2010-10-25 16:10:11 +02:00
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/*
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* Lockless get_user_pages_fast for s390
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*
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* Copyright IBM Corp. 2010
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* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
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*/
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/hugetlb.h>
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#include <linux/vmstat.h>
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#include <linux/pagemap.h>
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#include <linux/rwsem.h>
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#include <asm/pgtable.h>
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/*
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* The performance critical leaf functions are made noinline otherwise gcc
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* inlines everything into a single function which results in too much
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* register pressure.
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*/
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static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
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unsigned long end, int write, struct page **pages, int *nr)
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{
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2010-11-10 10:05:51 +01:00
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unsigned long mask;
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2010-10-25 16:10:11 +02:00
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pte_t *ptep, pte;
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struct page *page;
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2010-11-10 10:05:51 +01:00
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mask = (write ? _PAGE_RO : 0) | _PAGE_INVALID | _PAGE_SPECIAL;
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2010-10-25 16:10:11 +02:00
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ptep = ((pte_t *) pmd_deref(pmd)) + pte_index(addr);
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do {
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pte = *ptep;
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barrier();
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2010-11-10 10:05:51 +01:00
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if ((pte_val(pte) & mask) != 0)
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2010-10-25 16:10:11 +02:00
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return 0;
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VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
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page = pte_page(pte);
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if (!page_cache_get_speculative(page))
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return 0;
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if (unlikely(pte_val(pte) != pte_val(*ptep))) {
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put_page(page);
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return 0;
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}
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pages[*nr] = page;
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(*nr)++;
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} while (ptep++, addr += PAGE_SIZE, addr != end);
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return 1;
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}
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2011-11-02 21:37:25 +01:00
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static inline void get_huge_page_tail(struct page *page)
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{
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/*
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* __split_huge_page_refcount() cannot run
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* from under us.
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*/
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VM_BUG_ON(page_mapcount(page) < 0);
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VM_BUG_ON(atomic_read(&page->_count) != 0);
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atomic_inc(&page->_mapcount);
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}
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2010-10-25 16:10:11 +02:00
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static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
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unsigned long end, int write, struct page **pages, int *nr)
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{
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unsigned long mask, result;
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2011-11-02 21:37:25 +01:00
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struct page *head, *page, *tail;
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2010-10-25 16:10:11 +02:00
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int refs;
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result = write ? 0 : _SEGMENT_ENTRY_RO;
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mask = result | _SEGMENT_ENTRY_INV;
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if ((pmd_val(pmd) & mask) != result)
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return 0;
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VM_BUG_ON(!pfn_valid(pmd_val(pmd) >> PAGE_SHIFT));
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refs = 0;
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head = pmd_page(pmd);
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page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
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2011-11-02 21:37:25 +01:00
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tail = page;
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2010-10-25 16:10:11 +02:00
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do {
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VM_BUG_ON(compound_head(page) != head);
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pages[*nr] = page;
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(*nr)++;
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page++;
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refs++;
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} while (addr += PAGE_SIZE, addr != end);
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if (!page_cache_add_speculative(head, refs)) {
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*nr -= refs;
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return 0;
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}
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if (unlikely(pmd_val(pmd) != pmd_val(*pmdp))) {
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*nr -= refs;
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while (refs--)
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put_page(head);
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2011-11-02 21:37:25 +01:00
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} else {
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/*
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* Any tail page need their mapcount reference taken
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* before we return.
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*/
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while (refs--) {
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if (PageTail(tail))
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get_huge_page_tail(tail);
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tail++;
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}
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2010-10-25 16:10:11 +02:00
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}
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return 1;
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}
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static inline int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr,
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unsigned long end, int write, struct page **pages, int *nr)
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{
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unsigned long next;
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pmd_t *pmdp, pmd;
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pmdp = (pmd_t *) pudp;
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#ifdef CONFIG_64BIT
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if ((pud_val(pud) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
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pmdp = (pmd_t *) pud_deref(pud);
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pmdp += pmd_index(addr);
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#endif
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do {
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pmd = *pmdp;
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barrier();
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next = pmd_addr_end(addr, end);
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if (pmd_none(pmd))
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return 0;
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if (unlikely(pmd_huge(pmd))) {
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if (!gup_huge_pmd(pmdp, pmd, addr, next,
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write, pages, nr))
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return 0;
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} else if (!gup_pte_range(pmdp, pmd, addr, next,
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write, pages, nr))
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return 0;
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} while (pmdp++, addr = next, addr != end);
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return 1;
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}
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static inline int gup_pud_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr,
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unsigned long end, int write, struct page **pages, int *nr)
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{
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unsigned long next;
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pud_t *pudp, pud;
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pudp = (pud_t *) pgdp;
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#ifdef CONFIG_64BIT
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if ((pgd_val(pgd) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R2)
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pudp = (pud_t *) pgd_deref(pgd);
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pudp += pud_index(addr);
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#endif
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do {
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pud = *pudp;
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barrier();
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next = pud_addr_end(addr, end);
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if (pud_none(pud))
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return 0;
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if (!gup_pmd_range(pudp, pud, addr, next, write, pages, nr))
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return 0;
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} while (pudp++, addr = next, addr != end);
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return 1;
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}
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/**
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* get_user_pages_fast() - pin user pages in memory
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* @start: starting user address
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* @nr_pages: number of pages from start to pin
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* @write: whether pages will be written to
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* @pages: array that receives pointers to the pages pinned.
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* Should be at least nr_pages long.
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*
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* Attempt to pin user pages in memory without taking mm->mmap_sem.
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* If not successful, it will fall back to taking the lock and
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* calling get_user_pages().
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*
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* Returns number of pages pinned. This may be fewer than the number
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* requested. If nr_pages is 0 or negative, returns 0. If no pages
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* were pinned, returns -errno.
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*/
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int get_user_pages_fast(unsigned long start, int nr_pages, int write,
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struct page **pages)
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{
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struct mm_struct *mm = current->mm;
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unsigned long addr, len, end;
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unsigned long next;
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pgd_t *pgdp, pgd;
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int nr = 0;
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start &= PAGE_MASK;
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addr = start;
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len = (unsigned long) nr_pages << PAGE_SHIFT;
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end = start + len;
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if (end < start)
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goto slow_irqon;
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/*
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* local_irq_disable() doesn't prevent pagetable teardown, but does
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* prevent the pagetables from being freed on s390.
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*
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* So long as we atomically load page table pointers versus teardown,
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* we can follow the address down to the the page and take a ref on it.
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*/
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local_irq_disable();
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pgdp = pgd_offset(mm, addr);
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do {
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pgd = *pgdp;
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barrier();
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next = pgd_addr_end(addr, end);
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if (pgd_none(pgd))
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goto slow;
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if (!gup_pud_range(pgdp, pgd, addr, next, write, pages, &nr))
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goto slow;
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} while (pgdp++, addr = next, addr != end);
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local_irq_enable();
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VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
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return nr;
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{
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int ret;
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slow:
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local_irq_enable();
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slow_irqon:
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/* Try to get the remaining pages with get_user_pages */
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start += nr << PAGE_SHIFT;
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pages += nr;
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down_read(&mm->mmap_sem);
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ret = get_user_pages(current, mm, start,
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(end - start) >> PAGE_SHIFT, write, 0, pages, NULL);
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up_read(&mm->mmap_sem);
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/* Have to be a bit careful with return values */
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if (nr > 0) {
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if (ret < 0)
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ret = nr;
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else
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ret += nr;
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}
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return ret;
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}
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}
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