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    Subject[PATCH 6/11] ACPI: Avoid walking the list of iomaps in osl.c twice in a row
    Date
    From: Rafael J. Wysocki <rjw@sisk.pl>

    Make acpi_os_unmap_generic_address() use acpi_map_lookup() to find
    the desired iomap and drop the reference to it directly (and
    eventually remove it if necessary) instead of calling
    acpi_os_unmap_memory(), which requires us to walk the list of ACPI
    iomaps twice in a row (first, to get the virtual address associated
    with the iomap and second, to get the iomap itself).

    Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
    ---
    drivers/acpi/osl.c | 33 ++++++++++++++++++++-------------
    1 file changed, 20 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
    @@ -358,6 +358,13 @@ static void acpi_kref_del_iomap(struct k
    list_del_rcu(&map->list);
    }

    +static void acpi_os_remove_map(struct acpi_ioremap *map)
    +{
    + synchronize_rcu();
    + iounmap(map->virt);
    + kfree(map);
    +}
    +
    void __ref acpi_os_unmap_memory(void __iomem *virt, acpi_size size)
    {
    struct acpi_ioremap *map;
    @@ -372,20 +379,14 @@ void __ref acpi_os_unmap_memory(void __i
    map = acpi_map_lookup_virt(virt, size);
    if (!map) {
    mutex_unlock(&acpi_ioremap_lock);
    - printk(KERN_ERR PREFIX "%s: bad address %p\n", __func__, virt);
    - dump_stack();
    + WARN(true, PREFIX "%s: bad address %p\n", __func__, virt);
    return;
    }
    -
    del = kref_put(&map->ref, acpi_kref_del_iomap);
    mutex_unlock(&acpi_ioremap_lock);

    - if (!del)
    - return;
    -
    - synchronize_rcu();
    - iounmap(map->virt);
    - kfree(map);
    + if (del)
    + acpi_os_remove_map(map);
    }
    EXPORT_SYMBOL_GPL(acpi_os_unmap_memory);

    @@ -414,8 +415,8 @@ static int acpi_os_map_generic_address(s

    static void acpi_os_unmap_generic_address(struct acpi_generic_address *addr)
    {
    - void __iomem *virt;
    - acpi_size size = addr->bit_width / 8;
    + struct acpi_ioremap *map;
    + int del;

    if (addr->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
    return;
    @@ -424,10 +425,16 @@ static void acpi_os_unmap_generic_addres
    return;

    mutex_lock(&acpi_ioremap_lock);
    - virt = acpi_map_vaddr_lookup(addr->address, size);
    + map = acpi_map_lookup(addr->address, addr->bit_width / 8);
    + if (!map) {
    + mutex_unlock(&acpi_ioremap_lock);
    + return;
    + }
    + del = kref_put(&map->ref, acpi_kref_del_iomap);
    mutex_unlock(&acpi_ioremap_lock);

    - acpi_os_unmap_memory(virt, size);
    + if (del)
    + acpi_os_remove_map(map);
    }

    #ifdef ACPI_FUTURE_USAGE


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