[PATCH 3/6] sh: use the generic get_user_pages_fast code

Christoph Hellwig
2019-05-25T13:32:43Z

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

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
arch/sh/Kconfig | 1 +
arch/sh/include/asm/pgtable.h | 85 +++++++++++
arch/sh/mm/Makefile | 2 +-
arch/sh/mm/gup.c | 277 ----------------------------------
4 files changed, 87 insertions(+), 278 deletions(-)
delete mode 100644 arch/sh/mm/gup.c

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index b77f512bb176..2fd8c12ca128 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -14,6 +14,7 @@ config SUPERH
select HAVE_ARCH_TRACEHOOK
select HAVE_PERF_EVENTS
select HAVE_DEBUG_BUGVERBOSE
+ select HAVE_GENERIC_GUP
select ARCH_HAVE_CUSTOM_GPIO_H
select ARCH_HAVE_NMI_SAFE_CMPXCHG if (GUSA_RB || CPU_SH4A)
select ARCH_HAS_GCOV_PROFILE_ALL
diff --git a/arch/sh/include/asm/pgtable.h b/arch/sh/include/asm/pgtable.h
index 3587103afe59..d3c177144f90 100644
--- a/arch/sh/include/asm/pgtable.h
+++ b/arch/sh/include/asm/pgtable.h
@@ -149,6 +149,91 @@ extern void paging_init(void);
extern void page_table_range_init(unsigned long start, unsigned long end,
pgd_t *pgd);

+static inline bool __pte_access_permitted(pte_t pte, u64 prot)
+{
+ return (pte_val(pte) & (prot | _PAGE_SPECIAL)) == prot;
+}
+
+#ifdef CONFIG_X2TLB
+static inline pte_t gup_get_pte(pte_t *ptep)
+{
+ /*
+ * 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 with 64-bit PTEs. 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;
+}
+#define gup_get_pte gup_get_pte
+
+static inline bool pte_access_permitted(pte_t pte, bool write)
+{
+ u64 prot = _PAGE_PRESENT;
+
+ prot |= _PAGE_EXT(_PAGE_EXT_KERN_READ | _PAGE_EXT_USER_READ);
+ if (write)
+ prot |= _PAGE_EXT(_PAGE_EXT_KERN_WRITE | _PAGE_EXT_USER_WRITE);
+ return __pte_access_permitted(pte, prot);
+}
+#elif defined(CONFIG_SUPERH64)
+static inline bool pte_access_permitted(pte_t pte, bool write)
+{
+ u64 prot = _PAGE_PRESENT | _PAGE_USER | _PAGE_READ;
+
+ if (write)
+ prot |= _PAGE_WRITE;
+ return __pte_access_permitted(pte, prot);
+}
+#else
+static inline bool pte_access_permitted(pte_t pte, bool write)
+{
+ u64 prot = _PAGE_PRESENT | _PAGE_USER;
+
+ if (write)
+ prot |= _PAGE_RW;
+ return __pte_access_permitted(pte, prot);
+#endif
+
+#define pte_access_permitted pte_access_permitted
+
/* arch/sh/mm/mmap.c */
#define HAVE_ARCH_UNMAPPED_AREA
#define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
diff --git a/arch/sh/mm/Makefile b/arch/sh/mm/Makefile
index fbe5e79751b3..5051b38fd5b6 100644
--- a/arch/sh/mm/Makefile
+++ b/arch/sh/mm/Makefile
@@ -17,7 +17,7 @@ cacheops-$(CONFIG_CPU_SHX3) += cache-shx3.o
obj-y += $(cacheops-y)

mmu-y := nommu.o extable_32.o
-mmu-$(CONFIG_MMU) := extable_$(BITS).o fault.o gup.o ioremap.o kmap.o \
+mmu-$(CONFIG_MMU) := extable_$(BITS).o fault.o ioremap.o kmap.o \
pgtable.o tlbex_$(BITS).o tlbflush_$(BITS).o

obj-y += $(mmu-y)
diff --git a/arch/sh/mm/gup.c b/arch/sh/mm/gup.c
deleted file mode 100644
index 277c882f7489..000000000000
--- a/arch/sh/mm/gup.c
+++ /dev/null
@@ -1,277 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Lockless get_user_pages_fast for SuperH
- *
- * Copyright (C) 2009 - 2010 Paul Mundt
- *
- * Cloned from the x86 and PowerPC versions, by:
- *
- * 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 <asm/pgtable.h>
-
-static inline pte_t gup_get_pte(pte_t *ptep)
-{
-#ifndef CONFIG_X2TLB
- 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 with 64-bit PTEs. 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
-}
-
-/*
- * 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)
-{
- u64 mask, result;
- pte_t *ptep;
-
-#ifdef CONFIG_X2TLB
- result = _PAGE_PRESENT | _PAGE_EXT(_PAGE_EXT_KERN_READ | _PAGE_EXT_USER_READ);
- if (write)
- result |= _PAGE_EXT(_PAGE_EXT_KERN_WRITE | _PAGE_EXT_USER_WRITE);
-#elif defined(CONFIG_SUPERH64)
- result = _PAGE_PRESENT | _PAGE_USER | _PAGE_READ;
- if (write)
- result |= _PAGE_WRITE;
-#else
- result = _PAGE_PRESENT | _PAGE_USER;
- if (write)
- result |= _PAGE_RW;
-#endif
-
- mask = result | _PAGE_SPECIAL;
-
- ptep = pte_offset_map(&pmd, addr);
- do {
- pte_t pte = gup_get_pte(ptep);
- struct page *page;
-
- if ((pte_val(pte) & mask) != result) {
- pte_unmap(ptep);
- return 0;
- }
- VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
- page = pte_page(pte);
- get_page(page);
- __flush_anon_page(page, addr);
- flush_dcache_page(page);
- pages[*nr] = page;
- (*nr)++;
-
- } while (ptep++, addr += PAGE_SIZE, addr != end);
- pte_unmap(ptep - 1);
-
- 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 (!gup_pte_range(pmd, addr, next, write, pages, nr))
- return 0;
- } while (pmdp++, addr = next, addr != end);
-
- 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 (!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;
-
- /*
- * This doesn't prevent pagetable teardown, but does prevent
- * the pagetables and pages from being freed.
- */
- 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 nr = 0;
-
- start &= PAGE_MASK;
- addr = start;
- len = (unsigned long) nr_pages << PAGE_SHIFT;
-
- end = start + len;
- if (end < start)
- goto slow_irqon;
-
- 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;
-
- {
- 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,
- 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