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We can do that in the __free_hugepage(). Signed-off-by: Muchun Song --- mm/hugetlb.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 109 insertions(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index ded7f0fbde35..8295911fe76e 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1307,6 +1307,8 @@ static void __free_hugepage(struct hstate *h, struct page *page); * reserve at least 2 pages as vmemmap areas. */ #define RESERVE_VMEMMAP_NR 2U +#define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT) +#define GFP_VMEMMAP_PAGE (GFP_KERNEL | __GFP_NOFAIL | __GFP_MEMALLOC) #define page_huge_pte(page) ((page)->pmd_huge_pte) @@ -1490,7 +1492,7 @@ static void __free_huge_page_pmd_vmemmap(struct hstate *h, pmd_t *pmd, struct list_head *free_pages) { unsigned long next; - unsigned long start = addr + RESERVE_VMEMMAP_NR * PAGE_SIZE; + unsigned long start = addr + RESERVE_VMEMMAP_SIZE; unsigned long end = addr + vmemmap_pages_size_per_hpage(h); struct page *reuse = NULL; @@ -1578,6 +1580,106 @@ static void free_huge_page_vmemmap(struct hstate *h, struct page *head) free_vmemmap_page_list(&free_pages); } +static void __remap_huge_page_pte_vmemmap(struct page *reuse, pte_t *ptep, + unsigned long start, + unsigned int nr_remap, + struct list_head *remap_pages) +{ + pgprot_t pgprot = PAGE_KERNEL; + void *from = (void *)page_private(reuse); + unsigned long addr, end = start + (nr_remap << PAGE_SHIFT); + + for (addr = start; addr < end; addr += PAGE_SIZE) { + void *to; + struct page *page; + pte_t entry, old = *ptep; + + page = list_first_entry_or_null(remap_pages, struct page, lru); + list_del(&page->lru); + to = page_to_virt(page); + copy_page(to, from); + + /* + * Make sure that any data that writes to the @to is made + * visible to the physical page. + */ + flush_kernel_vmap_range(to, PAGE_SIZE); + + prepare_vmemmap_page(page); + + entry = mk_pte(page, pgprot); + set_pte_at(&init_mm, addr, ptep++, entry); + + VM_BUG_ON(!pte_present(old) || pte_page(old) != reuse); + } +} + +static void __remap_huge_page_pmd_vmemmap(struct hstate *h, pmd_t *pmd, + unsigned long addr, + struct list_head *remap_pages) +{ + unsigned long next; + unsigned long start = addr + RESERVE_VMEMMAP_NR * PAGE_SIZE; + unsigned long end = addr + vmemmap_pages_size_per_hpage(h); + struct page *reuse = NULL; + + addr = start; + do { + unsigned int nr_pages; + pte_t *ptep; + + ptep = pte_offset_kernel(pmd, addr); + if (!reuse) { + reuse = pte_page(ptep[-1]); + set_page_private(reuse, addr - PAGE_SIZE); + } + + next = vmemmap_hpage_addr_end(addr, end); + nr_pages = (next - addr) >> PAGE_SHIFT; + __remap_huge_page_pte_vmemmap(reuse, ptep, addr, nr_pages, + remap_pages); + } while (pmd++, addr = next, addr != end); + + flush_tlb_kernel_range(start, end); +} + +static inline void alloc_vmemmap_pages(struct hstate *h, struct list_head *list) +{ + int i; + + for (i = 0; i < free_vmemmap_pages_per_hpage(h); i++) { + struct page *page; + + /* This should not fail */ + page = alloc_page(GFP_VMEMMAP_PAGE); + list_add_tail(&page->lru, list); + } +} + +static void alloc_huge_page_vmemmap(struct hstate *h, struct page *head) +{ + pmd_t *pmd; + spinlock_t *ptl; + LIST_HEAD(remap_pages); + + if (!free_vmemmap_pages_per_hpage(h)) + return; + + alloc_vmemmap_pages(h, &remap_pages); + + pmd = vmemmap_to_pmd(head); + ptl = vmemmap_pmd_lock(pmd); + __remap_huge_page_pmd_vmemmap(h, pmd, (unsigned long)head, + &remap_pages); + if (!freed_vmemmap_hpage_dec(pmd_page(*pmd))) { + /* + * Todo: + * Merge pte to huge pmd if it has ever been split. + */ + } + spin_unlock(ptl); +} + /* * As update_and_free_page() is be called from a non-task context(and hold * hugetlb_lock), we can defer the actual freeing in a workqueue to prevent @@ -1653,6 +1755,10 @@ static inline void free_huge_page_vmemmap(struct hstate *h, struct page *head) { } +static inline void alloc_huge_page_vmemmap(struct hstate *h, struct page *head) +{ +} + static inline void __update_and_free_page(struct hstate *h, struct page *page) { __free_hugepage(h, page); @@ -1685,6 +1791,8 @@ static void __free_hugepage(struct hstate *h, struct page *page) { int i; + alloc_huge_page_vmemmap(h, page); + for (i = 0; i < pages_per_huge_page(h); i++) { page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced | 1 << PG_dirty |