x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation

This patch provides all required callbacks required by the generic
get_user_pages_fast() code and switches x86 over - and removes
the platform specific implementation.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Aneesh Kumar K . V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dann Frazier <dann.frazier@canonical.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170316213906.89528-1-kirill.shutemov@linux.intel.com
[ Minor readability edits. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 0 insertions, 496 deletions

diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
deleted file mode 100644
index 456dfdfd2249..000000000000
--- a/arch/x86/mm/gup.c
+++ /dev/null
@@ -1,496 +0,0 @@
-/*
- * Lockless get_user_pages_fast for x86
- *
- * Copyright (C) 2008 Nick Piggin
- * Copyright (C) 2008 Novell Inc.
- */
-#include <linux/sched.h>
-#include <linux/mm.h>
-#include <linux/vmstat.h>
-#include <linux/highmem.h>
-#include <linux/swap.h>
-#include <linux/memremap.h>
-
-#include <asm/mmu_context.h>
-#include <asm/pgtable.h>
-
-static inline pte_t gup_get_pte(pte_t *ptep)
-{
-#ifndef CONFIG_X86_PAE
-	return READ_ONCE(*ptep);
-#else
-	/*
-	 * With get_user_pages_fast, we walk down the pagetables without taking
-	 * any locks.  For this we would like to load the pointers atomically,
-	 * but that is not possible (without expensive cmpxchg8b) on PAE.  What
-	 * we do have is the guarantee that a pte will only either go from not
-	 * present to present, or present to not present or both -- it will not
-	 * switch to a completely different present page without a TLB flush in
-	 * between; something that we are blocking by holding interrupts off.
-	 *
-	 * Setting ptes from not present to present goes:
-	 * ptep->pte_high = h;
-	 * smp_wmb();
-	 * ptep->pte_low = l;
-	 *
-	 * And present to not present goes:
-	 * ptep->pte_low = 0;
-	 * smp_wmb();
-	 * ptep->pte_high = 0;
-	 *
-	 * We must ensure here that the load of pte_low sees l iff pte_high
-	 * sees h. We load pte_high *after* loading pte_low, which ensures we
-	 * don't see an older value of pte_high.  *Then* we recheck pte_low,
-	 * which ensures that we haven't picked up a changed pte high. We might
-	 * have got rubbish values from pte_low and pte_high, but we are
-	 * guaranteed that pte_low will not have the present bit set *unless*
-	 * it is 'l'. And get_user_pages_fast only operates on present ptes, so
-	 * we're safe.
-	 *
-	 * gup_get_pte should not be used or copied outside gup.c without being
-	 * very careful -- it does not atomically load the pte or anything that
-	 * is likely to be useful for you.
-	 */
-	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;
-#endif
-}
-
-static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
-{
-	while ((*nr) - nr_start) {
-		struct page *page = pages[--(*nr)];
-
-		ClearPageReferenced(page);
-		put_page(page);
-	}
-}
-
-/*
- * 'pteval' can come from a pte, pmd, pud or p4d.  We only check
- * _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which are the
- * same value on all 4 types.
- */
-static inline int pte_allows_gup(unsigned long pteval, int write)
-{
-	unsigned long need_pte_bits = _PAGE_PRESENT|_PAGE_USER;
-
-	if (write)
-		need_pte_bits |= _PAGE_RW;
-
-	if ((pteval & need_pte_bits) != need_pte_bits)
-		return 0;
-
-	/* Check memory protection keys permissions. */
-	if (!__pkru_allows_pkey(pte_flags_pkey(pteval), write))
-		return 0;
-
-	return 1;
-}
-
-/*
- * The performance critical leaf functions are made noinline otherwise gcc
- * inlines everything into a single function which results in too much
- * register pressure.
- */
-static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
-		unsigned long end, int write, struct page **pages, int *nr)
-{
-	struct dev_pagemap *pgmap = NULL;
-	int nr_start = *nr, ret = 0;
-	pte_t *ptep, *ptem;
-
-	/*
-	 * Keep the original mapped PTE value (ptem) around since we
-	 * might increment ptep off the end of the page when finishing
-	 * our loop iteration.
-	 */
-	ptem = ptep = pte_offset_map(&pmd, addr);
-	do {
-		pte_t pte = gup_get_pte(ptep);
-		struct page *page;
-
-		/* Similar to the PMD case, NUMA hinting must take slow path */
-		if (pte_protnone(pte))
-			break;
-
-		if (!pte_allows_gup(pte_val(pte), write))
-			break;
-
-		if (pte_devmap(pte)) {
-			pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
-			if (unlikely(!pgmap)) {
-				undo_dev_pagemap(nr, nr_start, pages);
-				break;
-			}
-		} else if (pte_special(pte))
-			break;
-
-		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
-		page = pte_page(pte);
-		get_page(page);
-		put_dev_pagemap(pgmap);
-		SetPageReferenced(page);
-		pages[*nr] = page;
-		(*nr)++;
-
-	} while (ptep++, addr += PAGE_SIZE, addr != end);
-	if (addr == end)
-		ret = 1;
-	pte_unmap(ptem);
-
-	return ret;
-}
-
-static inline void get_head_page_multiple(struct page *page, int nr)
-{
-	VM_BUG_ON_PAGE(page != compound_head(page), page);
-	VM_BUG_ON_PAGE(page_count(page) == 0, page);
-	page_ref_add(page, nr);
-	SetPageReferenced(page);
-}
-
-static int __gup_device_huge(unsigned long pfn, unsigned long addr,
-		unsigned long end, struct page **pages, int *nr)
-{
-	int nr_start = *nr;
-	struct dev_pagemap *pgmap = NULL;
-
-	do {
-		struct page *page = pfn_to_page(pfn);
-
-		pgmap = get_dev_pagemap(pfn, pgmap);
-		if (unlikely(!pgmap)) {
-			undo_dev_pagemap(nr, nr_start, pages);
-			return 0;
-		}
-		SetPageReferenced(page);
-		pages[*nr] = page;
-		get_page(page);
-		put_dev_pagemap(pgmap);
-		(*nr)++;
-		pfn++;
-	} while (addr += PAGE_SIZE, addr != end);
-	return 1;
-}
-
-static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
-		unsigned long end, struct page **pages, int *nr)
-{
-	unsigned long fault_pfn;
-
-	fault_pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
-	return __gup_device_huge(fault_pfn, addr, end, pages, nr);
-}
-
-static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
-		unsigned long end, struct page **pages, int *nr)
-{
-	unsigned long fault_pfn;
-
-	fault_pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
-	return __gup_device_huge(fault_pfn, addr, end, pages, nr);
-}
-
-static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
-		unsigned long end, int write, struct page **pages, int *nr)
-{
-	struct page *head, *page;
-	int refs;
-
-	if (!pte_allows_gup(pmd_val(pmd), write))
-		return 0;
-
-	VM_BUG_ON(!pfn_valid(pmd_pfn(pmd)));
-	if (pmd_devmap(pmd))
-		return __gup_device_huge_pmd(pmd, addr, end, pages, nr);
-
-	/* hugepages are never "special" */
-	VM_BUG_ON(pmd_flags(pmd) & _PAGE_SPECIAL);
-
-	refs = 0;
-	head = pmd_page(pmd);
-	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
-	do {
-		VM_BUG_ON_PAGE(compound_head(page) != head, page);
-		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_large(pmd) || !pmd_present(pmd))) {
-			/*
-			 * NUMA hinting faults need to be handled in the GUP
-			 * slowpath for accounting purposes and so that they
-			 * can be serialised against THP migration.
-			 */
-			if (pmd_protnone(pmd))
-				return 0;
-			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 noinline int gup_huge_pud(pud_t pud, unsigned long addr,
-		unsigned long end, int write, struct page **pages, int *nr)
-{
-	struct page *head, *page;
-	int refs;
-
-	if (!pte_allows_gup(pud_val(pud), write))
-		return 0;
-
-	VM_BUG_ON(!pfn_valid(pud_pfn(pud)));
-	if (pud_devmap(pud))
-		return __gup_device_huge_pud(pud, addr, end, pages, nr);
-
-	/* hugepages are never "special" */
-	VM_BUG_ON(pud_flags(pud) & _PAGE_SPECIAL);
-
-	refs = 0;
-	head = pud_page(pud);
-	page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
-	do {
-		VM_BUG_ON_PAGE(compound_head(page) != head, page);
-		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(p4d_t p4d, unsigned long addr, unsigned long end,
-			int write, struct page **pages, int *nr)
-{
-	unsigned long next;
-	pud_t *pudp;
-
-	pudp = pud_offset(&p4d, addr);
-	do {
-		pud_t pud = *pudp;
-
-		next = pud_addr_end(addr, end);
-		if (pud_none(pud))
-			return 0;
-		if (unlikely(pud_large(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;
-}
-
-static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
-			int write, struct page **pages, int *nr)
-{
-	unsigned long next;
-	p4d_t *p4dp;
-
-	p4dp = p4d_offset(&pgd, addr);
-	do {
-		p4d_t p4d = *p4dp;
-
-		next = p4d_addr_end(addr, end);
-		if (p4d_none(p4d))
-			return 0;
-		BUILD_BUG_ON(p4d_large(p4d));
-		if (!gup_pud_range(p4d, addr, next, write, pages, nr))
-			return 0;
-	} while (p4dp++, 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.
- */
-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 on x86.
-	 *
-	 * So long as we atomically load page table pointers versus teardown
-	 * (which we do on x86, with the above PAE exception), we can follow the
-	 * address down to the 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_p4d_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 nr = 0;
-
-	start &= PAGE_MASK;
-	addr = start;
-	len = (unsigned long) nr_pages << PAGE_SHIFT;
-
-	end = start + len;
-	if (end < start)
-		goto slow_irqon;
-
-#ifdef CONFIG_X86_64
-	if (end >> __VIRTUAL_MASK_SHIFT)
-		goto slow_irqon;
-#endif
-
-	/*
-	 * 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 on x86.
-	 *
-	 * So long as we atomically load page table pointers versus teardown
-	 * (which we do on x86, with the above PAE exception), we can follow the
-	 * address down to the the page and take a ref on it.
-	 */
-	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;
-		if (!gup_p4d_range(pgd, addr, next, write, pages, &nr))
-			goto slow;
-	} while (pgdp++, addr = next, addr != end);
-	local_irq_enable();
-
-	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
-	return nr;
-
-	{
-		int ret;
-
-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;
-	}
-}