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Date: Thu, 26 Feb 2015 16:12:49 -0800
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Subject: Re: Regression in v4.0.0-rc1 with Android Binder
From: =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= <arve@android.com>
To: Amit Pundir <amit.pundir@linaro.org>
Cc: LKML <linux-kernel@vger.kernel.org>, a.ryabinin@samsung.com,
        dvyukov@google.com, kcc@google.com, dmitryc@google.com,
        adech.fo@gmail.com, tetra2005@gmail.com, koct9i@gmail.com,
        sasha.levin@oracle.com, cl@linux.com, iamjoonsoo.kim@lge.com,
        dave.hansen@intel.com, andi@firstfloor.org,
        Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
        "H. Peter Anvin" <hpa@zytor.com>, penberg@kernel.org,
        David Rientjes <rientjes@google.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Riley Andrews <riandrews@android.com>,
        Serban Constantinescu <serban.constantinescu@arm.com>,
        John Stultz <john.stultz@linaro.org>,
        Sumit Semwal <sumit.semwal@linaro.org>
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On Thu, Feb 26, 2015 at 2:04 PM, Amit Pundir <amit.pundir@linaro.org> wrote:
> Hi,
>
> I ran into series of following binder mmap failures with v4.0.0-rc1:
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 1971 at mm/vmalloc.c:130
> vmap_page_range_noflush+0x119/0x144()
> CPU: 0 PID: 1971 Comm: healthd Not tainted 4.0.0-rc1-00399-g7da3fdc-dirty #157
> Hardware name: ARM-Versatile Express
> [<c001246d>] (unwind_backtrace) from [<c000f7f9>] (show_stack+0x11/0x14)
> [<c000f7f9>] (show_stack) from [<c049a221>] (dump_stack+0x59/0x7c)
> [<c049a221>] (dump_stack) from [<c001cf21>] (warn_slowpath_common+0x55/0x84)
> [<c001cf21>] (warn_slowpath_common) from [<c001cfe3>]
> (warn_slowpath_null+0x17/0x1c)
> [<c001cfe3>] (warn_slowpath_null) from [<c00c66c5>]
> (vmap_page_range_noflush+0x119/0x144)
> [<c00c66c5>] (vmap_page_range_noflush) from [<c00c716b>] (map_vm_area+0x27/0x48)
> [<c00c716b>] (map_vm_area) from [<c038ddaf>]
> (binder_update_page_range+0x12f/0x27c)
> [<c038ddaf>] (binder_update_page_range) from [<c038e857>]
> (binder_mmap+0xbf/0x1ac)
> [<c038e857>] (binder_mmap) from [<c00c2dc7>] (mmap_region+0x2eb/0x4d4)
> [<c00c2dc7>] (mmap_region) from [<c00c3197>] (do_mmap_pgoff+0x1e7/0x250)
> [<c00c3197>] (do_mmap_pgoff) from [<c00b35b5>] (vm_mmap_pgoff+0x45/0x60)
> [<c00b35b5>] (vm_mmap_pgoff) from [<c00c1f39>] (SyS_mmap_pgoff+0x5d/0x80)
> [<c00c1f39>] (SyS_mmap_pgoff) from [<c000ce81>] (ret_fast_syscall+0x1/0x5c)
> ---[ end trace 48c2c4b9a1349e54 ]---
> binder: 1982: binder_alloc_buf failed to map page at f0e00000 in kernel
> binder: binder_mmap: 1982 b6bde000-b6cdc000 alloc small buf failed -12
>
>
> Turned out that the following commit tripped off binder:
> ----------8<----------
> commit 71394fe50146202f2c8d92cf50f5ebc761acf254
> Author: Andrey Ryabinin <a.ryabinin@samsung.com>
> Date:   Fri Feb 13 14:40:03 2015 -0800
>
>     mm: vmalloc: add flag preventing guard hole allocation
> ---------->8----------
>
>
> Explicitly disabling the vmalloc no guard (VM_NO_GUARD) flag in binder
> worked fine for me. So does a fix like this look reasonable enough to
> submit?
> ----------8<----------
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -601,6 +601,7 @@ static int binder_update_page_range(struct
> binder_proc *proc, int allocate,
>                         goto err_alloc_page_failed;
>                 }
>                 tmp_area.addr = page_addr;
> +               tmp_area.flags &= ~VM_NO_GUARD;

This variable is not initialized, so I would expect this to add a
warning. Setting it to VM_NO_GUARD and removing, " + PAGE_SIZE /*
guard page? */" fromt he next line would be better. However, the "new"
map_kernel_range_noflush api seems like a better api to use for this,
since it removes the need to create a dummy vm_struct at all.

>                 tmp_area.size = PAGE_SIZE + PAGE_SIZE /* guard page? */;
>                 ret = map_vm_area(&tmp_area, PAGE_KERNEL, page);
>                 if (ret) {
> ---------->8----------
>
>
> Regards,
> Amit Pundir

-- 
Arve Hjønnevåg
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