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![Kirill A. Shutemov](/assets/img/avatar_default.png)
With new refcounting we don't need to mark PMDs splitting. Let's drop code to handle this. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Steve Capper <steve.capper@linaro.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
253 lines
5.5 KiB
C
253 lines
5.5 KiB
C
/*
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* Lockless get_user_pages_fast for sparc, cribbed from powerpc
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*
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* Copyright (C) 2008 Nick Piggin
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* Copyright (C) 2008 Novell Inc.
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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/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 noinline int gup_pte_range(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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pte_t *ptep;
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if (tlb_type == hypervisor) {
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result = _PAGE_PRESENT_4V|_PAGE_P_4V;
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if (write)
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result |= _PAGE_WRITE_4V;
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} else {
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result = _PAGE_PRESENT_4U|_PAGE_P_4U;
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if (write)
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result |= _PAGE_WRITE_4U;
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}
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mask = result | _PAGE_SPECIAL;
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ptep = pte_offset_kernel(&pmd, addr);
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do {
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struct page *page, *head;
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pte_t pte = *ptep;
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if ((pte_val(pte) & mask) != result)
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return 0;
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VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
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/* The hugepage case is simplified on sparc64 because
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* we encode the sub-page pfn offsets into the
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* hugepage PTEs. We could optimize this in the future
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* use page_cache_add_speculative() for the hugepage case.
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*/
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page = pte_page(pte);
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head = compound_head(page);
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if (!page_cache_get_speculative(head))
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return 0;
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if (unlikely(pte_val(pte) != pte_val(*ptep))) {
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put_page(head);
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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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static 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,
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int *nr)
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{
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struct page *head, *page;
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int refs;
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if (!(pmd_val(pmd) & _PAGE_VALID))
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return 0;
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if (write && !pmd_write(pmd))
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return 0;
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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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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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return 0;
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}
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return 1;
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}
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static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
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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;
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pmdp = pmd_offset(&pud, addr);
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do {
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pmd_t pmd = *pmdp;
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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_large(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(pmd, addr, next, write,
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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 int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
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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;
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pudp = pud_offset(&pgd, addr);
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do {
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pud_t pud = *pudp;
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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(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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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, flags;
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pgd_t *pgdp;
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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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local_irq_save(flags);
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pgdp = pgd_offset(mm, addr);
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do {
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pgd_t pgd = *pgdp;
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next = pgd_addr_end(addr, end);
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if (pgd_none(pgd))
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break;
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if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
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break;
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} while (pgdp++, addr = next, addr != end);
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local_irq_restore(flags);
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return nr;
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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;
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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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/*
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* XXX: batch / limit 'nr', to avoid large irq off latency
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* needs some instrumenting to determine the common sizes used by
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* important workloads (eg. DB2), and whether limiting the batch size
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* will decrease performance.
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*
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* It seems like we're in the clear for the moment. Direct-IO is
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* the main guy that batches up lots of get_user_pages, and even
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* they are limited to 64-at-a-time which is not so many.
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*/
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/*
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* This doesn't prevent pagetable teardown, but does prevent
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* the pagetables from being freed on sparc.
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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_t pgd = *pgdp;
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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(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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/* 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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ret = get_user_pages_unlocked(current, mm, start,
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(end - start) >> PAGE_SHIFT, write, 0, pages);
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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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