections as tail
* pages.
*
* Note that memremap_pages() resets @nr_range value and will increment
* it after each range successful onlining. Thus the value or @nr_range
* at section memmap populate corresponds to the in-progress range
* being onlined here.
*/
static bool __meminit reuse_compound_section(unsigned long start_pfn,
struct dev_pagemap *pgmap)
{
unsigned long nr_pages = pgmap_vmemmap_nr(pgmap);
unsigned long offset = start_pfn -
PHYS_PFN(pgmap->ranges[pgmap->nr_range].start);
return !IS_ALIGNED(offset, nr_pages) && nr_pages > PAGES_PER_SUBSECTION;
}
static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn,
unsigned long start,
unsigned long end, int node,
struct dev_pagemap *pgmap)
{
const unsigned int order = pfn_to_section_compound_order(start_pfn);
unsigned long size, addr;
pte_t *pte;
struct page *page;
int rc;
page = vmemmap_shared_tail_page(order, device_zone(node));
if (!page)
return -ENOMEM;
if (reuse_compound_section(start_pfn, pgmap))
return vmemmap_populate_range(start, end, node, NULL,
page_to_pfn(page));
size = min(end - start, (1UL << order) * sizeof(struct page));
for (addr = start; addr < end; addr += size) {
unsigned long next, last = addr + size;
/* Populate the head page vmemmap page */
pte = vmemmap_populate_address(addr, node, NULL, -1);
if (!pte)
return -ENOMEM;
/*
* Reuse the shared page for the rest of tail pages
* See layout diagram in Documentation/mm/vmemmap_dedup.rst
*/
next = addr + PAGE_SIZE;
rc = vmemmap_populate_range(next, last, node, NULL,
page_to_pfn(page));
if (rc)
return -ENOMEM;
}
return 0;
}
#endif
struct page * __meminit __populate_section_memmap(unsigned long pfn,
unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
struct dev_pagemap *pgmap)
@ -580,11 +515,7 @@ struct page * __meminit __populate_section_memmap(unsigned long pfn,
!IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION)))
return NULL;
if (pgmap && section_vmemmap_optimizable(__pfn_to_section(pfn)))
r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap);
else
r = vmemmap_populate(start, end, nid, altmap);
r = vmemmap_populate(start, end, nid, altmap);
if (r < 0)
return NULL;