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>

5 files changed, 41 insertions, 29 deletions

diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
index bc0eadf9ed8e..2cf49624af99 100644
--- 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 081b2ad99d73..b941528cc49e 100644
--- 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 c837b79b455d..3ce3854b7a41 100644
--- 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 b5820bf47ec6..8b56423a8297 100644
--- 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 e8b5962ac12a..7be1f94f70a8 100644
--- 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);
 }