linux-kernel - Re: [PATCH] mm/vmalloc: a slight change of compare target in __insert_vmap

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Message-ID: <20170603022858.GB11080@WeideMacBook-Pro.local>
Date:   Sat, 3 Jun 2017 10:28:58 +0800
From:   Wei Yang <richard.weiyang@...il.com>
To:     zhong jiang <zhongjiang@...wei.com>
Cc:     Wei Yang <richard.weiyang@...il.com>, akpm@...ux-foundation.org,
        mhocko@...e.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmalloc: a slight change of compare target in
 __insert_vmap_area()

On Fri, Jun 02, 2017 at 10:26:06AM +0800, zhong jiang wrote:
>On 2017/6/2 9:45, Wei Yang wrote:
>> On Fri, May 26, 2017 at 09:55:31AM +0800, zhong jiang wrote:
>>> On 2017/5/26 9:36, Wei Yang wrote:
>>>> On Thu, May 25, 2017 at 11:04:44AM +0800, zhong jiang wrote:
>>>>> I hit the overlap issue, but it  is hard to reproduced. if you think it is safe. and the situation
>>>>> is not happen. AFAIC, it is no need to add the code.
>>>>>
>>>>> if you insist on the point. Maybe VM_WARN_ON is a choice.
>>>>>
>>>> Do you have some log to show the overlap happens?
>>> Hi  wei
>>>
>>> cat /proc/vmallocinfo
>>> 0xf1580000-0xf1600000  524288 raw_dump_mem_write+0x10c/0x188 phys=8b901000 ioremap
>>> 0xf1638000-0xf163a000    8192 mcss_pou_queue_init+0xa0/0x13c [mcss] phys=fc614000 ioremap
>>> 0xf528e000-0xf5292000   16384 n_tty_open+0x10/0xd0 pages=3 vmalloc
>>> 0xf5000000-0xf9001000 67112960 devm_ioremap+0x38/0x70 phys=40000000 ioremap
>> These two ranges overlap.
>>
>> This is hard to say where is the problem. From the code point of view, I don't
>> see there is possibility to allocate an overlapped range.
>>
>> Which version of your kernel?
>> Hard to reproduce means just see once? 
>  yes, just once.  I have also no see any problem from the code.   The kernel version is linux 4.1.
> but That indeed exist. 
>

This is really interesting. While without reproducing the behavior, it is
really costly to debug in the code.

I took a look into my own /proc/vmallocinfo, there are around hundred entries.
Currently, I don't have a clue to dive into the issue.

> Thanks
>zhongjiang
>>> 0xfe001000-0xfe002000    4096 iotable_init+0x0/0xc phys=20001000 ioremap
>>> 0xfe200000-0xfe201000    4096 iotable_init+0x0/0xc phys=1a000000 ioremap
>>> 0xff100000-0xff101000    4096 iotable_init+0x0/0xc phys=2000a000 ioremap
>>>
>>> I hit the above issue, but the log no more useful info. it just is found by accident.
>>> and it is hard to reprodeced. no more info can be supported for further investigation.
>>> therefore, it is no idea for me. 
>>>
>>> Thanks
>>> zhongjinag
>>>
>

-- 
Wei Yang
Help you, Help me

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