[linux-block.git] / mm / sparse-vmemmap.c

// 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(*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(*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;
}

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;
		pud_populate(&init_mm, pud, p);
	}
	return pud;
}

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;
		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);
}

/*
 * 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(*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(*pte));
		if (rc)
			return -ENOMEM;
	}

	return 0;
}

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 (is_power_of_2(sizeof(struct page)) &&
	    pgmap && pgmap_vmemmap_nr(pgmap) > 1 && !altmap)
		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);
}
Commit	Line	Data
	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* Virtual Memory Map support
	4	*
	5	* (C) 2007 sgi. Christoph Lameter.
	6	*
	7	* Virtual memory maps allow VM primitives pfn_to_page, page_to_pfn,
	8	* virt_to_page, page_address() to be implemented as a base offset
	9	* calculation without memory access.
	10	*
	11	* However, virtual mappings need a page table and TLBs. Many Linux
	12	* architectures already map their physical space using 1-1 mappings
	13	* via TLBs. For those arches the virtual memory map is essentially
	14	* for free if we use the same page size as the 1-1 mappings. In that
	15	* case the overhead consists of a few additional pages that are
	16	* allocated to create a view of memory for vmemmap.
	17	*
	18	* The architecture is expected to provide a vmemmap_populate() function
	19	* to instantiate the mapping.
	20	*/
	21	#include <linux/mm.h>
	22	#include <linux/mmzone.h>
	23	#include <linux/memblock.h>
	24	#include <linux/memremap.h>
	25	#include <linux/highmem.h>
	26	#include <linux/slab.h>
	27	#include <linux/spinlock.h>
	28	#include <linux/vmalloc.h>
	29	#include <linux/sched.h>
	30
	31	#include <asm/dma.h>
	32	#include <asm/pgalloc.h>
	33
	34	/*
	35	* Allocate a block of memory to be used to back the virtual memory map
	36	* or to back the page tables that are used to create the mapping.
	37	* Uses the main allocators if they are available, else bootmem.
	38	*/
	39
	40	static void * __ref __earlyonly_bootmem_alloc(int node,
	41	unsigned long size,
	42	unsigned long align,
	43	unsigned long goal)
	44	{
	45	return memblock_alloc_try_nid_raw(size, align, goal,
	46	MEMBLOCK_ALLOC_ACCESSIBLE, node);
	47	}
	48
	49	void * __meminit vmemmap_alloc_block(unsigned long size, int node)
	50	{
	51	/* If the main allocator is up use that, fallback to bootmem. */
	52	if (slab_is_available()) {
	53	gfp_t gfp_mask = GFP_KERNEL\|__GFP_RETRY_MAYFAIL\|__GFP_NOWARN;
	54	int order = get_order(size);
	55	static bool warned;
	56	struct page *page;
	57
	58	page = alloc_pages_node(node, gfp_mask, order);
	59	if (page)
	60	return page_address(page);
	61
	62	if (!warned) {
	63	warn_alloc(gfp_mask & ~__GFP_NOWARN, NULL,
	64	"vmemmap alloc failure: order:%u", order);
	65	warned = true;
	66	}
	67	return NULL;
	68	} else
	69	return __earlyonly_bootmem_alloc(node, size, size,
	70	__pa(MAX_DMA_ADDRESS));
	71	}
	72
	73	static void * __meminit altmap_alloc_block_buf(unsigned long size,
	74	struct vmem_altmap *altmap);
	75
	76	/* need to make sure size is all the same during early stage */
	77	void * __meminit vmemmap_alloc_block_buf(unsigned long size, int node,
	78	struct vmem_altmap *altmap)
	79	{
	80	void *ptr;
	81
	82	if (altmap)
	83	return altmap_alloc_block_buf(size, altmap);
	84
	85	ptr = sparse_buffer_alloc(size);
	86	if (!ptr)
	87	ptr = vmemmap_alloc_block(size, node);
	88	return ptr;
	89	}
	90
	91	static unsigned long __meminit vmem_altmap_next_pfn(struct vmem_altmap *altmap)
	92	{
	93	return altmap->base_pfn + altmap->reserve + altmap->alloc
	94	+ altmap->align;
	95	}
	96
	97	static unsigned long __meminit vmem_altmap_nr_free(struct vmem_altmap *altmap)
	98	{
	99	unsigned long allocated = altmap->alloc + altmap->align;
	100
	101	if (altmap->free > allocated)
	102	return altmap->free - allocated;
	103	return 0;
	104	}
	105
	106	static void * __meminit altmap_alloc_block_buf(unsigned long size,
	107	struct vmem_altmap *altmap)
	108	{
	109	unsigned long pfn, nr_pfns, nr_align;
	110
	111	if (size & ~PAGE_MASK) {
	112	pr_warn_once("%s: allocations must be multiple of PAGE_SIZE (%ld)\n",
	113	__func__, size);
	114	return NULL;
	115	}
	116
	117	pfn = vmem_altmap_next_pfn(altmap);
	118	nr_pfns = size >> PAGE_SHIFT;
	119	nr_align = 1UL << find_first_bit(&nr_pfns, BITS_PER_LONG);
	120	nr_align = ALIGN(pfn, nr_align) - pfn;
	121	if (nr_pfns + nr_align > vmem_altmap_nr_free(altmap))
	122	return NULL;
	123
	124	altmap->alloc += nr_pfns;
	125	altmap->align += nr_align;
	126	pfn += nr_align;
	127
	128	pr_debug("%s: pfn: %#lx alloc: %ld align: %ld nr: %#lx\n",
	129	__func__, pfn, altmap->alloc, altmap->align, nr_pfns);
	130	return __va(__pfn_to_phys(pfn));
	131	}
	132
	133	void __meminit vmemmap_verify(pte_t *pte, int node,
	134	unsigned long start, unsigned long end)
	135	{
	136	unsigned long pfn = pte_pfn(*pte);
	137	int actual_node = early_pfn_to_nid(pfn);
	138
	139	if (node_distance(actual_node, node) > LOCAL_DISTANCE)
	140	pr_warn_once("[%lx-%lx] potential offnode page_structs\n",
	141	start, end - 1);
	142	}
	143
	144	pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
	145	struct vmem_altmap *altmap,
	146	struct page *reuse)
	147	{
	148	pte_t *pte = pte_offset_kernel(pmd, addr);
	149	if (pte_none(*pte)) {
	150	pte_t entry;
	151	void *p;
	152
	153	if (!reuse) {
	154	p = vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap);
	155	if (!p)
	156	return NULL;
	157	} else {
	158	/*
	159	* When a PTE/PMD entry is freed from the init_mm
	160	* there's a free_pages() call to this page allocated
	161	* above. Thus this get_page() is paired with the
	162	* put_page_testzero() on the freeing path.
	163	* This can only called by certain ZONE_DEVICE path,
	164	* and through vmemmap_populate_compound_pages() when
	165	* slab is available.
	166	*/
	167	get_page(reuse);
	168	p = page_to_virt(reuse);
	169	}
	170	entry = pfn_pte(__pa(p) >> PAGE_SHIFT, PAGE_KERNEL);
	171	set_pte_at(&init_mm, addr, pte, entry);
	172	}
	173	return pte;
	174	}
	175
	176	static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node)
	177	{
	178	void *p = vmemmap_alloc_block(size, node);
	179
	180	if (!p)
	181	return NULL;
	182	memset(p, 0, size);
	183
	184	return p;
	185	}
	186
	187	pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)
	188	{
	189	pmd_t *pmd = pmd_offset(pud, addr);
	190	if (pmd_none(*pmd)) {
	191	void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
	192	if (!p)
	193	return NULL;
	194	pmd_populate_kernel(&init_mm, pmd, p);
	195	}
	196	return pmd;
	197	}
	198
	199	pud_t * __meminit vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node)
	200	{
	201	pud_t *pud = pud_offset(p4d, addr);
	202	if (pud_none(*pud)) {
	203	void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
	204	if (!p)
	205	return NULL;
	206	pud_populate(&init_mm, pud, p);
	207	}
	208	return pud;
	209	}
	210
	211	p4d_t * __meminit vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node)
	212	{
	213	p4d_t *p4d = p4d_offset(pgd, addr);
	214	if (p4d_none(*p4d)) {
	215	void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
	216	if (!p)
	217	return NULL;
	218	p4d_populate(&init_mm, p4d, p);
	219	}
	220	return p4d;
	221	}
	222
	223	pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node)
	224	{
	225	pgd_t *pgd = pgd_offset_k(addr);
	226	if (pgd_none(*pgd)) {
	227	void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
	228	if (!p)
	229	return NULL;
	230	pgd_populate(&init_mm, pgd, p);
	231	}
	232	return pgd;
	233	}
	234
	235	static pte_t * __meminit vmemmap_populate_address(unsigned long addr, int node,
	236	struct vmem_altmap *altmap,
	237	struct page *reuse)
	238	{
	239	pgd_t *pgd;
	240	p4d_t *p4d;
	241	pud_t *pud;
	242	pmd_t *pmd;
	243	pte_t *pte;
	244
	245	pgd = vmemmap_pgd_populate(addr, node);
	246	if (!pgd)
	247	return NULL;
	248	p4d = vmemmap_p4d_populate(pgd, addr, node);
	249	if (!p4d)
	250	return NULL;
	251	pud = vmemmap_pud_populate(p4d, addr, node);
	252	if (!pud)
	253	return NULL;
	254	pmd = vmemmap_pmd_populate(pud, addr, node);
	255	if (!pmd)
	256	return NULL;
	257	pte = vmemmap_pte_populate(pmd, addr, node, altmap, reuse);
	258	if (!pte)
	259	return NULL;
	260	vmemmap_verify(pte, node, addr, addr + PAGE_SIZE);
	261
	262	return pte;
	263	}
	264
	265	static int __meminit vmemmap_populate_range(unsigned long start,
	266	unsigned long end, int node,
	267	struct vmem_altmap *altmap,
	268	struct page *reuse)
	269	{
	270	unsigned long addr = start;
	271	pte_t *pte;
	272
	273	for (; addr < end; addr += PAGE_SIZE) {
	274	pte = vmemmap_populate_address(addr, node, altmap, reuse);
	275	if (!pte)
	276	return -ENOMEM;
	277	}
	278
	279	return 0;
	280	}
	281
	282	int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
	283	int node, struct vmem_altmap *altmap)
	284	{
	285	return vmemmap_populate_range(start, end, node, altmap, NULL);
	286	}
	287
	288	/*
	289	* For compound pages bigger than section size (e.g. x86 1G compound
	290	* pages with 2M subsection size) fill the rest of sections as tail
	291	* pages.
	292	*
	293	* Note that memremap_pages() resets @nr_range value and will increment
	294	* it after each range successful onlining. Thus the value or @nr_range
	295	* at section memmap populate corresponds to the in-progress range
	296	* being onlined here.
	297	*/
	298	static bool __meminit reuse_compound_section(unsigned long start_pfn,
	299	struct dev_pagemap *pgmap)
	300	{
	301	unsigned long nr_pages = pgmap_vmemmap_nr(pgmap);
	302	unsigned long offset = start_pfn -
	303	PHYS_PFN(pgmap->ranges[pgmap->nr_range].start);
	304
	305	return !IS_ALIGNED(offset, nr_pages) && nr_pages > PAGES_PER_SUBSECTION;
	306	}
	307
	308	static pte_t * __meminit compound_section_tail_page(unsigned long addr)
	309	{
	310	pte_t *pte;
	311
	312	addr -= PAGE_SIZE;
	313
	314	/*
	315	* Assuming sections are populated sequentially, the previous section's
	316	* page data can be reused.
	317	*/
	318	pte = pte_offset_kernel(pmd_off_k(addr), addr);
	319	if (!pte)
	320	return NULL;
	321
	322	return pte;
	323	}
	324
	325	static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn,
	326	unsigned long start,
	327	unsigned long end, int node,
	328	struct dev_pagemap *pgmap)
	329	{
	330	unsigned long size, addr;
	331	pte_t *pte;
	332	int rc;
	333
	334	if (reuse_compound_section(start_pfn, pgmap)) {
	335	pte = compound_section_tail_page(start);
	336	if (!pte)
	337	return -ENOMEM;
	338
	339	/*
	340	* Reuse the page that was populated in the prior iteration
	341	* with just tail struct pages.
	342	*/
	343	return vmemmap_populate_range(start, end, node, NULL,
	344	pte_page(*pte));
	345	}
	346
	347	size = min(end - start, pgmap_vmemmap_nr(pgmap) * sizeof(struct page));
	348	for (addr = start; addr < end; addr += size) {
	349	unsigned long next, last = addr + size;
	350
	351	/* Populate the head page vmemmap page */
	352	pte = vmemmap_populate_address(addr, node, NULL, NULL);
	353	if (!pte)
	354	return -ENOMEM;
	355
	356	/* Populate the tail pages vmemmap page */
	357	next = addr + PAGE_SIZE;
	358	pte = vmemmap_populate_address(next, node, NULL, NULL);
	359	if (!pte)
	360	return -ENOMEM;
	361
	362	/*
	363	* Reuse the previous page for the rest of tail pages
	364	* See layout diagram in Documentation/mm/vmemmap_dedup.rst
	365	*/
	366	next += PAGE_SIZE;
	367	rc = vmemmap_populate_range(next, last, node, NULL,
	368	pte_page(*pte));
	369	if (rc)
	370	return -ENOMEM;
	371	}
	372
	373	return 0;
	374	}
	375
	376	struct page * __meminit __populate_section_memmap(unsigned long pfn,
	377	unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
	378	struct dev_pagemap *pgmap)
	379	{
	380	unsigned long start = (unsigned long) pfn_to_page(pfn);
	381	unsigned long end = start + nr_pages * sizeof(struct page);
	382	int r;
	383
	384	if (WARN_ON_ONCE(!IS_ALIGNED(pfn, PAGES_PER_SUBSECTION) \|\|
	385	!IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION)))
	386	return NULL;
	387
	388	if (is_power_of_2(sizeof(struct page)) &&
	389	pgmap && pgmap_vmemmap_nr(pgmap) > 1 && !altmap)
	390	r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap);
	391	else
	392	r = vmemmap_populate(start, end, nid, altmap);
	393
	394	if (r < 0)
	395	return NULL;
	396
	397	return pfn_to_page(pfn);
	398	}