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From: Ming Lei <[email protected]>
To: Miklos Szeredi <[email protected]>
Cc: Linus Torvalds <[email protected]>,
	Jens Axboe <[email protected]>,
	[email protected], [email protected],
	[email protected],
	Alexander Viro <[email protected]>,
	Stefan Hajnoczi <[email protected]>,
	Miklos Szeredi <[email protected]>,
	Bernd Schubert <[email protected]>,
	Nitesh Shetty <[email protected]>,
	Christoph Hellwig <[email protected]>,
	Ziyang Zhang <[email protected]>,
	[email protected]
Subject: Re: [PATCH 1/4] fs/splice: enhance direct pipe & splice for moving pages in kernel
Date: Wed, 15 Feb 2023 08:11:05 +0800	[thread overview]
Message-ID: <Y+wjGZO6rVw5W35T@T590> (raw)
In-Reply-To: <CAJfpeguGayE2fS2m9U7=Up4Eqa_89oTeR4xW-WbcfjJBRaYqHA@mail.gmail.com>

On Tue, Feb 14, 2023 at 04:39:01PM +0100, Miklos Szeredi wrote:
> On Tue, 14 Feb 2023 at 15:35, Ming Lei <[email protected]> wrote:
> 
> > I understand it isn't one issue from block device driver viewpoint at
> > least, since the WRITE to buffer in sink end can be thought as DMA
> > to buffer from device, and it is the upper layer(FS)'s responsibility
> > for updating page flag. And block driver needn't to handle page
> > status update.
> 
> The block device still needs to know when the DMA is finished, right?

Yeah, for normal in-kernel device driver, the completion is triggered by
interrupt or io polling.

For ublk, io handling is done by userspace, here we use io_uring to
handle the IO in aio style. When the aio is completed, the userspace
gets notified of the completion.

Here the way is basically same with loop dio mode(losetup --direct-io=on),
it is still zero copy, pages from loop block driver are passed to FS(backing file)
directly for handling the original IO.


Thanks, 
Ming


  reply	other threads:[~2023-02-15  0:12 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-10 15:32 [PATCH 0/4] io_uring: add IORING_OP_READ[WRITE]_SPLICE_BUF Ming Lei
2023-02-10 15:32 ` [PATCH 1/4] fs/splice: enhance direct pipe & splice for moving pages in kernel Ming Lei
2023-02-11 15:42   ` Ming Lei
2023-02-11 18:57     ` Linus Torvalds
2023-02-12  1:39       ` Ming Lei
2023-02-13 20:04         ` Linus Torvalds
2023-02-14  0:52           ` Ming Lei
2023-02-14  2:35             ` Ming Lei
2023-02-14 11:03           ` Miklos Szeredi
2023-02-14 14:35             ` Ming Lei
2023-02-14 15:39               ` Miklos Szeredi
2023-02-15  0:11                 ` Ming Lei [this message]
2023-02-15 10:36                   ` Miklos Szeredi
2023-02-10 15:32 ` [PATCH 2/4] fs/splice: allow to ignore signal in __splice_from_pipe Ming Lei
2023-02-10 15:32 ` [PATCH 3/4] io_uring: add IORING_OP_READ[WRITE]_SPLICE_BUF Ming Lei
2023-02-11 15:45   ` Jens Axboe
2023-02-11 16:12     ` Ming Lei
2023-02-11 16:52       ` Jens Axboe
2023-02-12  3:22         ` Ming Lei
2023-02-12  3:55           ` Jens Axboe
2023-02-13  1:06             ` Ming Lei
2023-02-11 17:13   ` Jens Axboe
2023-02-12  1:48     ` Ming Lei
2023-02-12  2:42       ` Jens Axboe
2023-02-10 15:32 ` [PATCH 4/4] ublk_drv: support splice based read/write zero copy Ming Lei
2023-02-10 21:54 ` [PATCH 0/4] io_uring: add IORING_OP_READ[WRITE]_SPLICE_BUF Jens Axboe
2023-02-10 22:19   ` Jens Axboe
2023-02-11  5:13   ` Ming Lei
2023-02-11 15:45     ` Jens Axboe
2023-02-14 16:36 ` Stefan Hajnoczi

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