linux-kernel - [PATCH 3.16 168/410] android: binder: use VM

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Date:   Thu, 07 Jun 2018 15:05:21 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Ganesh Mahendran" <opensource.ganesh@...il.com>,
        "Todd Kjos" <tkjos@...gle.com>, "Martijn Coenen" <maco@...roid.com>
Subject: [PATCH 3.16 168/410] android: binder: use VM_ALLOC to get vm area

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ganesh Mahendran <opensource.ganesh@...il.com>

commit aac6830ec1cb681544212838911cdc57f2638216 upstream.

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@...il.com>
Acked-by: Martijn Coenen <maco@...roid.com>
Acked-by: Todd Kjos <tkjos@...gle.com>

----
V3: update comments
V2: update comments
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/staging/android/binder.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/staging/android/binder.c
+++ b/drivers/staging/android/binder.c
@@ -2808,7 +2808,7 @@ static int binder_mmap(struct file *filp
 		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";