ACPI: Make acpi_os_map_memory() avoid creating unnecessary mappings

Modify acpi_os_map_memory() so that it doesn't call acpi_os_ioremap()
unconditionally every time it is executed (except when
acpi_gbl_permanent_mmap is unset), which pretty much defeats the
purpose of maintaining the list of ACPI iomaps in osl.c.

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

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index f6785bced215b9d99b899fa6f769ad0074d3efe1..445f205752a249baea812532899cbfb35bdee8ec 100644 (file)
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -302,7 +302,7 @@ acpi_map_lookup_virt(void __iomem *virt, acpi_size size)
 void __iomem *__init_refok
 acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
 {
-       struct acpi_ioremap *map, *tmp_map;
+       struct acpi_ioremap *map;
        void __iomem *virt;
        acpi_physical_address pg_off;
        acpi_size pg_sz;
@@ -315,14 +315,25 @@ acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
        if (!acpi_gbl_permanent_mmap)
                return __acpi_map_table((unsigned long)phys, size);
 
+       mutex_lock(&acpi_ioremap_lock);
+       /* Check if there's a suitable mapping already. */
+       map = acpi_map_lookup(phys, size);
+       if (map) {
+               kref_get(&map->ref);
+               goto out;
+       }
+
        map = kzalloc(sizeof(*map), GFP_KERNEL);
-       if (!map)
+       if (!map) {
+               mutex_unlock(&acpi_ioremap_lock);
                return NULL;
+       }
 
        pg_off = round_down(phys, PAGE_SIZE);
        pg_sz = round_up(phys + size, PAGE_SIZE) - pg_off;
        virt = acpi_os_ioremap(pg_off, pg_sz);
        if (!virt) {
+               mutex_unlock(&acpi_ioremap_lock);
                kfree(map);
                return NULL;
        }
@@ -333,19 +344,10 @@ acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
        map->size = pg_sz;
        kref_init(&map->ref);
 
-       mutex_lock(&acpi_ioremap_lock);
-       /* Check if page has already been mapped. */
-       tmp_map = acpi_map_lookup(phys, size);
-       if (tmp_map) {
-               kref_get(&tmp_map->ref);
-               mutex_unlock(&acpi_ioremap_lock);
-               iounmap(map->virt);
-               kfree(map);
-               return tmp_map->virt + (phys - tmp_map->phys);
-       }
        list_add_tail_rcu(&map->list, &acpi_ioremaps);
-       mutex_unlock(&acpi_ioremap_lock);
 
+ out:
+       mutex_unlock(&acpi_ioremap_lock);
        return map->virt + (phys - map->phys);
 }
 EXPORT_SYMBOL_GPL(acpi_os_map_memory);