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From:   Gabriel Krisman Bertazi <krisman@collabora.com>
To:     Sagi Grimberg <sagi@grimberg.me>
Cc:     Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>,
        linux-block@vger.kernel.org,
        Harris James R <james.r.harris@intel.com>,
        linux-kernel@vger.kernel.org, io-uring@vger.kernel.org,
        ZiyangZhang <ZiyangZhang@linux.alibaba.com>,
        Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>,
        Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: [PATCH V3 1/1] ublk: add io_uring based userspace block driver
Organization: Collabora
References: <20220628160807.148853-1-ming.lei@redhat.com>
        <20220628160807.148853-2-ming.lei@redhat.com>
        <da861bbb-1506-7598-fa06-32201456967d@grimberg.me>
        <YsLeR1QWPmqfNAQY@T590>
        <8cf1aef0-ea5b-a3df-266d-ae67674c96ae@grimberg.me>
Date:   Mon, 04 Jul 2022 12:13:18 -0400
In-Reply-To: <8cf1aef0-ea5b-a3df-266d-ae67674c96ae@grimberg.me> (Sagi
        Grimberg's message of "Mon, 4 Jul 2022 17:00:10 +0300")
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Sagi Grimberg <sagi@grimberg.me> writes:

>>>> diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
>>>> index fdb81f2794cd..d218089cdbec 100644
>>>> --- a/drivers/block/Kconfig
>>>> +++ b/drivers/block/Kconfig
>>>> @@ -408,6 +408,12 @@ config BLK_DEV_RBD
>>>>    	  If unsure, say N.
>>>> +config BLK_DEV_UBLK
>>>> +	bool "Userspace block driver"
>>>
>>> Really? why compile this to the kernel and not tristate as loadable
>>> module?
>> So far, this is only one reason: task_work_add() is required, which
>> isn't exported for modules.
>
> So why not exporting it?
> Doesn't seem like a good justification to build it into the kernel.

Sagi,

If I understand correctly, the task_work_add function is quite a core
API that we probably want to avoid exposing directly to (out-of-tree)
modules?  I agree, though, it would be great to have this buildable as a
module for general use cases.  Would it make sense to have it exposed
through a thin built-in wrapper, specific to UBD, which is exported, and
therefore able to invoke that function?  Is it a reasonable approach?

-- 
Gabriel Krisman Bertazi