mm/sparse-vmemmap.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Virtual Memory Map support
  *
  * (C) 2007 sgi. Christoph Lameter.
  *
  * Virtual memory maps allow VM primitives pfn_to_page, page_to_pfn,
  * virt_to_page, page_address() to be implemented as a base offset
  * calculation without memory access.
  *
  * However, virtual mappings need a page table and TLBs. Many Linux
  * architectures already map their physical space using 1-1 mappings
  * via TLBs. For those arches the virtual memory map is essentially
  * for free if we use the same page size as the 1-1 mappings. In that
  * case the overhead consists of a few additional pages that are
  * allocated to create a view of memory for vmemmap.
  *
  * The architecture is expected to provide a vmemmap_populate() function
  * to instantiate the mapping.
  */
 #include <linux/mm.h>
 #include <linux/mmzone.h>
 #include <linux/memblock.h>
 #include <linux/memremap.h>
 #include <linux/highmem.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/vmalloc.h>
 #include <linux/sched.h>

 #include <asm/dma.h>
 #include <asm/pgalloc.h>

 /*
  * Allocate a block of memory to be used to back the virtual memory map
  * or to back the page tables that are used to create the mapping.
  * Uses the main allocators if they are available, else bootmem.
  */

 static void * __ref __earlyonly_bootmem_alloc(int node,
 				unsigned long size,
 				unsigned long align,
 				unsigned long goal)
 {
 	return memblock_alloc_try_nid_raw(size, align, goal,
 					       MEMBLOCK_ALLOC_ACCESSIBLE, node);
 }

 void * __meminit vmemmap_alloc_block(unsigned long size, int node)
 {
 	/* If the main allocator is up use that, fallback to bootmem. */
 	if (slab_is_available()) {
 		gfp_t gfp_mask = GFP_KERNEL|__GFP_RETRY_MAYFAIL|__GFP_NOWARN;
 		int order = get_order(size);
 		static bool warned;
 		struct page *page;

 		page = alloc_pages_node(node, gfp_mask, order);
 		if (page)
 			return page_address(page);

 		if (!warned) {
 			warn_alloc(gfp_mask & ~__GFP_NOWARN, NULL,
 				   "vmemmap alloc failure: order:%u", order);
 			warned = true;
 		}
 		return NULL;
 	} else
 		return __earlyonly_bootmem_alloc(node, size, size,
 				__pa(MAX_DMA_ADDRESS));
 }

 static void * __meminit altmap_alloc_block_buf(unsigned long size,
 					       struct vmem_altmap *altmap);

 /* need to make sure size is all the same during early stage */
 void * __meminit vmemmap_alloc_block_buf(unsigned long size, int node,
 					 struct vmem_altmap *altmap)
 {
 	void *ptr;

 	if (altmap)
 		return altmap_alloc_block_buf(size, altmap);

 	ptr = sparse_buffer_alloc(size);
 	if (!ptr)
 		ptr = vmemmap_alloc_block(size, node);
 	return ptr;
 }

 static unsigned long __meminit vmem_altmap_next_pfn(struct vmem_altmap *altmap)
 {
 	return altmap->base_pfn + altmap->reserve + altmap->alloc
 		+ altmap->align;
 }

 static unsigned long __meminit vmem_altmap_nr_free(struct vmem_altmap *altmap)
 {
 	unsigned long allocated = altmap->alloc + altmap->align;

 	if (altmap->free > allocated)
 		return altmap->free - allocated;
 	return 0;
 }

 static void * __meminit altmap_alloc_block_buf(unsigned long size,
 					       struct vmem_altmap *altmap)
 {
 	unsigned long pfn, nr_pfns, nr_align;

 	if (size & ~PAGE_MASK) {
 		pr_warn_once("%s: allocations must be multiple of PAGE_SIZE (%ld)\n",
 				__func__, size);
 		return NULL;
 	}

 	pfn = vmem_altmap_next_pfn(altmap);
 	nr_pfns = size >> PAGE_SHIFT;
 	nr_align = 1UL << find_first_bit(&nr_pfns, BITS_PER_LONG);
 	nr_align = ALIGN(pfn, nr_align) - pfn;
 	if (nr_pfns + nr_align > vmem_altmap_nr_free(altmap))
 		return NULL;

 	altmap->alloc += nr_pfns;
 	altmap->align += nr_align;
 	pfn += nr_align;

 	pr_debug("%s: pfn: %#lx alloc: %ld align: %ld nr: %#lx\n",
 			__func__, pfn, altmap->alloc, altmap->align, nr_pfns);
 	return __va(__pfn_to_phys(pfn));
 }

 void __meminit vmemmap_verify(pte_t *pte, int node,
 				unsigned long start, unsigned long end)
 {
 	unsigned long pfn = pte_pfn(ptep_get(pte));
 	int actual_node = early_pfn_to_nid(pfn);

 	if (node_distance(actual_node, node) > LOCAL_DISTANCE)
 		pr_warn_once("[%lx-%lx] potential offnode page_structs\n",
 			start, end - 1);
 }

 pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
 				       struct vmem_altmap *altmap,
 				       struct page *reuse)
 {
 	pte_t *pte = pte_offset_kernel(pmd, addr);
 	if (pte_none(ptep_get(pte))) {
 		pte_t entry;
 		void *p;

 		if (!reuse) {
 			p = vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap);
 			if (!p)
 				return NULL;
 		} else {
 			/*
 			 * When a PTE/PMD entry is freed from the init_mm
 			 * there's a free_pages() call to this page allocated
 			 * above. Thus this get_page() is paired with the
 			 * put_page_testzero() on the freeing path.
 			 * This can only called by certain ZONE_DEVICE path,
 			 * and through vmemmap_populate_compound_pages() when
 			 * slab is available.
 			 */
 			get_page(reuse);
 			p = page_to_virt(reuse);
 		}
 		entry = pfn_pte(__pa(p) >> PAGE_SHIFT, PAGE_KERNEL);
 		set_pte_at(&init_mm, addr, pte, entry);
 	}
 	return pte;
 }

 static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node)
 {
 	void *p = vmemmap_alloc_block(size, node);

 	if (!p)
 		return NULL;
 	memset(p, 0, size);

 	return p;
 }

 pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)
 {
 	pmd_t *pmd = pmd_offset(pud, addr);
 	if (pmd_none(*pmd)) {
 		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 		if (!p)
 			return NULL;
 		pmd_populate_kernel(&init_mm, pmd, p);
 	}
 	return pmd;
 }

 void __weak __meminit pmd_init(void *addr)
 {
 }

 pud_t * __meminit vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node)
 {
 	pud_t *pud = pud_offset(p4d, addr);
 	if (pud_none(*pud)) {
 		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 		if (!p)
 			return NULL;
 		pmd_init(p);
 		pud_populate(&init_mm, pud, p);
 	}
 	return pud;
 }

 void __weak __meminit pud_init(void *addr)
 {
 }

 p4d_t * __meminit vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node)
 {
 	p4d_t *p4d = p4d_offset(pgd, addr);
 	if (p4d_none(*p4d)) {
 		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 		if (!p)
 			return NULL;
 		pud_init(p);
 		p4d_populate(&init_mm, p4d, p);
 	}
 	return p4d;
 }

 pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node)
 {
 	pgd_t *pgd = pgd_offset_k(addr);
 	if (pgd_none(*pgd)) {
 		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 		if (!p)
 			return NULL;
 		pgd_populate(&init_mm, pgd, p);
 	}
 	return pgd;
 }

 static pte_t * __meminit vmemmap_populate_address(unsigned long addr, int node,
 					      struct vmem_altmap *altmap,
 					      struct page *reuse)
 {
 	pgd_t *pgd;
 	p4d_t *p4d;
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;

 	pgd = vmemmap_pgd_populate(addr, node);
 	if (!pgd)
 		return NULL;
 	p4d = vmemmap_p4d_populate(pgd, addr, node);
 	if (!p4d)
 		return NULL;
 	pud = vmemmap_pud_populate(p4d, addr, node);
 	if (!pud)
 		return NULL;
 	pmd = vmemmap_pmd_populate(pud, addr, node);
 	if (!pmd)
 		return NULL;
 	pte = vmemmap_pte_populate(pmd, addr, node, altmap, reuse);
 	if (!pte)
 		return NULL;
 	vmemmap_verify(pte, node, addr, addr + PAGE_SIZE);

 	return pte;
 }

 static int __meminit vmemmap_populate_range(unsigned long start,
 					    unsigned long end, int node,
 					    struct vmem_altmap *altmap,
 					    struct page *reuse)
 {
 	unsigned long addr = start;
 	pte_t *pte;

 	for (; addr < end; addr += PAGE_SIZE) {
 		pte = vmemmap_populate_address(addr, node, altmap, reuse);
 		if (!pte)
 			return -ENOMEM;
 	}

 	return 0;
 }

 int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
 					 int node, struct vmem_altmap *altmap)
 {
 	return vmemmap_populate_range(start, end, node, altmap, NULL);
 }

 void __weak __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
 				      unsigned long addr, unsigned long next)
 {
 }

 int __weak __meminit vmemmap_check_pmd(pmd_t *pmd, int node,
 				       unsigned long addr, unsigned long next)
 {
 	return 0;
 }

 int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end,
 					 int node, struct vmem_altmap *altmap)
 {
 	unsigned long addr;
 	unsigned long next;
 	pgd_t *pgd;
 	p4d_t *p4d;
 	pud_t *pud;
 	pmd_t *pmd;

 	for (addr = start; addr < end; addr = next) {
 		next = pmd_addr_end(addr, end);

 		pgd = vmemmap_pgd_populate(addr, node);
 		if (!pgd)
 			return -ENOMEM;

 		p4d = vmemmap_p4d_populate(pgd, addr, node);
 		if (!p4d)
 			return -ENOMEM;

 		pud = vmemmap_pud_populate(p4d, addr, node);
 		if (!pud)
 			return -ENOMEM;

 		pmd = pmd_offset(pud, addr);
 		if (pmd_none(READ_ONCE(*pmd))) {
 			void *p;

 			p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap);
 			if (p) {
 				vmemmap_set_pmd(pmd, p, node, addr, next);
 				continue;
 			} else if (altmap) {
 				/*
 				 * No fallback: In any case we care about, the
 				 * altmap should be reasonably sized and aligned
 				 * such that vmemmap_alloc_block_buf() will always
 				 * succeed. For consistency with the PTE case,
 				 * return an error here as failure could indicate
 				 * a configuration issue with the size of the altmap.
 				 */
 				return -ENOMEM;
 			}
 		} else if (vmemmap_check_pmd(pmd, node, addr, next))
 			continue;
 		if (vmemmap_populate_basepages(addr, next, node, altmap))
 			return -ENOMEM;
 	}
 	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 pte_t * __meminit compound_section_tail_page(unsigned long addr)
 {
 	pte_t *pte;

 	addr -= PAGE_SIZE;

 	/*
 	 * Assuming sections are populated sequentially, the previous section's
 	 * page data can be reused.
 	 */
 	pte = pte_offset_kernel(pmd_off_k(addr), addr);
 	if (!pte)
 		return NULL;

 	return pte;
 }

 static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn,
 						     unsigned long start,
 						     unsigned long end, int node,
 						     struct dev_pagemap *pgmap)
 {
 	unsigned long size, addr;
 	pte_t *pte;
 	int rc;

 	if (reuse_compound_section(start_pfn, pgmap)) {
 		pte = compound_section_tail_page(start);
 		if (!pte)
 			return -ENOMEM;

 		/*
 		 * Reuse the page that was populated in the prior iteration
 		 * with just tail struct pages.
 		 */
 		return vmemmap_populate_range(start, end, node, NULL,
 					      pte_page(ptep_get(pte)));
 	}

 	size = min(end - start, pgmap_vmemmap_nr(pgmap) * 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, NULL);
 		if (!pte)
 			return -ENOMEM;

 		/* Populate the tail pages vmemmap page */
 		next = addr + PAGE_SIZE;
 		pte = vmemmap_populate_address(next, node, NULL, NULL);
 		if (!pte)
 			return -ENOMEM;

 		/*
 		 * Reuse the previous page for the rest of tail pages
 		 * See layout diagram in Documentation/mm/vmemmap_dedup.rst
 		 */
 		next += PAGE_SIZE;
 		rc = vmemmap_populate_range(next, last, node, NULL,
 					    pte_page(ptep_get(pte)));
 		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)
 {
 	unsigned long start = (unsigned long) pfn_to_page(pfn);
 	unsigned long end = start + nr_pages * sizeof(struct page);
 	int r;

 	if (WARN_ON_ONCE(!IS_ALIGNED(pfn, PAGES_PER_SUBSECTION) ||
 		!IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION)))
 		return NULL;

 	if (vmemmap_can_optimize(altmap, pgmap))
 		r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap);
 	else
 		r = vmemmap_populate(start, end, nid, altmap);

 	if (r < 0)
 		return NULL;

 	return pfn_to_page(pfn);
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Virtual Memory Map support
	*
	* (C) 2007 sgi. Christoph Lameter.
	*
	* Virtual memory maps allow VM primitives pfn_to_page, page_to_pfn,
	* virt_to_page, page_address() to be implemented as a base offset
	* calculation without memory access.
	*
	* However, virtual mappings need a page table and TLBs. Many Linux
	* architectures already map their physical space using 1-1 mappings
	* via TLBs. For those arches the virtual memory map is essentially
	* for free if we use the same page size as the 1-1 mappings. In that
	* case the overhead consists of a few additional pages that are
	* allocated to create a view of memory for vmemmap.
	*
	* The architecture is expected to provide a vmemmap_populate() function
	* to instantiate the mapping.
	*/
	#include <linux/mm.h>
	#include <linux/mmzone.h>
	#include <linux/memblock.h>
	#include <linux/memremap.h>
	#include <linux/highmem.h>
	#include <linux/slab.h>
	#include <linux/spinlock.h>
	#include <linux/vmalloc.h>
	#include <linux/sched.h>

	#include <asm/dma.h>
	#include <asm/pgalloc.h>

	/*
	* Allocate a block of memory to be used to back the virtual memory map
	* or to back the page tables that are used to create the mapping.
	* Uses the main allocators if they are available, else bootmem.
	*/

	static void * __ref __earlyonly_bootmem_alloc(int node,
	unsigned long size,
	unsigned long align,
	unsigned long goal)
	{
	return memblock_alloc_try_nid_raw(size, align, goal,
	MEMBLOCK_ALLOC_ACCESSIBLE, node);
	}

	void * __meminit vmemmap_alloc_block(unsigned long size, int node)
	{
	/* If the main allocator is up use that, fallback to bootmem. */
	if (slab_is_available()) {
	gfp_t gfp_mask = GFP_KERNEL\|__GFP_RETRY_MAYFAIL\|__GFP_NOWARN;
	int order = get_order(size);
	static bool warned;
	struct page *page;

	page = alloc_pages_node(node, gfp_mask, order);
	if (page)
	return page_address(page);

	if (!warned) {
	warn_alloc(gfp_mask & ~__GFP_NOWARN, NULL,
	"vmemmap alloc failure: order:%u", order);
	warned = true;
	}
	return NULL;
	} else
	return __earlyonly_bootmem_alloc(node, size, size,
	__pa(MAX_DMA_ADDRESS));
	}

	static void * __meminit altmap_alloc_block_buf(unsigned long size,
	struct vmem_altmap *altmap);

	/* need to make sure size is all the same during early stage */
	void * __meminit vmemmap_alloc_block_buf(unsigned long size, int node,
	struct vmem_altmap *altmap)
	{
	void *ptr;

	if (altmap)
	return altmap_alloc_block_buf(size, altmap);

	ptr = sparse_buffer_alloc(size);
	if (!ptr)
	ptr = vmemmap_alloc_block(size, node);
	return ptr;
	}

	static unsigned long __meminit vmem_altmap_next_pfn(struct vmem_altmap *altmap)
	{
	return altmap->base_pfn + altmap->reserve + altmap->alloc
	+ altmap->align;
	}

	static unsigned long __meminit vmem_altmap_nr_free(struct vmem_altmap *altmap)
	{
	unsigned long allocated = altmap->alloc + altmap->align;

	if (altmap->free > allocated)
	return altmap->free - allocated;
	return 0;
	}

	static void * __meminit altmap_alloc_block_buf(unsigned long size,
	struct vmem_altmap *altmap)
	{
	unsigned long pfn, nr_pfns, nr_align;

	if (size & ~PAGE_MASK) {
	pr_warn_once("%s: allocations must be multiple of PAGE_SIZE (%ld)\n",
	__func__, size);
	return NULL;
	}

	pfn = vmem_altmap_next_pfn(altmap);
	nr_pfns = size >> PAGE_SHIFT;
	nr_align = 1UL << find_first_bit(&nr_pfns, BITS_PER_LONG);
	nr_align = ALIGN(pfn, nr_align) - pfn;
	if (nr_pfns + nr_align > vmem_altmap_nr_free(altmap))
	return NULL;

	altmap->alloc += nr_pfns;
	altmap->align += nr_align;
	pfn += nr_align;

	pr_debug("%s: pfn: %#lx alloc: %ld align: %ld nr: %#lx\n",
	__func__, pfn, altmap->alloc, altmap->align, nr_pfns);
	return __va(__pfn_to_phys(pfn));
	}

	void __meminit vmemmap_verify(pte_t *pte, int node,
	unsigned long start, unsigned long end)
	{
	unsigned long pfn = pte_pfn(ptep_get(pte));
	int actual_node = early_pfn_to_nid(pfn);

	if (node_distance(actual_node, node) > LOCAL_DISTANCE)
	pr_warn_once("[%lx-%lx] potential offnode page_structs\n",
	start, end - 1);
	}

	pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
	struct vmem_altmap *altmap,
	struct page *reuse)
	{
	pte_t *pte = pte_offset_kernel(pmd, addr);
	if (pte_none(ptep_get(pte))) {
	pte_t entry;
	void *p;

	if (!reuse) {
	p = vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap);
	if (!p)
	return NULL;
	} else {
	/*
	* When a PTE/PMD entry is freed from the init_mm
	* there's a free_pages() call to this page allocated
	* above. Thus this get_page() is paired with the
	* put_page_testzero() on the freeing path.
	* This can only called by certain ZONE_DEVICE path,
	* and through vmemmap_populate_compound_pages() when
	* slab is available.
	*/
	get_page(reuse);
	p = page_to_virt(reuse);
	}
	entry = pfn_pte(__pa(p) >> PAGE_SHIFT, PAGE_KERNEL);
	set_pte_at(&init_mm, addr, pte, entry);
	}
	return pte;
	}

	static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node)
	{
	void *p = vmemmap_alloc_block(size, node);

	if (!p)
	return NULL;
	memset(p, 0, size);

	return p;
	}

	pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)
	{
	pmd_t *pmd = pmd_offset(pud, addr);
	if (pmd_none(*pmd)) {
	void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
	if (!p)
	return NULL;
	pmd_populate_kernel(&init_mm, pmd, p);
	}
	return pmd;
	}

	void __weak __meminit pmd_init(void *addr)
	{
	}

	pud_t * __meminit vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node)
	{
	pud_t *pud = pud_offset(p4d, addr);
	if (pud_none(*pud)) {
	void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
	if (!p)
	return NULL;
	pmd_init(p);
	pud_populate(&init_mm, pud, p);
	}
	return pud;
	}

	void __weak __meminit pud_init(void *addr)
	{
	}

	p4d_t * __meminit vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node)
	{
	p4d_t *p4d = p4d_offset(pgd, addr);
	if (p4d_none(*p4d)) {
	void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
	if (!p)
	return NULL;
	pud_init(p);
	p4d_populate(&init_mm, p4d, p);
	}
	return p4d;
	}

	pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node)
	{
	pgd_t *pgd = pgd_offset_k(addr);
	if (pgd_none(*pgd)) {
	void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
	if (!p)
	return NULL;
	pgd_populate(&init_mm, pgd, p);
	}
	return pgd;
	}

	static pte_t * __meminit vmemmap_populate_address(unsigned long addr, int node,
	struct vmem_altmap *altmap,
	struct page *reuse)
	{
	pgd_t *pgd;
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	pgd = vmemmap_pgd_populate(addr, node);
	if (!pgd)
	return NULL;
	p4d = vmemmap_p4d_populate(pgd, addr, node);
	if (!p4d)
	return NULL;
	pud = vmemmap_pud_populate(p4d, addr, node);
	if (!pud)
	return NULL;
	pmd = vmemmap_pmd_populate(pud, addr, node);
	if (!pmd)
	return NULL;
	pte = vmemmap_pte_populate(pmd, addr, node, altmap, reuse);
	if (!pte)
	return NULL;
	vmemmap_verify(pte, node, addr, addr + PAGE_SIZE);

	return pte;
	}

	static int __meminit vmemmap_populate_range(unsigned long start,
	unsigned long end, int node,
	struct vmem_altmap *altmap,
	struct page *reuse)
	{
	unsigned long addr = start;
	pte_t *pte;

	for (; addr < end; addr += PAGE_SIZE) {
	pte = vmemmap_populate_address(addr, node, altmap, reuse);
	if (!pte)
	return -ENOMEM;
	}

	return 0;
	}

	int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
	int node, struct vmem_altmap *altmap)
	{
	return vmemmap_populate_range(start, end, node, altmap, NULL);
	}

	void __weak __meminit vmemmap_set_pmd(pmd_t pmd, void p, int node,
	unsigned long addr, unsigned long next)
	{
	}

	int __weak __meminit vmemmap_check_pmd(pmd_t *pmd, int node,
	unsigned long addr, unsigned long next)
	{
	return 0;
	}

	int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end,
	int node, struct vmem_altmap *altmap)
	{
	unsigned long addr;
	unsigned long next;
	pgd_t *pgd;
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;

	for (addr = start; addr < end; addr = next) {
	next = pmd_addr_end(addr, end);

	pgd = vmemmap_pgd_populate(addr, node);
	if (!pgd)
	return -ENOMEM;

	p4d = vmemmap_p4d_populate(pgd, addr, node);
	if (!p4d)
	return -ENOMEM;

	pud = vmemmap_pud_populate(p4d, addr, node);
	if (!pud)
	return -ENOMEM;

	pmd = pmd_offset(pud, addr);
	if (pmd_none(READ_ONCE(*pmd))) {
	void *p;

	p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap);
	if (p) {
	vmemmap_set_pmd(pmd, p, node, addr, next);
	continue;
	} else if (altmap) {
	/*
	* No fallback: In any case we care about, the
	* altmap should be reasonably sized and aligned
	* such that vmemmap_alloc_block_buf() will always
	* succeed. For consistency with the PTE case,
	* return an error here as failure could indicate
	* a configuration issue with the size of the altmap.
	*/
	return -ENOMEM;
	}
	} else if (vmemmap_check_pmd(pmd, node, addr, next))
	continue;
	if (vmemmap_populate_basepages(addr, next, node, altmap))
	return -ENOMEM;
	}
	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 pte_t * __meminit compound_section_tail_page(unsigned long addr)
	{
	pte_t *pte;

	addr -= PAGE_SIZE;

	/*
	* Assuming sections are populated sequentially, the previous section's
	* page data can be reused.
	*/
	pte = pte_offset_kernel(pmd_off_k(addr), addr);
	if (!pte)
	return NULL;

	return pte;
	}

	static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn,
	unsigned long start,
	unsigned long end, int node,
	struct dev_pagemap *pgmap)
	{
	unsigned long size, addr;
	pte_t *pte;
	int rc;

	if (reuse_compound_section(start_pfn, pgmap)) {
	pte = compound_section_tail_page(start);
	if (!pte)
	return -ENOMEM;

	/*
	* Reuse the page that was populated in the prior iteration
	* with just tail struct pages.
	*/
	return vmemmap_populate_range(start, end, node, NULL,
	pte_page(ptep_get(pte)));
	}

	size = min(end - start, pgmap_vmemmap_nr(pgmap) * 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, NULL);
	if (!pte)
	return -ENOMEM;

	/* Populate the tail pages vmemmap page */
	next = addr + PAGE_SIZE;
	pte = vmemmap_populate_address(next, node, NULL, NULL);
	if (!pte)
	return -ENOMEM;

	/*
	* Reuse the previous page for the rest of tail pages
	* See layout diagram in Documentation/mm/vmemmap_dedup.rst
	*/
	next += PAGE_SIZE;
	rc = vmemmap_populate_range(next, last, node, NULL,
	pte_page(ptep_get(pte)));
	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)
	{
	unsigned long start = (unsigned long) pfn_to_page(pfn);
	unsigned long end = start + nr_pages * sizeof(struct page);
	int r;

	if (WARN_ON_ONCE(!IS_ALIGNED(pfn, PAGES_PER_SUBSECTION) \|\|
	!IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION)))
	return NULL;

	if (vmemmap_can_optimize(altmap, pgmap))
	r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap);
	else
	r = vmemmap_populate(start, end, nid, altmap);

	if (r < 0)
	return NULL;

	return pfn_to_page(pfn);
	}