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Date: Wed, 22 May 2019 16:46:16 -0500
From: Justin Forbes <jmforbes@...uxtx.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 5.0 119/123] s390/mm: convert to the generic
get_user_pages_fast code
On Mon, May 20, 2019 at 7:30 AM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> From: Martin Schwidefsky <schwidefsky@...ibm.com>
>
> commit 1a42010cdc26bb7e5912984f3c91b8c6d55f089a upstream.
>
> Define the gup_fast_permitted to check against the asce_limit of the
> mm attached to the current task, then replace the s390 specific gup
> code with the generic implementation in mm/gup.c.
>
> Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
While this code seems to work fine upstream, when backported to 5.0 it
fails to build:
BUILDSTDERR: In file included from ./include/linux/mm.h:98,
BUILDSTDERR: from mm/gup.c:6:
BUILDSTDERR: mm/gup.c: In function '__get_user_pages_fast':
BUILDSTDERR: ./arch/s390/include/asm/pgtable.h:1277:28: error: too
many arguments to function 'gup_fast_permitted'
BUILDSTDERR: #define gup_fast_permitted gup_fast_permitted
BUILDSTDERR: ^~~~~~~~~~~~~~~~~~
BUILDSTDERR: mm/gup.c:1856:6: note: in expansion of macro 'gup_fast_permitted'
BUILDSTDERR: if (gup_fast_permitted(start, nr_pages, write)) {
It is missing upstream commit ad8cfb9c42ef83ecf4079bc7d77e6557648e952b
mm/gup: Remove the 'write' parameter from gup_fast_permitted()
Justin
>
> ---
> arch/s390/Kconfig | 1
> arch/s390/include/asm/pgtable.h | 12 +
> arch/s390/mm/Makefile | 2
> arch/s390/mm/gup.c | 291 ----------------------------------------
> 4 files changed, 14 insertions(+), 292 deletions(-)
>
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -148,6 +148,7 @@ config S390
> select HAVE_FUNCTION_TRACER
> select HAVE_FUTEX_CMPXCHG if FUTEX
> select HAVE_GCC_PLUGINS
> + select HAVE_GENERIC_GUP
> select HAVE_KERNEL_BZIP2
> select HAVE_KERNEL_GZIP
> select HAVE_KERNEL_LZ4
> --- a/arch/s390/include/asm/pgtable.h
> +++ b/arch/s390/include/asm/pgtable.h
> @@ -1264,6 +1264,18 @@ static inline pte_t *pte_offset(pmd_t *p
> #define pte_offset_map(pmd, address) pte_offset_kernel(pmd, address)
> #define pte_unmap(pte) do { } while (0)
>
> +static inline bool gup_fast_permitted(unsigned long start, int nr_pages)
> +{
> + unsigned long len, end;
> +
> + len = (unsigned long) nr_pages << PAGE_SHIFT;
> + end = start + len;
> + if (end < start)
> + return false;
> + return end <= current->mm->context.asce_limit;
> +}
> +#define gup_fast_permitted gup_fast_permitted
> +
> #define pfn_pte(pfn,pgprot) mk_pte_phys(__pa((pfn) << PAGE_SHIFT),(pgprot))
> #define pte_pfn(x) (pte_val(x) >> PAGE_SHIFT)
> #define pte_page(x) pfn_to_page(pte_pfn(x))
> --- a/arch/s390/mm/Makefile
> +++ b/arch/s390/mm/Makefile
> @@ -4,7 +4,7 @@
> #
>
> obj-y := init.o fault.o extmem.o mmap.o vmem.o maccess.o
> -obj-y += page-states.o gup.o pageattr.o pgtable.o pgalloc.o
> +obj-y += page-states.o pageattr.o pgtable.o pgalloc.o
>
> obj-$(CONFIG_CMM) += cmm.o
> obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
> --- a/arch/s390/mm/gup.c
> +++ /dev/null
> @@ -1,291 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -/*
> - * Lockless get_user_pages_fast for s390
> - *
> - * Copyright IBM Corp. 2010
> - * Author(s): Martin Schwidefsky <schwidefsky@...ibm.com>
> - */
> -#include <linux/sched.h>
> -#include <linux/mm.h>
> -#include <linux/hugetlb.h>
> -#include <linux/vmstat.h>
> -#include <linux/pagemap.h>
> -#include <linux/rwsem.h>
> -#include <asm/pgtable.h>
> -
> -/*
> - * The performance critical leaf functions are made noinline otherwise gcc
> - * inlines everything into a single function which results in too much
> - * register pressure.
> - */
> -static inline int gup_pte_range(pmd_t pmd, unsigned long addr,
> - unsigned long end, int write, struct page **pages, int *nr)
> -{
> - struct page *head, *page;
> - unsigned long mask;
> - pte_t *ptep, pte;
> -
> - mask = (write ? _PAGE_PROTECT : 0) | _PAGE_INVALID | _PAGE_SPECIAL;
> -
> - ptep = pte_offset_map(&pmd, addr);
> - do {
> - pte = *ptep;
> - barrier();
> - /* Similar to the PMD case, NUMA hinting must take slow path */
> - if (pte_protnone(pte))
> - return 0;
> - if ((pte_val(pte) & mask) != 0)
> - return 0;
> - VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
> - page = pte_page(pte);
> - head = compound_head(page);
> - if (!page_cache_get_speculative(head))
> - return 0;
> - if (unlikely(pte_val(pte) != pte_val(*ptep))) {
> - put_page(head);
> - return 0;
> - }
> - VM_BUG_ON_PAGE(compound_head(page) != head, page);
> - pages[*nr] = page;
> - (*nr)++;
> -
> - } while (ptep++, addr += PAGE_SIZE, addr != end);
> -
> - return 1;
> -}
> -
> -static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
> - unsigned long end, int write, struct page **pages, int *nr)
> -{
> - struct page *head, *page;
> - unsigned long mask;
> - int refs;
> -
> - mask = (write ? _SEGMENT_ENTRY_PROTECT : 0) | _SEGMENT_ENTRY_INVALID;
> - if ((pmd_val(pmd) & mask) != 0)
> - return 0;
> - VM_BUG_ON(!pfn_valid(pmd_val(pmd) >> PAGE_SHIFT));
> -
> - refs = 0;
> - head = pmd_page(pmd);
> - 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);
> -
> - if (!page_cache_add_speculative(head, refs)) {
> - *nr -= refs;
> - return 0;
> - }
> -
> - if (unlikely(pmd_val(pmd) != pmd_val(*pmdp))) {
> - *nr -= refs;
> - while (refs--)
> - put_page(head);
> - return 0;
> - }
> -
> - return 1;
> -}
> -
> -
> -static inline 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, pmd;
> -
> - pmdp = pmd_offset(&pud, addr);
> - do {
> - pmd = *pmdp;
> - barrier();
> - next = pmd_addr_end(addr, end);
> - if (pmd_none(pmd))
> - return 0;
> - if (unlikely(pmd_large(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(pmdp, 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 *pudp, pud_t pud, unsigned long addr,
> - unsigned long end, int write, struct page **pages, int *nr)
> -{
> - struct page *head, *page;
> - unsigned long mask;
> - int refs;
> -
> - mask = (write ? _REGION_ENTRY_PROTECT : 0) | _REGION_ENTRY_INVALID;
> - if ((pud_val(pud) & mask) != 0)
> - return 0;
> - VM_BUG_ON(!pfn_valid(pud_pfn(pud)));
> -
> - 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);
> -
> - if (!page_cache_add_speculative(head, refs)) {
> - *nr -= refs;
> - return 0;
> - }
> -
> - if (unlikely(pud_val(pud) != pud_val(*pudp))) {
> - *nr -= refs;
> - while (refs--)
> - put_page(head);
> - return 0;
> - }
> -
> - return 1;
> -}
> -
> -static inline 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, pud;
> -
> - pudp = pud_offset(&p4d, addr);
> - do {
> - pud = *pudp;
> - barrier();
> - next = pud_addr_end(addr, end);
> - if (pud_none(pud))
> - return 0;
> - if (unlikely(pud_large(pud))) {
> - if (!gup_huge_pud(pudp, 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 inline 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, p4d;
> -
> - p4dp = p4d_offset(&pgd, addr);
> - do {
> - p4d = *p4dp;
> - barrier();
> - next = p4d_addr_end(addr, end);
> - if (p4d_none(p4d))
> - return 0;
> - 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.
> - * 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, flags;
> - pgd_t *pgdp, pgd;
> - int nr = 0;
> -
> - start &= PAGE_MASK;
> - addr = start;
> - len = (unsigned long) nr_pages << PAGE_SHIFT;
> - end = start + len;
> - if ((end <= start) || (end > mm->context.asce_limit))
> - return 0;
> - /*
> - * local_irq_save() doesn't prevent pagetable teardown, but does
> - * prevent the pagetables from being freed on s390.
> - *
> - * So long as we atomically load page table pointers versus teardown,
> - * 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 = *pgdp;
> - barrier();
> - 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)
> -{
> - int nr, ret;
> -
> - might_sleep();
> - start &= PAGE_MASK;
> - nr = __get_user_pages_fast(start, nr_pages, write, pages);
> - if (nr == nr_pages)
> - return nr;
> -
> - /* Try to get the remaining pages with get_user_pages */
> - start += nr << PAGE_SHIFT;
> - pages += nr;
> - ret = get_user_pages_unlocked(start, nr_pages - nr, pages,
> - write ? FOLL_WRITE : 0);
> - /* Have to be a bit careful with return values */
> - if (nr > 0)
> - ret = (ret < 0) ? nr : ret + nr;
> - return ret;
> -}
>
>
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