Re: [dm-devel] [PATCH 7/8] dm: delay registering the gendisk

[Yu Kuai <yukuai1@huaweicloud.com>]

Hi, Christoph!

在 2022/07/15 11:24, Yu Kuai 写道:
> Hi, Christoph!
> 
> 在 2022/07/07 15:20, Yu Kuai 写道:
>> 在 2022/07/07 13:24, Christoph Hellwig 写道:
>>> On Thu, Jul 07, 2022 at 11:29:26AM +0800, Yu Kuai wrote:
>>>> We found that this patch fix a nullptr crash in our test:
>>>
>>>> Do you think it's ok to backport this patch(and all realted patches) to
>>>> lts, or it's better to fix that bio can be submitted with queue
>>>> uninitialized from block layer?
>>>
>>> Given how long ago this was I do not remember offhand how much prep
>>> work this would require.  The patch itself is of course tiny and
>>> backportable, but someone will need to do the work and figure out how
>>> much else would have to be backported.
>>
>> Ok, I'll try to figure out that, and backport them.(At least to 5.10.y)

I posted a stable patchset on stable 5.10, can you pleas take a loock ?

dm: fix nullptr crash
https://lore.kernel.org/all/20220729062356.1663513-1-yukuai1@huaweicloud.com/

Thanks,
Kuai
> 
> While reviewing the code, I didn't found any protection that
> bd_link_disk_holder() won't concurrent with
> bd_register_pending_holders(). If they do can concurrent,
> following scenario is problematic:
> 
> t1                t2
> device_add_disk
>   disk->slave_dir = kobject_create_and_add
>                  bd_link_disk_holder
>                   __link_disk_holder
>                   list_add
>   bd_register_pending_holders
>    list_for_each_entry
>     __link_disk_holder -> -EEXIST
> 
> In this case, I think maybe ignore '-EEXIST' is fine.
> 
> I'm not familiar with dm, and I'm not sure if I missed something,
> please kindly correct me if I'm wrong.
> 
> Thanks,
> Kuai
> 
> .
> 

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