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From: Ming Lei <[email protected]>
To: Sagi Grimberg <[email protected]>
Cc: Gabriel Krisman Bertazi <[email protected]>,
	Jens Axboe <[email protected]>,
	[email protected],
	Harris James R <[email protected]>,
	[email protected], [email protected],
	ZiyangZhang <[email protected]>,
	Xiaoguang Wang <[email protected]>,
	Stefan Hajnoczi <[email protected]>,
	[email protected]
Subject: Re: [PATCH V3 1/1] ublk: add io_uring based userspace block driver
Date: Tue, 5 Jul 2022 08:43:43 +0800	[thread overview]
Message-ID: <YsOJP9BaD0LUpsgg@T590> (raw)
In-Reply-To: <[email protected]>

On Mon, Jul 04, 2022 at 07:19:09PM +0300, Sagi Grimberg wrote:
> 
> > > > > > 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?
> 
> All I'm saying is that either we should expose it (or an interface to
> it) if it has merit, or use something else (use a workqueue).

There isn't replacement for task_work_add().

If module has to be supported, we can add one command for running the
work function in the ubq context, that will add some cost.

> Having a block driver driver builtin is probably not the answer.

Not sure, there are at least two drivers which use the API.


Thanks,
Ming


  reply	other threads:[~2022-07-05  0:44 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-28 16:08 [PATCH V3 0/1] ublk: add io_uring based userspace block driver Ming Lei
2022-06-28 16:08 ` [PATCH V3 1/1] " Ming Lei
2022-06-30 11:35   ` Ziyang Zhang
2022-06-30 12:33     ` Ming Lei
2022-07-01  2:47       ` Ziyang Zhang
2022-07-01  4:06         ` Ming Lei
2022-07-04 11:17   ` Sagi Grimberg
2022-07-04 12:34     ` Ming Lei
2022-07-04 14:00       ` Sagi Grimberg
2022-07-04 16:13         ` Gabriel Krisman Bertazi
2022-07-04 16:19           ` Sagi Grimberg
2022-07-05  0:43             ` Ming Lei [this message]
2022-07-04 22:10   ` Gabriel Krisman Bertazi
2022-07-05  4:16     ` Ziyang Zhang
2022-07-05  8:12       ` Ming Lei
2022-07-05  8:06     ` Ming Lei
2022-07-07  7:49       ` Ming Lei
2022-07-07  7:58         ` Ming Lei

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