ACPI: Do not use krefs under a mutex in osl.c

The reference counting of ACPI iomaps is carried out entirely under
acpi_ioremap_lock, so it is sufficient to use simple counters instead
of krefs for this purpose.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 16 insertions, 20 deletions

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 445f205752a2..5389f9f2e2ff 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -105,7 +105,7 @@ struct acpi_ioremap {
         void __iomem *virt;
         acpi_physical_address phys;
         acpi_size size;
-        struct kref ref;
+        unsigned long refcount;
 };
 
 static LIST_HEAD(acpi_ioremaps);
@@ -319,7 +319,7 @@ acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
         /* Check if there's a suitable mapping already. */
         map = acpi_map_lookup(phys, size);
         if (map) {
-                kref_get(&map->ref);
+                map->refcount++;
                 goto out;
         }
 
@@ -342,7 +342,7 @@ acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
         map->virt = virt;
         map->phys = pg_off;
         map->size = pg_sz;
-        kref_init(&map->ref);
+        map->refcount = 1;
 
         list_add_tail_rcu(&map->list, &acpi_ioremaps);
 
@@ -352,25 +352,24 @@ acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
 }
 EXPORT_SYMBOL_GPL(acpi_os_map_memory);
 
-static void acpi_kref_del_iomap(struct kref *ref)
+static void acpi_os_drop_map_ref(struct acpi_ioremap *map)
 {
-        struct acpi_ioremap *map;
-
-        map = container_of(ref, struct acpi_ioremap, ref);
-        list_del_rcu(&map->list);
+        if (!--map->refcount)
+                list_del_rcu(&map->list);
 }
 
-static void acpi_os_remove_map(struct acpi_ioremap *map)
+static void acpi_os_map_cleanup(struct acpi_ioremap *map)
 {
-        synchronize_rcu();
-        iounmap(map->virt);
-        kfree(map);
+        if (!map->refcount) {
+                synchronize_rcu();
+                iounmap(map->virt);
+                kfree(map);
+        }
 }
 
 void __ref acpi_os_unmap_memory(void __iomem *virt, acpi_size size)
 {
         struct acpi_ioremap *map;
-        int del;
 
         if (!acpi_gbl_permanent_mmap) {
                 __acpi_unmap_table(virt, size);
@@ -384,11 +383,10 @@ void __ref acpi_os_unmap_memory(void __iomem *virt, acpi_size size)
                 WARN(true, PREFIX "%s: bad address %p\n", __func__, virt);
                 return;
         }
-        del = kref_put(&map->ref, acpi_kref_del_iomap);
+        acpi_os_drop_map_ref(map);
         mutex_unlock(&acpi_ioremap_lock);
 
-        if (del)
-                acpi_os_remove_map(map);
+        acpi_os_map_cleanup(map);
 }
 EXPORT_SYMBOL_GPL(acpi_os_unmap_memory);
 
@@ -418,7 +416,6 @@ static int acpi_os_map_generic_address(struct acpi_generic_address *addr)
 static void acpi_os_unmap_generic_address(struct acpi_generic_address *addr)
 {
         struct acpi_ioremap *map;
-        int del;
 
         if (addr->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
                 return;
@@ -432,11 +429,10 @@ static void acpi_os_unmap_generic_address(struct acpi_generic_address *addr)
                 mutex_unlock(&acpi_ioremap_lock);
                 return;
         }
-        del = kref_put(&map->ref, acpi_kref_del_iomap);
+        acpi_os_drop_map_ref(map);
         mutex_unlock(&acpi_ioremap_lock);
 
-        if (del)
-                acpi_os_remove_map(map);
+        acpi_os_map_cleanup(map);
 }
 
 #ifdef ACPI_FUTURE_USAGE