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

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Date:   Tue, 7 Jan 2020 15:32:58 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Ming Lei <ming.lei@...hat.com>, Guenter Roeck <linux@...ck-us.net>
Cc:     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 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!

-- 
Jens Axboe