s390/mm: use RCU for gmap notifier list and the per-mm gmap list

The gmap notifier list and the gmap list in the mm_struct change rarely.
Use RCU to optimize the reader of these lists.

Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
index bc0eadf..2cf4962 100644 (file)
--- a/arch/s390/include/asm/gmap.h
+++ b/arch/s390/include/asm/gmap.h
@@ -39,6 +39,7 @@ struct gmap {
  */
 struct gmap_notifier {
        struct list_head list;
+       struct rcu_head rcu;
        void (*notifier_call)(struct gmap *gmap, unsigned long start,
                              unsigned long end);
 };

diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
index 081b2ad..b941528 100644 (file)
--- a/arch/s390/include/asm/mmu.h
+++ b/arch/s390/include/asm/mmu.h
@@ -8,8 +8,9 @@ typedef struct {
        cpumask_t cpu_attach_mask;
        atomic_t attach_count;
        unsigned int flush_mm;
-       spinlock_t list_lock;
+       spinlock_t pgtable_lock;
        struct list_head pgtable_list;
+       spinlock_t gmap_lock;
        struct list_head gmap_list;
        unsigned long asce;
        unsigned long asce_limit;
@@ -22,9 +23,11 @@ typedef struct {
        unsigned int use_skey:1;
 } mm_context_t;
 
-#define INIT_MM_CONTEXT(name)                                                \
-       .context.list_lock    = __SPIN_LOCK_UNLOCKED(name.context.list_lock), \
-       .context.pgtable_list = LIST_HEAD_INIT(name.context.pgtable_list),    \
+#define INIT_MM_CONTEXT(name)                                             \
+       .context.pgtable_lock =                                            \
+                       __SPIN_LOCK_UNLOCKED(name.context.pgtable_lock),   \
+       .context.pgtable_list = LIST_HEAD_INIT(name.context.pgtable_list), \
+       .context.gmap_lock = __SPIN_LOCK_UNLOCKED(name.context.gmap_lock), \
        .context.gmap_list = LIST_HEAD_INIT(name.context.gmap_list),
 
 static inline int tprot(unsigned long addr)

diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index c837b79..3ce3854 100644 (file)
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -15,8 +15,9 @@
 static inline int init_new_context(struct task_struct *tsk,
                                   struct mm_struct *mm)
 {
-       spin_lock_init(&mm->context.list_lock);
+       spin_lock_init(&mm->context.pgtable_lock);
        INIT_LIST_HEAD(&mm->context.pgtable_list);
+       spin_lock_init(&mm->context.gmap_lock);
        INIT_LIST_HEAD(&mm->context.gmap_list);
        cpumask_clear(&mm->context.cpu_attach_mask);
        atomic_set(&mm->context.attach_count, 0);

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index b5820bf..8b56423 100644 (file)
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -70,9 +70,9 @@ struct gmap *gmap_alloc(struct mm_struct *mm, unsigned long limit)
        gmap->asce = atype | _ASCE_TABLE_LENGTH |
                _ASCE_USER_BITS | __pa(table);
        gmap->asce_end = limit;
-       down_write(&mm->mmap_sem);
-       list_add(&gmap->list, &mm->context.gmap_list);
-       up_write(&mm->mmap_sem);
+       spin_lock(&mm->context.gmap_lock);
+       list_add_rcu(&gmap->list, &mm->context.gmap_list);
+       spin_unlock(&mm->context.gmap_lock);
        return gmap;
 
 out_free:
@@ -128,14 +128,16 @@ void gmap_free(struct gmap *gmap)
        else
                __tlb_flush_global();
 
+       spin_lock(&gmap->mm->context.gmap_lock);
+       list_del_rcu(&gmap->list);
+       spin_unlock(&gmap->mm->context.gmap_lock);
+       synchronize_rcu();
+
        /* Free all segment & region tables. */
        list_for_each_entry_safe(page, next, &gmap->crst_list, lru)
                __free_pages(page, 2);
        gmap_radix_tree_free(&gmap->guest_to_host);
        gmap_radix_tree_free(&gmap->host_to_guest);
-       down_write(&gmap->mm->mmap_sem);
-       list_del(&gmap->list);
-       up_write(&gmap->mm->mmap_sem);
        kfree(gmap);
 }
 EXPORT_SYMBOL_GPL(gmap_free);
@@ -369,11 +371,13 @@ void gmap_unlink(struct mm_struct *mm, unsigned long *table,
        struct gmap *gmap;
        int flush;
 
-       list_for_each_entry(gmap, &mm->context.gmap_list, list) {
+       rcu_read_lock();
+       list_for_each_entry_rcu(gmap, &mm->context.gmap_list, list) {
                flush = __gmap_unlink_by_vmaddr(gmap, vmaddr);
                if (flush)
                        gmap_flush_tlb(gmap);
        }
+       rcu_read_unlock();
 }
 
 /**
@@ -555,7 +559,7 @@ static DEFINE_SPINLOCK(gmap_notifier_lock);
 void gmap_register_ipte_notifier(struct gmap_notifier *nb)
 {
        spin_lock(&gmap_notifier_lock);
-       list_add(&nb->list, &gmap_notifier_list);
+       list_add_rcu(&nb->list, &gmap_notifier_list);
        spin_unlock(&gmap_notifier_lock);
 }
 EXPORT_SYMBOL_GPL(gmap_register_ipte_notifier);
@@ -567,8 +571,9 @@ EXPORT_SYMBOL_GPL(gmap_register_ipte_notifier);
 void gmap_unregister_ipte_notifier(struct gmap_notifier *nb)
 {
        spin_lock(&gmap_notifier_lock);
-       list_del_init(&nb->list);
+       list_del_rcu(&nb->list);
        spin_unlock(&gmap_notifier_lock);
+       synchronize_rcu();
 }
 EXPORT_SYMBOL_GPL(gmap_unregister_ipte_notifier);
 
@@ -662,16 +667,18 @@ void ptep_notify(struct mm_struct *mm, unsigned long vmaddr, pte_t *pte)
 
        offset = ((unsigned long) pte) & (255 * sizeof(pte_t));
        offset = offset * (4096 / sizeof(pte_t));
-       spin_lock(&gmap_notifier_lock);
-       list_for_each_entry(gmap, &mm->context.gmap_list, list) {
+       rcu_read_lock();
+       list_for_each_entry_rcu(gmap, &mm->context.gmap_list, list) {
+               spin_lock(&gmap->guest_table_lock);
                table = radix_tree_lookup(&gmap->host_to_guest,
                                          vmaddr >> PMD_SHIFT);
-               if (!table)
-                       continue;
-               gaddr = __gmap_segment_gaddr(table) + offset;
-               gmap_call_notifier(gmap, gaddr, gaddr + PAGE_SIZE - 1);
+               if (table)
+                       gaddr = __gmap_segment_gaddr(table) + offset;
+               spin_unlock(&gmap->guest_table_lock);
+               if (table)
+                       gmap_call_notifier(gmap, gaddr, gaddr + PAGE_SIZE - 1);
        }
-       spin_unlock(&gmap_notifier_lock);
+       rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(ptep_notify);
 

diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c
index e8b5962..7be1f94 100644 (file)
--- a/arch/s390/mm/pgalloc.c
+++ b/arch/s390/mm/pgalloc.c
@@ -149,7 +149,7 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
        /* Try to get a fragment of a 4K page as a 2K page table */
        if (!mm_alloc_pgste(mm)) {
                table = NULL;
-               spin_lock_bh(&mm->context.list_lock);
+               spin_lock_bh(&mm->context.pgtable_lock);
                if (!list_empty(&mm->context.pgtable_list)) {
                        page = list_first_entry(&mm->context.pgtable_list,
                                                struct page, lru);
@@ -164,7 +164,7 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
                                list_del(&page->lru);
                        }
                }
-               spin_unlock_bh(&mm->context.list_lock);
+               spin_unlock_bh(&mm->context.pgtable_lock);
                if (table)
                        return table;
        }
@@ -187,9 +187,9 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
                /* Return the first 2K fragment of the page */
                atomic_set(&page->_mapcount, 1);
                clear_table(table, _PAGE_INVALID, PAGE_SIZE);
-               spin_lock_bh(&mm->context.list_lock);
+               spin_lock_bh(&mm->context.pgtable_lock);
                list_add(&page->lru, &mm->context.pgtable_list);
-               spin_unlock_bh(&mm->context.list_lock);
+               spin_unlock_bh(&mm->context.pgtable_lock);
        }
        return table;
 }
@@ -203,13 +203,13 @@ void page_table_free(struct mm_struct *mm, unsigned long *table)
        if (!mm_alloc_pgste(mm)) {
                /* Free 2K page table fragment of a 4K page */
                bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
-               spin_lock_bh(&mm->context.list_lock);
+               spin_lock_bh(&mm->context.pgtable_lock);
                mask = atomic_xor_bits(&page->_mapcount, 1U << bit);
                if (mask & 3)
                        list_add(&page->lru, &mm->context.pgtable_list);
                else
                        list_del(&page->lru);
-               spin_unlock_bh(&mm->context.list_lock);
+               spin_unlock_bh(&mm->context.pgtable_lock);
                if (mask != 0)
                        return;
        }
@@ -235,13 +235,13 @@ void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
                return;
        }
        bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
-       spin_lock_bh(&mm->context.list_lock);
+       spin_lock_bh(&mm->context.pgtable_lock);
        mask = atomic_xor_bits(&page->_mapcount, 0x11U << bit);
        if (mask & 3)
                list_add_tail(&page->lru, &mm->context.pgtable_list);
        else
                list_del(&page->lru);
-       spin_unlock_bh(&mm->context.list_lock);
+       spin_unlock_bh(&mm->context.pgtable_lock);
        table = (unsigned long *) (__pa(table) | (1U << bit));
        tlb_remove_table(tlb, table);
 }