linux-stable/mm/sparse-vmemmap.c
Joao Martins 4917f55b4e mm/sparse-vmemmap: improve memory savings for compound devmaps
A compound devmap is a dev_pagemap with @vmemmap_shift > 0 and it means
that pages are mapped at a given huge page alignment and utilize uses
compound pages as opposed to order-0 pages.

Take advantage of the fact that most tail pages look the same (except the
first two) to minimize struct page overhead.  Allocate a separate page for
the vmemmap area which contains the head page and separate for the next 64
pages.  The rest of the subsections then reuse this tail vmemmap page to
initialize the rest of the tail pages.

Sections are arch-dependent (e.g.  on x86 it's 64M, 128M or 512M) and when
initializing compound devmap with big enough @vmemmap_shift (e.g.  1G PUD)
it may cross multiple sections.  The vmemmap code needs to consult @pgmap
so that multiple sections that all map the same tail data can refer back
to the first copy of that data for a given gigantic page.

On compound devmaps with 2M align, this mechanism lets 6 pages be saved
out of the 8 necessary PFNs necessary to set the subsection's 512 struct
pages being mapped.  On a 1G compound devmap it saves 4094 pages.

Altmap isn't supported yet, given various restrictions in altmap pfn
allocator, thus fallback to the already in use vmemmap_populate().  It is
worth noting that altmap for devmap mappings was there to relieve the
pressure of inordinate amounts of memmap space to map terabytes of pmem. 
With compound pages the motivation for altmaps for pmem gets reduced.

Link: https://lkml.kernel.org/r/20220420155310.9712-5-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-04-28 23:16:16 -07:00

789 lines
20 KiB
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 <linux/pgtable.h>
#include <linux/bootmem_info.h>
#include <asm/dma.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
/**
* struct vmemmap_remap_walk - walk vmemmap page table
*
* @remap_pte: called for each lowest-level entry (PTE).
* @nr_walked: the number of walked pte.
* @reuse_page: the page which is reused for the tail vmemmap pages.
* @reuse_addr: the virtual address of the @reuse_page page.
* @vmemmap_pages: the list head of the vmemmap pages that can be freed
* or is mapped from.
*/
struct vmemmap_remap_walk {
void (*remap_pte)(pte_t *pte, unsigned long addr,
struct vmemmap_remap_walk *walk);
unsigned long nr_walked;
struct page *reuse_page;
unsigned long reuse_addr;
struct list_head *vmemmap_pages;
};
static int __split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
{
pmd_t __pmd;
int i;
unsigned long addr = start;
struct page *page = pmd_page(*pmd);
pte_t *pgtable = pte_alloc_one_kernel(&init_mm);
if (!pgtable)
return -ENOMEM;
pmd_populate_kernel(&init_mm, &__pmd, pgtable);
for (i = 0; i < PMD_SIZE / PAGE_SIZE; i++, addr += PAGE_SIZE) {
pte_t entry, *pte;
pgprot_t pgprot = PAGE_KERNEL;
entry = mk_pte(page + i, pgprot);
pte = pte_offset_kernel(&__pmd, addr);
set_pte_at(&init_mm, addr, pte, entry);
}
spin_lock(&init_mm.page_table_lock);
if (likely(pmd_leaf(*pmd))) {
/* Make pte visible before pmd. See comment in pmd_install(). */
smp_wmb();
pmd_populate_kernel(&init_mm, pmd, pgtable);
flush_tlb_kernel_range(start, start + PMD_SIZE);
} else {
pte_free_kernel(&init_mm, pgtable);
}
spin_unlock(&init_mm.page_table_lock);
return 0;
}
static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
{
int leaf;
spin_lock(&init_mm.page_table_lock);
leaf = pmd_leaf(*pmd);
spin_unlock(&init_mm.page_table_lock);
if (!leaf)
return 0;
return __split_vmemmap_huge_pmd(pmd, start);
}
static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
pte_t *pte = pte_offset_kernel(pmd, addr);
/*
* The reuse_page is found 'first' in table walk before we start
* remapping (which is calling @walk->remap_pte).
*/
if (!walk->reuse_page) {
walk->reuse_page = pte_page(*pte);
/*
* Because the reuse address is part of the range that we are
* walking, skip the reuse address range.
*/
addr += PAGE_SIZE;
pte++;
walk->nr_walked++;
}
for (; addr != end; addr += PAGE_SIZE, pte++) {
walk->remap_pte(pte, addr, walk);
walk->nr_walked++;
}
}
static int vmemmap_pmd_range(pud_t *pud, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
pmd_t *pmd;
unsigned long next;
pmd = pmd_offset(pud, addr);
do {
int ret;
ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK);
if (ret)
return ret;
next = pmd_addr_end(addr, end);
vmemmap_pte_range(pmd, addr, next, walk);
} while (pmd++, addr = next, addr != end);
return 0;
}
static int vmemmap_pud_range(p4d_t *p4d, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
pud_t *pud;
unsigned long next;
pud = pud_offset(p4d, addr);
do {
int ret;
next = pud_addr_end(addr, end);
ret = vmemmap_pmd_range(pud, addr, next, walk);
if (ret)
return ret;
} while (pud++, addr = next, addr != end);
return 0;
}
static int vmemmap_p4d_range(pgd_t *pgd, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
p4d_t *p4d;
unsigned long next;
p4d = p4d_offset(pgd, addr);
do {
int ret;
next = p4d_addr_end(addr, end);
ret = vmemmap_pud_range(p4d, addr, next, walk);
if (ret)
return ret;
} while (p4d++, addr = next, addr != end);
return 0;
}
static int vmemmap_remap_range(unsigned long start, unsigned long end,
struct vmemmap_remap_walk *walk)
{
unsigned long addr = start;
unsigned long next;
pgd_t *pgd;
VM_BUG_ON(!IS_ALIGNED(start, PAGE_SIZE));
VM_BUG_ON(!IS_ALIGNED(end, PAGE_SIZE));
pgd = pgd_offset_k(addr);
do {
int ret;
next = pgd_addr_end(addr, end);
ret = vmemmap_p4d_range(pgd, addr, next, walk);
if (ret)
return ret;
} while (pgd++, addr = next, addr != end);
/*
* We only change the mapping of the vmemmap virtual address range
* [@start + PAGE_SIZE, end), so we only need to flush the TLB which
* belongs to the range.
*/
flush_tlb_kernel_range(start + PAGE_SIZE, end);
return 0;
}
/*
* Free a vmemmap page. A vmemmap page can be allocated from the memblock
* allocator or buddy allocator. If the PG_reserved flag is set, it means
* that it allocated from the memblock allocator, just free it via the
* free_bootmem_page(). Otherwise, use __free_page().
*/
static inline void free_vmemmap_page(struct page *page)
{
if (PageReserved(page))
free_bootmem_page(page);
else
__free_page(page);
}
/* Free a list of the vmemmap pages */
static void free_vmemmap_page_list(struct list_head *list)
{
struct page *page, *next;
list_for_each_entry_safe(page, next, list, lru) {
list_del(&page->lru);
free_vmemmap_page(page);
}
}
static void vmemmap_remap_pte(pte_t *pte, unsigned long addr,
struct vmemmap_remap_walk *walk)
{
/*
* Remap the tail pages as read-only to catch illegal write operation
* to the tail pages.
*/
pgprot_t pgprot = PAGE_KERNEL_RO;
pte_t entry = mk_pte(walk->reuse_page, pgprot);
struct page *page = pte_page(*pte);
list_add_tail(&page->lru, walk->vmemmap_pages);
set_pte_at(&init_mm, addr, pte, entry);
}
/*
* How many struct page structs need to be reset. When we reuse the head
* struct page, the special metadata (e.g. page->flags or page->mapping)
* cannot copy to the tail struct page structs. The invalid value will be
* checked in the free_tail_pages_check(). In order to avoid the message
* of "corrupted mapping in tail page". We need to reset at least 3 (one
* head struct page struct and two tail struct page structs) struct page
* structs.
*/
#define NR_RESET_STRUCT_PAGE 3
static inline void reset_struct_pages(struct page *start)
{
int i;
struct page *from = start + NR_RESET_STRUCT_PAGE;
for (i = 0; i < NR_RESET_STRUCT_PAGE; i++)
memcpy(start + i, from, sizeof(*from));
}
static void vmemmap_restore_pte(pte_t *pte, unsigned long addr,
struct vmemmap_remap_walk *walk)
{
pgprot_t pgprot = PAGE_KERNEL;
struct page *page;
void *to;
BUG_ON(pte_page(*pte) != walk->reuse_page);
page = list_first_entry(walk->vmemmap_pages, struct page, lru);
list_del(&page->lru);
to = page_to_virt(page);
copy_page(to, (void *)walk->reuse_addr);
reset_struct_pages(to);
set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot));
}
/**
* vmemmap_remap_free - remap the vmemmap virtual address range [@start, @end)
* to the page which @reuse is mapped to, then free vmemmap
* which the range are mapped to.
* @start: start address of the vmemmap virtual address range that we want
* to remap.
* @end: end address of the vmemmap virtual address range that we want to
* remap.
* @reuse: reuse address.
*
* Return: %0 on success, negative error code otherwise.
*/
int vmemmap_remap_free(unsigned long start, unsigned long end,
unsigned long reuse)
{
int ret;
LIST_HEAD(vmemmap_pages);
struct vmemmap_remap_walk walk = {
.remap_pte = vmemmap_remap_pte,
.reuse_addr = reuse,
.vmemmap_pages = &vmemmap_pages,
};
/*
* In order to make remapping routine most efficient for the huge pages,
* the routine of vmemmap page table walking has the following rules
* (see more details from the vmemmap_pte_range()):
*
* - The range [@start, @end) and the range [@reuse, @reuse + PAGE_SIZE)
* should be continuous.
* - The @reuse address is part of the range [@reuse, @end) that we are
* walking which is passed to vmemmap_remap_range().
* - The @reuse address is the first in the complete range.
*
* So we need to make sure that @start and @reuse meet the above rules.
*/
BUG_ON(start - reuse != PAGE_SIZE);
mmap_read_lock(&init_mm);
ret = vmemmap_remap_range(reuse, end, &walk);
if (ret && walk.nr_walked) {
end = reuse + walk.nr_walked * PAGE_SIZE;
/*
* vmemmap_pages contains pages from the previous
* vmemmap_remap_range call which failed. These
* are pages which were removed from the vmemmap.
* They will be restored in the following call.
*/
walk = (struct vmemmap_remap_walk) {
.remap_pte = vmemmap_restore_pte,
.reuse_addr = reuse,
.vmemmap_pages = &vmemmap_pages,
};
vmemmap_remap_range(reuse, end, &walk);
}
mmap_read_unlock(&init_mm);
free_vmemmap_page_list(&vmemmap_pages);
return ret;
}
static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
gfp_t gfp_mask, struct list_head *list)
{
unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
int nid = page_to_nid((struct page *)start);
struct page *page, *next;
while (nr_pages--) {
page = alloc_pages_node(nid, gfp_mask, 0);
if (!page)
goto out;
list_add_tail(&page->lru, list);
}
return 0;
out:
list_for_each_entry_safe(page, next, list, lru)
__free_pages(page, 0);
return -ENOMEM;
}
/**
* vmemmap_remap_alloc - remap the vmemmap virtual address range [@start, end)
* to the page which is from the @vmemmap_pages
* respectively.
* @start: start address of the vmemmap virtual address range that we want
* to remap.
* @end: end address of the vmemmap virtual address range that we want to
* remap.
* @reuse: reuse address.
* @gfp_mask: GFP flag for allocating vmemmap pages.
*
* Return: %0 on success, negative error code otherwise.
*/
int vmemmap_remap_alloc(unsigned long start, unsigned long end,
unsigned long reuse, gfp_t gfp_mask)
{
LIST_HEAD(vmemmap_pages);
struct vmemmap_remap_walk walk = {
.remap_pte = vmemmap_restore_pte,
.reuse_addr = reuse,
.vmemmap_pages = &vmemmap_pages,
};
/* See the comment in the vmemmap_remap_free(). */
BUG_ON(start - reuse != PAGE_SIZE);
if (alloc_vmemmap_page_list(start, end, gfp_mask, &vmemmap_pages))
return -ENOMEM;
mmap_read_lock(&init_mm);
vmemmap_remap_range(reuse, end, &walk);
mmap_read_unlock(&init_mm);
return 0;
}
#endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */
/*
* 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("[%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 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 = addr, 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/vm/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);
}