Re: Lockdep warning on io_file_data_ref_zero() with 5.10-rc5

[Jens Axboe <axboe@kernel.dk>]

On 11/28/20 5:13 PM, Pavel Begunkov wrote:
> On 28/11/2020 23:59, Nadav Amit wrote:
>> Hello Pavel,
>>
>> I got the following lockdep splat while rebasing my work on 5.10-rc5 on the
>> kernel (based on 5.10-rc5+).
>>
>> I did not actually confirm that the problem is triggered without my changes,
>> as my iouring workload requires some kernel changes (not iouring changes),
>> yet IMHO it seems pretty clear that this is a result of your commit
>> e297822b20e7f ("io_uring: order refnode recycling”), that acquires a lock in
>> io_file_data_ref_zero() inside a softirq context.
> 
> Yeah, that's true. It was already reported by syzkaller and fixed by Jens, but
> queued for 5.11. Thanks for letting know anyway!
> 
> https://lore.kernel.org/io-uring/948d2d3b-5f36-034d-28e6-7490343a5b59@kernel.dk/T/#t
> 
> 
> Jens, I think it's for the best to add it for 5.10, at least so that lockdep
> doesn't complain.

Yeah maybe, though it's "just" a lockdep issue, it can't trigger any
deadlocks. I'd rather just keep it in 5.11 and ensure it goes to stable.
This isn't new in this series.

-- 
Jens Axboe