From: Christoph Hellwig <hch@xxxxxx> Subject: MIPS: use the generic get_user_pages_fast code The mips code is mostly equivalent to the generic one, minus various bugfixes and an arch override for gup_fast_permitted. Note that this defines ARCH_HAS_PTE_SPECIAL for mips as mips has pte_special and pte_mkspecial implemented and used in the existing gup code. They are no-op stubs, though which makes me a little unsure if this is really right thing to do. Note that this also adds back a missing cpu_has_dc_aliases check for __get_user_pages_fast, which the old code was only doing for get_user_pages_fast. This clearly looks like an oversight, as any condition that makes get_user_pages_fast unsafe also applies to __get_user_pages_fast. [hch@xxxxxx: MIPS: don't select ARCH_HAS_PTE_SPECIAL] Link: http://lkml.kernel.org/r/20190701151818.32227-3-hch@xxxxxx Link: http://lkml.kernel.org/r/20190625143715.1689-5-hch@xxxxxx Signed-off-by: Christoph Hellwig <hch@xxxxxx> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx> Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: David Miller <davem@xxxxxxxxxxxxx> Cc: James Hogan <jhogan@xxxxxxxxxx> Cc: Khalid Aziz <khalid.aziz@xxxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Nicholas Piggin <npiggin@xxxxxxxxx> Cc: Paul Burton <paul.burton@xxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Rich Felker <dalias@xxxxxxxx> Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/mips/Kconfig | 2 arch/mips/include/asm/pgtable.h | 3 arch/mips/mm/Makefile | 1 arch/mips/mm/gup.c | 303 ------------------------------ 4 files changed, 5 insertions(+), 304 deletions(-) --- a/arch/mips/include/asm/pgtable.h~mips-use-the-generic-get_user_pages_fast-code +++ a/arch/mips/include/asm/pgtable.h @@ -20,6 +20,7 @@ #include <asm/cmpxchg.h> #include <asm/io.h> #include <asm/pgtable-bits.h> +#include <asm/cpu-features.h> struct mm_struct; struct vm_area_struct; @@ -626,6 +627,8 @@ static inline pmd_t pmdp_huge_get_and_cl #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ +#define gup_fast_permitted(start, end) (!cpu_has_dc_aliases) + #include <asm-generic/pgtable.h> /* --- a/arch/mips/Kconfig~mips-use-the-generic-get_user_pages_fast-code +++ a/arch/mips/Kconfig @@ -34,6 +34,7 @@ config MIPS select GENERIC_SCHED_CLOCK if !CAVIUM_OCTEON_SOC select GENERIC_SMP_IDLE_THREAD select GENERIC_TIME_VSYSCALL + select GUP_GET_PTE_LOW_HIGH if CPU_MIPS32 && PHYS_ADDR_T_64BIT select HANDLE_DOMAIN_IRQ select HAVE_ARCH_COMPILER_H select HAVE_ARCH_JUMP_LABEL @@ -55,6 +56,7 @@ config MIPS select HAVE_FTRACE_MCOUNT_RECORD select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER + select HAVE_GENERIC_GUP select HAVE_IDE select HAVE_IOREMAP_PROT select HAVE_IRQ_EXIT_ON_IRQ_STACK --- a/arch/mips/mm/gup.c +++ /dev/null @@ -1,303 +0,0 @@ -// 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((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 - * @gup_flags: flags modifying pin behaviour - * @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, - unsigned int gup_flags, 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; - if (!gup_pud_range(pgd, addr, next, gup_flags & FOLL_WRITE, - 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, gup_flags); - - /* Have to be a bit careful with return values */ - if (nr > 0) { - if (ret < 0) - ret = nr; - else - ret += nr; - } - return ret; -} --- a/arch/mips/mm/Makefile~mips-use-the-generic-get_user_pages_fast-code +++ a/arch/mips/mm/Makefile @@ -7,7 +7,6 @@ obj-y += cache.o obj-y += context.o obj-y += extable.o obj-y += fault.o -obj-y += gup.o obj-y += init.o obj-y += mmap.o obj-y += page.o _
