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

Ganesh Mahendran
2018-01-10T02:49:16Z

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(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 07b866a..5a426c8 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -670,7 +670,7 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc,
goto err_already_mapped;
}

- area = get_vm_area(vma->vm_end - vma->vm_start, VM_IOREMAP);
+ area = get_vm_area(vma->vm_end - vma->vm_start, VM_ALLOC);
if (area == NULL) {
ret = -ENOMEM;
failure_string = "get_vm_area";
--
1.9.1