Re: [PATCH v3] android: binder: use VM_ALLOC to get vm area

Todd Kjos
2018-01-22T17:03:01Z

On Mon, Jan 22, 2018 at 7:54 AM, Greg KH <gregkh@linuxfoundation.org> wrote:
> On Wed, Jan 10, 2018 at 10:49:05AM +0800, Ganesh Mahendran wrote:
>> VM_IOREMAP is used to access hardware through a mechanism called
>> I/O mapped memory. Android binder is a IPC machanism which will
>> not access I/O memory.
>>
>> And VM_IOREMAP has alignment requiement which may not needed in
>> binder.
>> __get_vm_area_node()
>> {
>> ...
>> if (flags & VM_IOREMAP)
>> align = 1ul << clamp_t(int, fls_long(size),
>> PAGE_SHIFT, IOREMAP_MAX_ORDER);
>> ...
>> }
>>
>> This patch will save some kernel vm area, especially for 32bit os.
>>
>> In 32bit OS, kernel vm area is only 240MB. We may got below
>> error when launching a app:
>>
>> <3>[ 4482.440053] binder_alloc: binder_alloc_mmap_handler: 15728 8ce67000-8cf65000 get_vm_area failed -12
>> <3>[ 4483.218817] binder_alloc: binder_alloc_mmap_handler: 15745 8ce67000-8cf65000 get_vm_area failed -12
>>
>> Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.com>
>> ----
>> V3: update comments
>> V2: update comments
>> ---
>> drivers/android/binder_alloc.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Martijn and Todd, any objections to this patch?

Looks fine to me. Arve, do you remember the rationale for using VM_IOREMAP?

>
> thanks,
>
> greg k-h