linux-kernel - Re: [PATCH] block: fix splitting segments

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Date:   Tue, 7 Jan 2020 19:36:08 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Guenter Roeck <linux@...ck-us.net>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, Chris Mason <clm@...com>
Subject: Re: [PATCH] block: fix splitting segments

On 1/7/20 6:59 PM, Ming Lei wrote:
> On Tue, Jan 07, 2020 at 03:32:58PM -0700, Jens Axboe wrote:
>> On 1/7/20 3:30 PM, Ming Lei wrote:
>>> On Tue, Jan 07, 2020 at 10:11:45AM -0800, Guenter Roeck wrote:
>>>> On Tue, Jan 07, 2020 at 11:23:39PM +0800, Ming Lei wrote:
>>>>> On Tue, Jan 07, 2020 at 04:47:08AM -0800, Guenter Roeck wrote:
>>>>>> Hi,
>>>>>>
>>>>>> On Sun, Dec 29, 2019 at 10:32:30AM +0800, Ming Lei wrote:
>>>>>>> There are two issues in get_max_segment_size():
>>>>>>>
>>>>>>> 1) the default segment boudary mask is bypassed, and some devices still
>>>>>>> require segment to not cross the default 4G boundary
>>>>>>>
>>>>>>> 2) the segment start address isn't taken into account when checking
>>>>>>> segment boundary limit
>>>>>>>
>>>>>>> Fixes the two issues.
>>>>>>>
>>>>>>> Fixes: dcebd755926b ("block: use bio_for_each_bvec() to compute multi-page bvec count")
>>>>>>> Signed-off-by: Ming Lei <ming.lei@...hat.com>
>>>>>>
>>>>>> This patch, pushed into mainline as "block: fix splitting segments on
>>>>>> boundary masks", results in the following crash when booting 'versatilepb'
>>>>>> in qemu from disk. Bisect log is attached. Detailed log is at
>>>>>> https://kerneltests.org/builders/qemu-arm-master/builds/1410/steps/qemubuildcommand/logs/stdio
>>>>>>
>>>>>> Guenter
>>>>>>
>>>>>> ---
>>>>>> Crash:
>>>>>>
>>>>>> kernel BUG at block/bio.c:1885!
>>>>>> Internal error: Oops - BUG: 0 [#1] ARM
>>>>>
>>>>> Please apply the following debug patch, and post the log.
>>>>>
>>>>
>>>> Here you are:
>>>>
>>>> max_sectors 2560 max_segs 96 max_seg_size 65536 mask ffffffff
>>>> c738da80: 8c80/0 2416 28672, 0
>>>>          total sectors 56
>>>>
>>>> (I replaced %p with %px).
>>>>
>>>
>>> Please try the following patch and see if it makes a difference.
>>> If not, replace trace_printk with printk in previous debug patch,
>>> and apply the debug patch only & post the log.
>>
>> If it is a 32-bit issue, then we should use a 64-bit type to make
>> this nicer than ULL. But it seems reasonable that it could be!
> 
> oops, just saw this email after sending out the patch.
> 
> Do you need V2 to change ULL to u64?

Nah, I can just edit it, that's fine.

-- 
Jens Axboe