Re: [PATCH RFC v4 12/15] io_uring/cmd: let cmds to know about dying task

[Bernd Schubert <bschubert@ddn.com>]

On 11/4/24 01:28, Pavel Begunkov wrote:
> On 10/16/24 01:05, Bernd Schubert wrote:
>> From: Pavel Begunkov <asml.silence@gmail.com>
>>
>> When the taks that submitted a request is dying, a task work for that
>> request might get run by a kernel thread or even worse by a half
>> dismantled task. We can't just cancel the task work without running the
>> callback as the cmd might need to do some clean up, so pass a flag
>> instead. If set, it's not safe to access any task resources and the
>> callback is expected to cancel the cmd ASAP.
>>
>> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
>> ---
>>   include/linux/io_uring_types.h | 1 +
>>   io_uring/uring_cmd.c           | 6 +++++-
>>   2 files changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/io_uring_types.h
>> b/include/linux/io_uring_types.h
>> index
>> 7abdc09271245ff7de3fb9a905ca78b7561e37eb..869a81c63e4970576155043fce7fe656293d7f58 100644
>> --- a/include/linux/io_uring_types.h
>> +++ b/include/linux/io_uring_types.h
>> @@ -37,6 +37,7 @@ enum io_uring_cmd_flags {
>>       /* set when uring wants to cancel a previously issued command */
>>       IO_URING_F_CANCEL        = (1 << 11),
>>       IO_URING_F_COMPAT        = (1 << 12),
>> +    IO_URING_F_TASK_DEAD        = (1 << 13),
>>   };
>>     struct io_wq_work_node {
>> diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
>> index
>> 21ac5fb2d5f087e1174d5c94815d580972db6e3f..82c6001cc0696bbcbebb92153e1461f2a9aeebc3 100644
>> --- a/io_uring/uring_cmd.c
>> +++ b/io_uring/uring_cmd.c
>> @@ -119,9 +119,13 @@ EXPORT_SYMBOL_GPL(io_uring_cmd_mark_cancelable);
>>   static void io_uring_cmd_work(struct io_kiocb *req, struct
>> io_tw_state *ts)
>>   {
>>       struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct
>> io_uring_cmd);
>> +    unsigned int flags = IO_URING_F_COMPLETE_DEFER;
>> +
>> +    if (req->task != current)
>> +        flags |= IO_URING_F_TASK_DEAD;
> 
> Bernd, please don't change patches under my name without any
> notice. This check is wrong, just stick to the original
> 
> https://lore.kernel.org/io-uring/d2528a1c-3d7c-4124-953c-02e8e415529e@gmail.com/
> 
> In general if you need to change something, either stick your
> name, so that I know it might be a derivative, or reflect it in
> the commit message, e.g.
> 
> Signed-off-by: initial author
> [Person 2: changed this and that]
> Signed-off-by: person 2

Oh sorry, for sure. I totally forgot to update the commit message.

Somehow the initial version didn't trigger. I need to double check to
see if there wasn't a testing issue on my side - going to check tomorrow.


> 
> Also, a quick note that btrfs also need the patch, so it'll likely
> get queued via either io_uring or btrfs trees for next.

Thanks, good to know, one patch less to carry :)



Thanks,
Bernd