| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Lockless get_user_pages_fast for MIPS |
| * |
| * Copyright (C) 2008 Nick Piggin |
| * Copyright (C) 2008 Novell Inc. |
| * Copyright (C) 2011 Ralf Baechle |
| */ |
| #include <linux/sched.h> |
| #include <linux/mm.h> |
| #include <linux/vmstat.h> |
| #include <linux/highmem.h> |
| #include <linux/swap.h> |
| #include <linux/hugetlb.h> |
| |
| #include <asm/cpu-features.h> |
| #include <asm/pgtable.h> |
| |
| static inline pte_t gup_get_pte(pte_t *ptep) |
| { |
| #if defined(CONFIG_PHYS_ADDR_T_64BIT) && defined(CONFIG_CPU_MIPS32) |
| pte_t pte; |
| |
| retry: |
| pte.pte_low = ptep->pte_low; |
| smp_rmb(); |
| pte.pte_high = ptep->pte_high; |
| smp_rmb(); |
| if (unlikely(pte.pte_low != ptep->pte_low)) |
| goto retry; |
| |
| return pte; |
| #else |
| return READ_ONCE(*ptep); |
| #endif |
| } |
| |
| static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, |
| int write, struct page **pages, int *nr) |
| { |
| pte_t *ptep = pte_offset_map(&pmd, addr); |
| do { |
| pte_t pte = gup_get_pte(ptep); |
| struct page *page; |
| |
| if (!pte_present(pte) || |
| pte_special(pte) || (write && !pte_write(pte))) { |
| pte_unmap(ptep); |
| return 0; |
| } |
| VM_BUG_ON(!pfn_valid(pte_pfn(pte))); |
| page = pte_page(pte); |
| get_page(page); |
| SetPageReferenced(page); |
| pages[*nr] = page; |
| (*nr)++; |
| |
| } while (ptep++, addr += PAGE_SIZE, addr != end); |
| |
| pte_unmap(ptep - 1); |
| return 1; |
| } |
| |
| static inline void get_head_page_multiple(struct page *page, int nr) |
| { |
| VM_BUG_ON(page != compound_head(page)); |
| VM_BUG_ON(page_count(page) == 0); |
| page_ref_add(page, nr); |
| SetPageReferenced(page); |
| } |
| |
| static int gup_huge_pmd(pmd_t pmd, unsigned long addr, unsigned long end, |
| int write, struct page **pages, int *nr) |
| { |
| pte_t pte = *(pte_t *)&pmd; |
| struct page *head, *page; |
| int refs; |
| |
| if (write && !pte_write(pte)) |
| return 0; |
| /* hugepages are never "special" */ |
| VM_BUG_ON(pte_special(pte)); |
| VM_BUG_ON(!pfn_valid(pte_pfn(pte))); |
| |
| refs = 0; |
| head = pte_page(pte); |
| page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); |
| do { |
| VM_BUG_ON(compound_head(page) != head); |
| pages[*nr] = page; |
| (*nr)++; |
| page++; |
| refs++; |
| } while (addr += PAGE_SIZE, addr != end); |
| |
| get_head_page_multiple(head, refs); |
| return 1; |
| } |
| |
| static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, |
| int write, struct page **pages, int *nr) |
| { |
| unsigned long next; |
| pmd_t *pmdp; |
| |
| pmdp = pmd_offset(&pud, addr); |
| do { |
| pmd_t pmd = *pmdp; |
| |
| next = pmd_addr_end(addr, end); |
| if (pmd_none(pmd)) |
| return 0; |
| if (unlikely(pmd_huge(pmd))) { |
| if (!gup_huge_pmd(pmd, addr, next, write, pages,nr)) |
| return 0; |
| } else { |
| if (!gup_pte_range(pmd, addr, next, write, pages,nr)) |
| return 0; |
| } |
| } while (pmdp++, addr = next, addr != end); |
| |
| return 1; |
| } |
| |
| static int gup_huge_pud(pud_t pud, unsigned long addr, unsigned long end, |
| int write, struct page **pages, int *nr) |
| { |
| pte_t pte = *(pte_t *)&pud; |
| struct page *head, *page; |
| int refs; |
| |
| if (write && !pte_write(pte)) |
| return 0; |
| /* hugepages are never "special" */ |
| VM_BUG_ON(pte_special(pte)); |
| VM_BUG_ON(!pfn_valid(pte_pfn(pte))); |
| |
| refs = 0; |
| head = pte_page(pte); |
| page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); |
| do { |
| VM_BUG_ON(compound_head(page) != head); |
| pages[*nr] = page; |
| (*nr)++; |
| page++; |
| refs++; |
| } while (addr += PAGE_SIZE, addr != end); |
| |
| get_head_page_multiple(head, refs); |
| return 1; |
| } |
| |
| static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, |
| int write, struct page **pages, int *nr) |
| { |
| unsigned long next; |
| pud_t *pudp; |
| |
| pudp = pud_offset(&pgd, addr); |
| do { |
| pud_t pud = *pudp; |
| |
| next = pud_addr_end(addr, end); |
| if (pud_none(pud)) |
| return 0; |
| if (unlikely(pud_huge(pud))) { |
| if (!gup_huge_pud(pud, addr, next, write, pages,nr)) |
| return 0; |
| } else { |
| if (!gup_pmd_range(pud, addr, next, write, pages,nr)) |
| return 0; |
| } |
| } while (pudp++, addr = next, addr != end); |
| |
| return 1; |
| } |
| |
| /* |
| * Like get_user_pages_fast() except its IRQ-safe in that it won't fall |
| * back to the regular GUP. |
| * Note a difference with get_user_pages_fast: this always returns the |
| * number of pages pinned, 0 if no pages were pinned. |
| */ |
| int __get_user_pages_fast(unsigned long start, int nr_pages, int write, |
| struct page **pages) |
| { |
| struct mm_struct *mm = current->mm; |
| unsigned long addr, len, end; |
| unsigned long next; |
| unsigned long flags; |
| pgd_t *pgdp; |
| int nr = 0; |
| |
| start &= PAGE_MASK; |
| addr = start; |
| len = (unsigned long) nr_pages << PAGE_SHIFT; |
| end = start + len; |
| if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, |
| (void __user *)start, len))) |
| return 0; |
| |
| /* |
| * XXX: batch / limit 'nr', to avoid large irq off latency |
| * needs some instrumenting to determine the common sizes used by |
| * important workloads (eg. DB2), and whether limiting the batch |
| * size will decrease performance. |
| * |
| * It seems like we're in the clear for the moment. Direct-IO is |
| * the main guy that batches up lots of get_user_pages, and even |
| * they are limited to 64-at-a-time which is not so many. |
| */ |
| /* |
| * This doesn't prevent pagetable teardown, but does prevent |
| * the pagetables and pages from being freed. |
| * |
| * So long as we atomically load page table pointers versus teardown, |
| * we can follow the address down to the page and take a ref on it. |
| */ |
| local_irq_save(flags); |
| pgdp = pgd_offset(mm, addr); |
| do { |
| pgd_t pgd = *pgdp; |
| |
| next = pgd_addr_end(addr, end); |
| if (pgd_none(pgd)) |
| break; |
| if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) |
| break; |
| } while (pgdp++, addr = next, addr != end); |
| local_irq_restore(flags); |
| |
| return nr; |
| } |
| |
| /** |
| * get_user_pages_fast() - pin user pages in memory |
| * @start: starting user address |
| * @nr_pages: number of pages from start to pin |
| * @write: whether pages will be written to |
| * @pages: array that receives pointers to the pages pinned. |
| * Should be at least nr_pages long. |
| * |
| * Attempt to pin user pages in memory without taking mm->mmap_sem. |
| * If not successful, it will fall back to taking the lock and |
| * calling get_user_pages(). |
| * |
| * Returns number of pages pinned. This may be fewer than the number |
| * requested. If nr_pages is 0 or negative, returns 0. If no pages |
| * were pinned, returns -errno. |
| */ |
| int get_user_pages_fast(unsigned long start, int nr_pages, int write, |
| struct page **pages) |
| { |
| struct mm_struct *mm = current->mm; |
| unsigned long addr, len, end; |
| unsigned long next; |
| pgd_t *pgdp; |
| int ret, nr = 0; |
| |
| start &= PAGE_MASK; |
| addr = start; |
| len = (unsigned long) nr_pages << PAGE_SHIFT; |
| |
| end = start + len; |
| if (end < start || cpu_has_dc_aliases) |
| goto slow_irqon; |
| |
| /* XXX: batch / limit 'nr' */ |
| local_irq_disable(); |
| pgdp = pgd_offset(mm, addr); |
| do { |
| pgd_t pgd = *pgdp; |
| |
| next = pgd_addr_end(addr, end); |
| if (pgd_none(pgd)) |
| goto slow; |
| /* |
| * The FAST_GUP case requires FOLL_WRITE even for pure reads, |
| * because get_user_pages() may need to cause an early COW in |
| * order to avoid confusing the normal COW routines. So only |
| * targets that are already writable are safe to do by just |
| * looking at the page tables. |
| */ |
| if (!gup_pud_range(pgd, addr, next, 1, pages, &nr)) |
| goto slow; |
| } while (pgdp++, addr = next, addr != end); |
| local_irq_enable(); |
| |
| VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT); |
| return nr; |
| slow: |
| local_irq_enable(); |
| |
| slow_irqon: |
| /* Try to get the remaining pages with get_user_pages */ |
| start += nr << PAGE_SHIFT; |
| pages += nr; |
| |
| ret = get_user_pages_unlocked(start, (end - start) >> PAGE_SHIFT, |
| pages, write ? FOLL_WRITE : 0); |
| |
| /* Have to be a bit careful with return values */ |
| if (nr > 0) { |
| if (ret < 0) |
| ret = nr; |
| else |
| ret += nr; |
| } |
| return ret; |
| } |