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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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