[S390] use generic RCU page-table freeing code
Replace the s390 specific rcu page-table freeing code with the
generic variant. This requires to duplicate the definition for the
struct mmu_table_batch as s390 does not use the generic tlb flush
code.
While we are at it remove the restriction that page table fragments
can not be reused after a single fragment has been freed with rcu
and split out allocation and freeing of page tables with pgstes.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index b09763f..37a23c22 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -24,94 +24,12 @@
#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))
-
-static DEFINE_PER_CPU(struct rcu_table_freelist *, rcu_table_freelist);
-
-static void __page_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 **batchp = &get_cpu_var(rcu_table_freelist);
- struct rcu_table_freelist *batch = *batchp;
-
- if (!batch)
- goto out;
- call_rcu(&batch->rcu, rcu_table_freelist_callback);
- *batchp = NULL;
-out:
- put_cpu_var(rcu_table_freelist);
-}
-
-static void smp_sync(void *arg)
-{
-}
-
#ifndef CONFIG_64BIT
#define ALLOC_ORDER 1
-#define TABLES_PER_PAGE 4
-#define FRAG_MASK 15UL
-#define SECOND_HALVES 10UL
-
-void clear_table_pgstes(unsigned long *table)
-{
- clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/4);
- memset(table + 256, 0, PAGE_SIZE/4);
- clear_table(table + 512, _PAGE_TYPE_EMPTY, PAGE_SIZE/4);
- memset(table + 768, 0, PAGE_SIZE/4);
-}
-
+#define FRAG_MASK 0x0f
#else
#define ALLOC_ORDER 2
-#define TABLES_PER_PAGE 2
-#define FRAG_MASK 3UL
-#define SECOND_HALVES 2UL
-
-void clear_table_pgstes(unsigned long *table)
-{
- clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/2);
- memset(table + 256, 0, PAGE_SIZE/2);
-}
-
+#define FRAG_MASK 0x03
#endif
unsigned long VMALLOC_START = VMALLOC_END - VMALLOC_SIZE;
@@ -140,29 +58,6 @@
free_pages((unsigned long) table, ALLOC_ORDER);
}
-void crst_table_free_rcu(struct mm_struct *mm, unsigned long *table)
-{
- struct rcu_table_freelist *batch;
-
- preempt_disable();
- if (atomic_read(&mm->mm_users) < 2 &&
- cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id()))) {
- crst_table_free(mm, table);
- goto out;
- }
- batch = rcu_table_freelist_get(mm);
- if (!batch) {
- smp_call_function(smp_sync, NULL, 1);
- crst_table_free(mm, table);
- goto out;
- }
- batch->table[--batch->crst_index] = table;
- if (batch->pgt_index >= batch->crst_index)
- rcu_table_freelist_finish();
-out:
- preempt_enable();
-}
-
#ifdef CONFIG_64BIT
int crst_table_upgrade(struct mm_struct *mm, unsigned long limit)
{
@@ -238,124 +133,175 @@
}
#endif
+static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
+{
+ unsigned int old, new;
+
+ do {
+ old = atomic_read(v);
+ new = old ^ bits;
+ } while (atomic_cmpxchg(v, old, new) != old);
+ return new;
+}
+
/*
* page table entry allocation/free routines.
*/
+#ifdef CONFIG_PGSTE
+static inline unsigned long *page_table_alloc_pgste(struct mm_struct *mm)
+{
+ struct page *page;
+ unsigned long *table;
+
+ page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
+ if (!page)
+ return NULL;
+ pgtable_page_ctor(page);
+ atomic_set(&page->_mapcount, 3);
+ table = (unsigned long *) page_to_phys(page);
+ clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/2);
+ clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2);
+ return table;
+}
+
+static inline void page_table_free_pgste(unsigned long *table)
+{
+ struct page *page;
+
+ page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
+ pgtable_page_ctor(page);
+ atomic_set(&page->_mapcount, -1);
+ __free_page(page);
+}
+#endif
+
unsigned long *page_table_alloc(struct mm_struct *mm)
{
struct page *page;
unsigned long *table;
- unsigned long bits;
+ unsigned int mask, bit;
- bits = (mm->context.has_pgste) ? 3UL : 1UL;
+#ifdef CONFIG_PGSTE
+ if (mm_has_pgste(mm))
+ return page_table_alloc_pgste(mm);
+#endif
+ /* Allocate fragments of a 4K page as 1K/2K page table */
spin_lock_bh(&mm->context.list_lock);
- page = NULL;
+ mask = FRAG_MASK;
if (!list_empty(&mm->context.pgtable_list)) {
page = list_first_entry(&mm->context.pgtable_list,
struct page, lru);
- if ((page->flags & FRAG_MASK) == ((1UL << TABLES_PER_PAGE) - 1))
- page = NULL;
+ table = (unsigned long *) page_to_phys(page);
+ mask = atomic_read(&page->_mapcount);
+ mask = mask | (mask >> 4);
}
- if (!page) {
+ if ((mask & FRAG_MASK) == FRAG_MASK) {
spin_unlock_bh(&mm->context.list_lock);
page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
if (!page)
return NULL;
pgtable_page_ctor(page);
- page->flags &= ~FRAG_MASK;
+ atomic_set(&page->_mapcount, 1);
table = (unsigned long *) page_to_phys(page);
- if (mm->context.has_pgste)
- clear_table_pgstes(table);
- else
- clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
+ clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
spin_lock_bh(&mm->context.list_lock);
list_add(&page->lru, &mm->context.pgtable_list);
+ } else {
+ for (bit = 1; mask & bit; bit <<= 1)
+ table += PTRS_PER_PTE;
+ mask = atomic_xor_bits(&page->_mapcount, bit);
+ if ((mask & FRAG_MASK) == FRAG_MASK)
+ list_del(&page->lru);
}
- table = (unsigned long *) page_to_phys(page);
- while (page->flags & bits) {
- table += 256;
- bits <<= 1;
- }
- page->flags |= bits;
- if ((page->flags & FRAG_MASK) == ((1UL << TABLES_PER_PAGE) - 1))
- list_move_tail(&page->lru, &mm->context.pgtable_list);
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;
- unsigned long bits;
+ unsigned int bit, mask;
- bits = (mm->context.has_pgste) ? 3UL : 1UL;
- bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long);
+#ifdef CONFIG_PGSTE
+ if (mm_has_pgste(mm))
+ return page_table_free_pgste(table);
+#endif
+ /* Free 1K/2K page table fragment of a 4K page */
page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
+ bit = 1 << ((__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t)));
spin_lock_bh(&mm->context.list_lock);
- page->flags ^= bits;
- if (page->flags & FRAG_MASK) {
- /* Page now has some free pgtable fragments. */
- if (!list_empty(&page->lru))
- list_move(&page->lru, &mm->context.pgtable_list);
- page = NULL;
- } else
- /* All fragments of the 4K page have been freed. */
+ if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
list_del(&page->lru);
+ mask = atomic_xor_bits(&page->_mapcount, bit);
+ if (mask & FRAG_MASK)
+ list_add(&page->lru, &mm->context.pgtable_list);
spin_unlock_bh(&mm->context.list_lock);
- if (page) {
+ if (mask == 0) {
pgtable_page_dtor(page);
+ atomic_set(&page->_mapcount, -1);
__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;
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
- preempt_disable();
- if (atomic_read(&mm->mm_users) < 2 &&
- cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id()))) {
- page_table_free(mm, table);
- goto out;
+static void __page_table_free_rcu(void *table, unsigned bit)
+{
+ struct page *page;
+
+#ifdef CONFIG_PGSTE
+ if (bit == FRAG_MASK)
+ return page_table_free_pgste(table);
+#endif
+ /* Free 1K/2K page table fragment of a 4K page */
+ page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
+ if (atomic_xor_bits(&page->_mapcount, bit) == 0) {
+ pgtable_page_dtor(page);
+ atomic_set(&page->_mapcount, -1);
+ __free_page(page);
}
- batch = rcu_table_freelist_get(mm);
- if (!batch) {
- smp_call_function(smp_sync, NULL, 1);
- page_table_free(mm, table);
- goto out;
+}
+
+void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table)
+{
+ struct mm_struct *mm;
+ struct page *page;
+ unsigned int bit, mask;
+
+ mm = tlb->mm;
+#ifdef CONFIG_PGSTE
+ if (mm_has_pgste(mm)) {
+ table = (unsigned long *) (__pa(table) | FRAG_MASK);
+ tlb_remove_table(tlb, table);
+ return;
}
- bits = (mm->context.has_pgste) ? 3UL : 1UL;
- bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long);
+#endif
+ bit = 1 << ((__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t)));
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);
+ if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
+ list_del(&page->lru);
+ mask = atomic_xor_bits(&page->_mapcount, bit | (bit << 4));
+ if (mask & FRAG_MASK)
+ list_add_tail(&page->lru, &mm->context.pgtable_list);
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();
-out:
- preempt_enable();
+ table = (unsigned long *) (__pa(table) | (bit << 4));
+ tlb_remove_table(tlb, table);
}
+void __tlb_remove_table(void *_table)
+{
+ void *table = (void *)((unsigned long) _table & PAGE_MASK);
+ unsigned type = (unsigned long) _table & ~PAGE_MASK;
+
+ if (type)
+ __page_table_free_rcu(table, type);
+ else
+ free_pages((unsigned long) table, ALLOC_ORDER);
+}
+
+#endif
+
/*
* switch on pgstes for its userspace process (for kvm)
*/
@@ -369,7 +315,7 @@
return -EINVAL;
/* Do we have pgstes? if yes, we are done */
- if (tsk->mm->context.has_pgste)
+ if (mm_has_pgste(tsk->mm))
return 0;
/* lets check if we are allowed to replace the mm */