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Date: Mon, 13 Jun 2022 10:15:00 +0200
From: Oscar Salvador <osalvador@...e.de>
To: Muchun Song <songmuchun@...edance.com>
Cc: mike.kravetz@...cle.com, david@...hat.com,
akpm@...ux-foundation.org, corbet@....net, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH 4/6] mm: hugetlb_vmemmap: move vmemmap code related to
HugeTLB to hugetlb_vmemmap.c
On Mon, Jun 13, 2022 at 02:35:10PM +0800, Muchun Song wrote:
> When I first introduced vmemmap manipulation functions related to HugeTLB,
> I thought those functions may be reused by other modules (e.g. using
> similar approach to optimize vmemmap pages, unfortunately, the DAX used the
> same approach but does not use those functions). After two years, we didn't
> see any other users. So move those functions to hugetlb_vmemmap.c.
>
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
Reviewed-by: Oscar Salvador <osalvador@...e.de>
> ---
> include/linux/mm.h | 7 -
> mm/hugetlb_vmemmap.c | 391 ++++++++++++++++++++++++++++++++++++++++++++++++++-
> mm/sparse-vmemmap.c | 391 ---------------------------------------------------
> 3 files changed, 390 insertions(+), 399 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 623c2ee8330a..152d0eefe5aa 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3208,13 +3208,6 @@ static inline void print_vma_addr(char *prefix, unsigned long rip)
> }
> #endif
>
> -#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
> -int vmemmap_remap_free(unsigned long start, unsigned long end,
> - unsigned long reuse);
> -int vmemmap_remap_alloc(unsigned long start, unsigned long end,
> - unsigned long reuse, gfp_t gfp_mask);
> -#endif
> -
> 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,
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index c10540993577..abdf441215bb 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -10,9 +10,31 @@
> */
> #define pr_fmt(fmt) "HugeTLB: " fmt
>
> -#include <linux/memory_hotplug.h>
> +#include <linux/pgtable.h>
> +#include <linux/bootmem_info.h>
> +#include <asm/pgalloc.h>
> +#include <asm/tlbflush.h>
> #include "hugetlb_vmemmap.h"
>
> +/**
> + * 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;
> +};
> +
> /*
> * There are a lot of struct page structures associated with each HugeTLB page.
> * For tail pages, the value of compound_head is the same. So we can reuse first
> @@ -23,6 +45,373 @@
> #define RESERVE_VMEMMAP_NR 1U
> #define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT)
>
> +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(!PAGE_ALIGNED(start));
> + VM_BUG_ON(!PAGE_ALIGNED(end));
> +
> + 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.
> + */
> +static 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.
> + */
> +static 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;
> +}
> +
> DEFINE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key);
> EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key);
>
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 49cb15cbe590..473effcb2285 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -27,400 +27,9 @@
> #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(!PAGE_ALIGNED(start));
> - VM_BUG_ON(!PAGE_ALIGNED(end));
> -
> - 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
> --
> 2.11.0
>
>
--
Oscar Salvador
SUSE Labs
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