[PATCH 1/6] MIPS: use the generic get_user_pages_fast code

Christoph Hellwig
2019-05-25T13:32:26Z

The mips code is mostly equivalent to the generic one, minus various
bugfixes and one and a half arch overrides that this patch adds to
pgtable.h.

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.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
arch/mips/Kconfig | 2 +
arch/mips/include/asm/pgtable.h | 30 ++++
arch/mips/mm/Makefile | 1 -
arch/mips/mm/gup.c | 303 --------------------------------
4 files changed, 32 insertions(+), 304 deletions(-)
delete mode 100644 arch/mips/mm/gup.c

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 70d3200476bf..53a103cdc352 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -6,6 +6,7 @@ config MIPS
select ARCH_BINFMT_ELF_STATE if MIPS_FP_SUPPORT
select ARCH_CLOCKSOURCE_DATA
select ARCH_HAS_ELF_RANDOMIZE
+ select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAS_UBSAN_SANITIZE_ALL
select ARCH_SUPPORTS_UPROBES
@@ -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
diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index 4ccb465ef3f2..a6fd98563837 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/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;
@@ -651,4 +652,33 @@ pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
*/
#define pgtable_cache_init() do { } while (0)

+static inline bool gup_fast_permitted(unsigned long start, int nr_pages)
+{
+ unsigned long len = (unsigned long)nr_pages << PAGE_SHIFT;
+ unsigned long end = start + len;
+
+ return !cpu_has_dc_aliases && end >= start;
+}
+#define gup_fast_permitted gup_fast_permitted
+
+#if defined(CONFIG_PHYS_ADDR_T_64BIT) && defined(CONFIG_CPU_MIPS32)
+static inline pte_t gup_get_pte(pte_t *ptep)
+{
+ 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;
+}
+#define gup_get_pte gup_get_pte
+#endif
+
+static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
+
#endif /* _ASM_PGTABLE_H */
diff --git a/arch/mips/mm/Makefile b/arch/mips/mm/Makefile
index f34d7ff5eb60..1e8d335025d7 100644
--- a/arch/mips/mm/Makefile
+++ b/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
diff --git a/arch/mips/mm/gup.c b/arch/mips/mm/gup.c
deleted file mode 100644
index 4c2b4483683c..000000000000
--- 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;
-}
--
2.20.1