[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>
This commit is contained in:
Martin Schwidefsky 2010-10-25 16:10:11 +02:00 committed by Martin Schwidefsky
parent 87799ebab7
commit 80217147a3
9 changed files with 395 additions and 28 deletions

View file

@ -101,6 +101,7 @@ config S390
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

View file

@ -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 @@ static inline void pmd_populate(struct mm_struct *mm,
#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 */

View file

@ -316,6 +316,7 @@ extern unsigned long VMALLOC_START;
/* 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 */

View file

@ -64,10 +64,9 @@ static inline void tlb_flush_mmu(struct mmu_gather *tlb,
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 @@ static inline void tlb_finish_mmu(struct mmu_gather *tlb,
{
tlb_flush_mmu(tlb, start, end);
rcu_table_freelist_finish();
/* keep the page table cache within bounds */
check_pgt_cache();
@ -103,7 +104,7 @@ static inline void pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte,
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 @@ static inline void pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd,
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 @@ static inline void pud_free_tlb(struct mmu_gather *tlb, pud_t *pud,
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
}

View file

@ -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

225
arch/s390/mm/gup.c Normal file
View file

@ -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;
}
}

View file

@ -68,7 +68,7 @@ void arch_release_hugepage(struct page *page)
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;
}

View file

@ -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;

View file

@ -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 @@ unsigned long *crst_table_alloc(struct mm_struct *mm, int noexec)
}
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 @@ int crst_table_upgrade(struct mm_struct *mm, unsigned long limit)
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 @@ int crst_table_upgrade(struct mm_struct *mm, unsigned long limit)
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 *page_table_alloc(struct mm_struct *mm)
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 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
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 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
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 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
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 @@ void page_table_free(struct mm_struct *mm, unsigned long *table)
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 @@ void page_table_free(struct mm_struct *mm, unsigned long *table)
} 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 @@ void disable_noexec(struct mm_struct *mm, struct task_struct *tsk)
/* "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);
}