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>

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 445f205752a249baea812532899cbfb35bdee8ec..5389f9f2e2ffdca44ece2502147a231bcf8c3dec 100644 (file)
--- 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