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Subject[PATCH 5/8] ACPI: Make acpi_os_map_memory() avoid creating unnecessary mappings
Date
From: Rafael J. Wysocki <rjw@sisk.pl>

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>
---
drivers/acpi/osl.c | 28 +++++++++++++++-------------
1 file changed, 15 insertions(+), 13 deletions(-)
Index: linux-2.6/drivers/acpi/osl.c
===================================================================
--- linux-2.6.orig/drivers/acpi/osl.c
+++ linux-2.6/drivers/acpi/osl.c
@@ -302,7 +302,7 @@ acpi_map_lookup_virt(void __iomem *virt,
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
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
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);


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