[S390] lockless get_user_pages_fast()
Implement get_user_pages_fast without locking in the fastpath on s390.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 75976a1..7afc173 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -101,6 +101,7 @@
select HAVE_KERNEL_BZIP2
select HAVE_KERNEL_LZMA
select HAVE_KERNEL_LZO
+ select HAVE_GET_USER_PAGES_FAST
select ARCH_INLINE_SPIN_TRYLOCK
select ARCH_INLINE_SPIN_TRYLOCK_BH
select ARCH_INLINE_SPIN_LOCK
diff --git a/arch/s390/include/asm/pgalloc.h b/arch/s390/include/asm/pgalloc.h
index 68940d0..082eb4e 100644
--- a/arch/s390/include/asm/pgalloc.h
+++ b/arch/s390/include/asm/pgalloc.h
@@ -21,9 +21,11 @@
unsigned long *crst_table_alloc(struct mm_struct *, int);
void crst_table_free(struct mm_struct *, unsigned long *);
+void crst_table_free_rcu(struct mm_struct *, unsigned long *);
unsigned long *page_table_alloc(struct mm_struct *);
void page_table_free(struct mm_struct *, unsigned long *);
+void page_table_free_rcu(struct mm_struct *, unsigned long *);
void disable_noexec(struct mm_struct *, struct task_struct *);
static inline void clear_table(unsigned long *s, unsigned long val, size_t n)
@@ -176,4 +178,6 @@
#define pte_free_kernel(mm, pte) page_table_free(mm, (unsigned long *) pte)
#define pte_free(mm, pte) page_table_free(mm, (unsigned long *) pte)
+extern void rcu_table_freelist_finish(void);
+
#endif /* _S390_PGALLOC_H */
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 22a2945..785229a 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -316,6 +316,7 @@
/* Bits in the segment table entry */
#define _SEGMENT_ENTRY_ORIGIN 0x7fffffc0UL /* page table origin */
+#define _SEGMENT_ENTRY_RO 0x200 /* page protection bit */
#define _SEGMENT_ENTRY_INV 0x20 /* invalid segment table entry */
#define _SEGMENT_ENTRY_COMMON 0x10 /* common segment bit */
#define _SEGMENT_ENTRY_PTL 0x0f /* page table length */
diff --git a/arch/s390/include/asm/tlb.h b/arch/s390/include/asm/tlb.h
index fd1c00d..f1f644f 100644
--- a/arch/s390/include/asm/tlb.h
+++ b/arch/s390/include/asm/tlb.h
@@ -64,10 +64,9 @@
if (!tlb->fullmm && (tlb->nr_ptes > 0 || tlb->nr_pxds < TLB_NR_PTRS))
__tlb_flush_mm(tlb->mm);
while (tlb->nr_ptes > 0)
- pte_free(tlb->mm, tlb->array[--tlb->nr_ptes]);
+ page_table_free_rcu(tlb->mm, tlb->array[--tlb->nr_ptes]);
while (tlb->nr_pxds < TLB_NR_PTRS)
- /* pgd_free frees the pointer as region or segment table */
- pgd_free(tlb->mm, tlb->array[tlb->nr_pxds++]);
+ crst_table_free_rcu(tlb->mm, tlb->array[tlb->nr_pxds++]);
}
static inline void tlb_finish_mmu(struct mmu_gather *tlb,
@@ -75,6 +74,8 @@
{
tlb_flush_mmu(tlb, start, end);
+ rcu_table_freelist_finish();
+
/* keep the page table cache within bounds */
check_pgt_cache();
@@ -103,7 +104,7 @@
if (tlb->nr_ptes >= tlb->nr_pxds)
tlb_flush_mmu(tlb, 0, 0);
} else
- pte_free(tlb->mm, pte);
+ page_table_free(tlb->mm, (unsigned long *) pte);
}
/*
@@ -124,7 +125,7 @@
if (tlb->nr_ptes >= tlb->nr_pxds)
tlb_flush_mmu(tlb, 0, 0);
} else
- pmd_free(tlb->mm, pmd);
+ crst_table_free(tlb->mm, (unsigned long *) pmd);
#endif
}
@@ -146,7 +147,7 @@
if (tlb->nr_ptes >= tlb->nr_pxds)
tlb_flush_mmu(tlb, 0, 0);
} else
- pud_free(tlb->mm, pud);
+ crst_table_free(tlb->mm, (unsigned long *) pud);
#endif
}
diff --git a/arch/s390/mm/Makefile b/arch/s390/mm/Makefile
index eec0544..6fbc6f3 100644
--- a/arch/s390/mm/Makefile
+++ b/arch/s390/mm/Makefile
@@ -3,6 +3,6 @@
#
obj-y := init.o fault.o extmem.o mmap.o vmem.o pgtable.o maccess.o \
- page-states.o
+ page-states.o gup.o
obj-$(CONFIG_CMM) += cmm.o
obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
new file mode 100644
index 0000000..38e641c
--- /dev/null
+++ b/arch/s390/mm/gup.c
@@ -0,0 +1,225 @@
+/*
+ * Lockless get_user_pages_fast for s390
+ *
+ * Copyright IBM Corp. 2010
+ * Author(s): Martin Schwidefsky <schwidefsky@de.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 *pmdp, pmd_t pmd, unsigned long addr,
+ unsigned long end, int write, struct page **pages, int *nr)
+{
+ unsigned long mask, result;
+ pte_t *ptep, pte;
+ struct page *page;
+
+ result = write ? 0 : _PAGE_RO;
+ mask = result | _PAGE_INVALID | _PAGE_SPECIAL;
+
+ ptep = ((pte_t *) pmd_deref(pmd)) + pte_index(addr);
+ do {
+ pte = *ptep;
+ barrier();
+ if ((pte_val(pte) & mask) != result)
+ return 0;
+ VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
+ page = pte_page(pte);
+ if (!page_cache_get_speculative(page))
+ return 0;
+ if (unlikely(pte_val(pte) != pte_val(*ptep))) {
+ put_page(page);
+ return 0;
+ }
+ 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)
+{
+ unsigned long mask, result;
+ struct page *head, *page;
+ int refs;
+
+ result = write ? 0 : _SEGMENT_ENTRY_RO;
+ mask = result | _SEGMENT_ENTRY_INV;
+ if ((pmd_val(pmd) & mask) != result)
+ 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 1;
+}
+
+
+static inline int gup_pmd_range(pud_t *pudp, 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_t *) pudp;
+#ifdef CONFIG_64BIT
+ if ((pud_val(pud) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
+ pmdp = (pmd_t *) pud_deref(pud);
+ pmdp += pmd_index(addr);
+#endif
+ do {
+ pmd = *pmdp;
+ barrier();
+ next = pmd_addr_end(addr, end);
+ if (pmd_none(pmd))
+ return 0;
+ if (unlikely(pmd_huge(pmd))) {
+ if (!gup_huge_pmd(pmdp, pmd, addr, next,
+ write, pages, nr))
+ return 0;
+ } else if (!gup_pte_range(pmdp, pmd, addr, next,
+ write, pages, nr))
+ return 0;
+ } while (pmdp++, addr = next, addr != end);
+
+ return 1;
+}
+
+static inline int gup_pud_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr,
+ unsigned long end, int write, struct page **pages, int *nr)
+{
+ unsigned long next;
+ pud_t *pudp, pud;
+
+ pudp = (pud_t *) pgdp;
+#ifdef CONFIG_64BIT
+ if ((pgd_val(pgd) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R2)
+ pudp = (pud_t *) pgd_deref(pgd);
+ pudp += pud_index(addr);
+#endif
+ do {
+ pud = *pudp;
+ barrier();
+ next = pud_addr_end(addr, end);
+ if (pud_none(pud))
+ return 0;
+ if (!gup_pmd_range(pudp, pud, addr, next, write, pages, nr))
+ return 0;
+ } while (pudp++, addr = next, addr != end);
+
+ return 1;
+}
+
+/**
+ * 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, pgd;
+ 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() 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_disable();
+ pgdp = pgd_offset(mm, addr);
+ do {
+ pgd = *pgdp;
+ barrier();
+ next = pgd_addr_end(addr, end);
+ if (pgd_none(pgd))
+ goto slow;
+ if (!gup_pud_range(pgdp, 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;
+
+ down_read(&mm->mmap_sem);
+ ret = get_user_pages(current, mm, start,
+ (end - start) >> PAGE_SHIFT, write, 0, pages, NULL);
+ up_read(&mm->mmap_sem);
+
+ /* Have to be a bit careful with return values */
+ if (nr > 0) {
+ if (ret < 0)
+ ret = nr;
+ else
+ ret += nr;
+ }
+
+ return ret;
+ }
+}
diff --git a/arch/s390/mm/hugetlbpage.c b/arch/s390/mm/hugetlbpage.c
index f28c43d..639cd21 100644
--- a/arch/s390/mm/hugetlbpage.c
+++ b/arch/s390/mm/hugetlbpage.c
@@ -68,7 +68,7 @@
ptep = (pte_t *) page[1].index;
if (!ptep)
return;
- pte_free(&init_mm, ptep);
+ page_table_free(&init_mm, (unsigned long *) ptep);
page[1].index = 0;
}
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 0744fb3..852a3fe 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -38,8 +38,6 @@
#include <asm/tlbflush.h>
#include <asm/sections.h>
-DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
-
pgd_t swapper_pg_dir[PTRS_PER_PGD] __attribute__((__aligned__(PAGE_SIZE)));
unsigned long empty_zero_page, zero_page_mask;
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 8d99924..19338d2 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -15,6 +15,7 @@
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/quicklist.h>
+#include <linux/rcupdate.h>
#include <asm/system.h>
#include <asm/pgtable.h>
@@ -23,6 +24,67 @@
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
+struct rcu_table_freelist {
+ struct rcu_head rcu;
+ struct mm_struct *mm;
+ unsigned int pgt_index;
+ unsigned int crst_index;
+ unsigned long *table[0];
+};
+
+#define RCU_FREELIST_SIZE \
+ ((PAGE_SIZE - sizeof(struct rcu_table_freelist)) \
+ / sizeof(unsigned long))
+
+DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
+static DEFINE_PER_CPU(struct rcu_table_freelist *, rcu_table_freelist);
+
+static void __page_table_free(struct mm_struct *mm, unsigned long *table);
+static void __crst_table_free(struct mm_struct *mm, unsigned long *table);
+
+static struct rcu_table_freelist *rcu_table_freelist_get(struct mm_struct *mm)
+{
+ struct rcu_table_freelist **batchp = &__get_cpu_var(rcu_table_freelist);
+ struct rcu_table_freelist *batch = *batchp;
+
+ if (batch)
+ return batch;
+ batch = (struct rcu_table_freelist *) __get_free_page(GFP_ATOMIC);
+ if (batch) {
+ batch->mm = mm;
+ batch->pgt_index = 0;
+ batch->crst_index = RCU_FREELIST_SIZE;
+ *batchp = batch;
+ }
+ return batch;
+}
+
+static void rcu_table_freelist_callback(struct rcu_head *head)
+{
+ struct rcu_table_freelist *batch =
+ container_of(head, struct rcu_table_freelist, rcu);
+
+ while (batch->pgt_index > 0)
+ __page_table_free(batch->mm, batch->table[--batch->pgt_index]);
+ while (batch->crst_index < RCU_FREELIST_SIZE)
+ __crst_table_free(batch->mm, batch->table[batch->crst_index++]);
+ free_page((unsigned long) batch);
+}
+
+void rcu_table_freelist_finish(void)
+{
+ struct rcu_table_freelist *batch = __get_cpu_var(rcu_table_freelist);
+
+ if (!batch)
+ return;
+ call_rcu(&batch->rcu, rcu_table_freelist_callback);
+ __get_cpu_var(rcu_table_freelist) = NULL;
+}
+
+static void smp_sync(void *arg)
+{
+}
+
#ifndef CONFIG_64BIT
#define ALLOC_ORDER 1
#define TABLES_PER_PAGE 4
@@ -78,23 +140,53 @@
}
page->index = page_to_phys(shadow);
}
- spin_lock(&mm->context.list_lock);
+ spin_lock_bh(&mm->context.list_lock);
list_add(&page->lru, &mm->context.crst_list);
- spin_unlock(&mm->context.list_lock);
+ spin_unlock_bh(&mm->context.list_lock);
return (unsigned long *) page_to_phys(page);
}
+static void __crst_table_free(struct mm_struct *mm, unsigned long *table)
+{
+ unsigned long *shadow = get_shadow_table(table);
+
+ if (shadow)
+ free_pages((unsigned long) shadow, ALLOC_ORDER);
+ free_pages((unsigned long) table, ALLOC_ORDER);
+}
+
void crst_table_free(struct mm_struct *mm, unsigned long *table)
{
- unsigned long *shadow = get_shadow_table(table);
struct page *page = virt_to_page(table);
- spin_lock(&mm->context.list_lock);
+ spin_lock_bh(&mm->context.list_lock);
list_del(&page->lru);
- spin_unlock(&mm->context.list_lock);
- if (shadow)
- free_pages((unsigned long) shadow, ALLOC_ORDER);
- free_pages((unsigned long) table, ALLOC_ORDER);
+ spin_unlock_bh(&mm->context.list_lock);
+ __crst_table_free(mm, table);
+}
+
+void crst_table_free_rcu(struct mm_struct *mm, unsigned long *table)
+{
+ struct rcu_table_freelist *batch;
+ struct page *page = virt_to_page(table);
+
+ spin_lock_bh(&mm->context.list_lock);
+ list_del(&page->lru);
+ spin_unlock_bh(&mm->context.list_lock);
+ if (atomic_read(&mm->mm_users) < 2 &&
+ cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id()))) {
+ __crst_table_free(mm, table);
+ return;
+ }
+ batch = rcu_table_freelist_get(mm);
+ if (!batch) {
+ smp_call_function(smp_sync, NULL, 1);
+ __crst_table_free(mm, table);
+ return;
+ }
+ batch->table[--batch->crst_index] = table;
+ if (batch->pgt_index >= batch->crst_index)
+ rcu_table_freelist_finish();
}
#ifdef CONFIG_64BIT
@@ -108,7 +200,7 @@
table = crst_table_alloc(mm, mm->context.noexec);
if (!table)
return -ENOMEM;
- spin_lock(&mm->page_table_lock);
+ spin_lock_bh(&mm->page_table_lock);
if (mm->context.asce_limit < limit) {
pgd = (unsigned long *) mm->pgd;
if (mm->context.asce_limit <= (1UL << 31)) {
@@ -130,7 +222,7 @@
mm->task_size = mm->context.asce_limit;
table = NULL;
}
- spin_unlock(&mm->page_table_lock);
+ spin_unlock_bh(&mm->page_table_lock);
if (table)
crst_table_free(mm, table);
if (mm->context.asce_limit < limit)
@@ -182,7 +274,7 @@
unsigned long bits;
bits = (mm->context.noexec || mm->context.has_pgste) ? 3UL : 1UL;
- spin_lock(&mm->context.list_lock);
+ spin_lock_bh(&mm->context.list_lock);
page = NULL;
if (!list_empty(&mm->context.pgtable_list)) {
page = list_first_entry(&mm->context.pgtable_list,
@@ -191,7 +283,7 @@
page = NULL;
}
if (!page) {
- spin_unlock(&mm->context.list_lock);
+ spin_unlock_bh(&mm->context.list_lock);
page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
if (!page)
return NULL;
@@ -202,7 +294,7 @@
clear_table_pgstes(table);
else
clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
- spin_lock(&mm->context.list_lock);
+ spin_lock_bh(&mm->context.list_lock);
list_add(&page->lru, &mm->context.pgtable_list);
}
table = (unsigned long *) page_to_phys(page);
@@ -213,10 +305,25 @@
page->flags |= bits;
if ((page->flags & FRAG_MASK) == ((1UL << TABLES_PER_PAGE) - 1))
list_move_tail(&page->lru, &mm->context.pgtable_list);
- spin_unlock(&mm->context.list_lock);
+ spin_unlock_bh(&mm->context.list_lock);
return table;
}
+static void __page_table_free(struct mm_struct *mm, unsigned long *table)
+{
+ struct page *page;
+ unsigned long bits;
+
+ bits = ((unsigned long) table) & 15;
+ table = (unsigned long *)(((unsigned long) table) ^ bits);
+ page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
+ page->flags ^= bits;
+ if (!(page->flags & FRAG_MASK)) {
+ pgtable_page_dtor(page);
+ __free_page(page);
+ }
+}
+
void page_table_free(struct mm_struct *mm, unsigned long *table)
{
struct page *page;
@@ -225,7 +332,7 @@
bits = (mm->context.noexec || mm->context.has_pgste) ? 3UL : 1UL;
bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long);
page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
- spin_lock(&mm->context.list_lock);
+ spin_lock_bh(&mm->context.list_lock);
page->flags ^= bits;
if (page->flags & FRAG_MASK) {
/* Page now has some free pgtable fragments. */
@@ -234,18 +341,48 @@
} else
/* All fragments of the 4K page have been freed. */
list_del(&page->lru);
- spin_unlock(&mm->context.list_lock);
+ spin_unlock_bh(&mm->context.list_lock);
if (page) {
pgtable_page_dtor(page);
__free_page(page);
}
}
+void page_table_free_rcu(struct mm_struct *mm, unsigned long *table)
+{
+ struct rcu_table_freelist *batch;
+ struct page *page;
+ unsigned long bits;
+
+ if (atomic_read(&mm->mm_users) < 2 &&
+ cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id()))) {
+ page_table_free(mm, table);
+ return;
+ }
+ batch = rcu_table_freelist_get(mm);
+ if (!batch) {
+ smp_call_function(smp_sync, NULL, 1);
+ page_table_free(mm, table);
+ return;
+ }
+ bits = (mm->context.noexec || mm->context.has_pgste) ? 3UL : 1UL;
+ bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long);
+ page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
+ spin_lock_bh(&mm->context.list_lock);
+ /* Delayed freeing with rcu prevents reuse of pgtable fragments */
+ list_del_init(&page->lru);
+ spin_unlock_bh(&mm->context.list_lock);
+ table = (unsigned long *)(((unsigned long) table) | bits);
+ batch->table[batch->pgt_index++] = table;
+ if (batch->pgt_index >= batch->crst_index)
+ rcu_table_freelist_finish();
+}
+
void disable_noexec(struct mm_struct *mm, struct task_struct *tsk)
{
struct page *page;
- spin_lock(&mm->context.list_lock);
+ spin_lock_bh(&mm->context.list_lock);
/* Free shadow region and segment tables. */
list_for_each_entry(page, &mm->context.crst_list, lru)
if (page->index) {
@@ -255,7 +392,7 @@
/* "Free" second halves of page tables. */
list_for_each_entry(page, &mm->context.pgtable_list, lru)
page->flags &= ~SECOND_HALVES;
- spin_unlock(&mm->context.list_lock);
+ spin_unlock_bh(&mm->context.list_lock);
mm->context.noexec = 0;
update_mm(mm, tsk);
}