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>

1 files changed, 15 insertions, 13 deletions

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index f6785bced215..445f205752a2 100644
--- 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);