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From: Nitesh Shetty <nj.shetty@samsung.com>
To: Hannes Reinecke <hare@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>, Vincent Fu <vincent.fu@samsung.com>,
	Christian Brauner <brauner@kernel.org>,
	Chaitanya Kulkarni <kch@nvidia.com>,
	Sagi Grimberg <sagi@grimberg.me>,
	martin.petersen@oracle.com, Jonathan Corbet <corbet@lwn.net>,
	gost.dev@samsung.com, Anuj Gupta <anuj20.g@samsung.com>,
	linux-doc@vger.kernel.org, Mike Snitzer <snitzer@kernel.org>,
	mcgrof@kernel.org, linux-nvme@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, dm-devel@redhat.com,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Keith Busch <kbusch@kernel.org>, Christoph Hellwig <hch@lst.de>,
	Alasdair Kergon <agk@redhat.com>
Subject: Re: [dm-devel] [PATCH v15 04/12] block: add emulation for copy
Date: Mon, 11 Sep 2023 12:39:37 +0530	[thread overview]
Message-ID: <20230911070937.GB28177@green245> (raw)
In-Reply-To: <e6fc7e65-ad31-4ca2-8b1b-4d97ba32926e@suse.de>

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On Fri, Sep 08, 2023 at 08:06:38AM +0200, Hannes Reinecke wrote:
> On 9/6/23 18:38, Nitesh Shetty wrote:
> > For the devices which does not support copy, copy emulation is added.
> > It is required for in-kernel users like fabrics, where file descriptor is
> > not available and hence they can't use copy_file_range.
> > Copy-emulation is implemented by reading from source into memory and
> > writing to the corresponding destination.
> > Also emulation can be used, if copy offload fails or partially completes.
> > At present in kernel user of emulation is NVMe fabrics.
> > 
> Leave out the last sentence; I really would like to see it enabled for SCSI,
> too (we do have copy offload commands for SCSI ...).
> 
Sure, will do that

> And it raises all the questions which have bogged us down right from the
> start: where is the point in calling copy offload if copy offload is not
> implemented or slower than copying it by hand?
> And how can the caller differentiate whether copy offload bring a benefit to
> him?
> 
> IOW: wouldn't it be better to return -EOPNOTSUPP if copy offload is not
> available?

Present approach treats copy as a background operation and the idea is to
maximize the chances of achieving copy by falling back to emulation.
Having said that, it should be possible to return -EOPNOTSUPP,
in case of offload IO failure or device not supporting offload.
We will update this in next version.

Thank you,
Nitesh Shetty

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WARNING: multiple messages have this Message-ID (diff)
From: Nitesh Shetty <nj.shetty@samsung.com>
To: Hannes Reinecke <hare@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>, Jonathan Corbet <corbet@lwn.net>,
	Alasdair Kergon <agk@redhat.com>,
	Mike Snitzer <snitzer@kernel.org>,
	dm-devel@redhat.com, Keith Busch <kbusch@kernel.org>,
	Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
	Chaitanya Kulkarni <kch@nvidia.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christian Brauner <brauner@kernel.org>,
	martin.petersen@oracle.com, mcgrof@kernel.org,
	gost.dev@samsung.com, Vincent Fu <vincent.fu@samsung.com>,
	Anuj Gupta <anuj20.g@samsung.com>,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v15 04/12] block: add emulation for copy
Date: Mon, 11 Sep 2023 12:39:37 +0530	[thread overview]
Message-ID: <20230911070937.GB28177@green245> (raw)
In-Reply-To: <e6fc7e65-ad31-4ca2-8b1b-4d97ba32926e@suse.de>

[-- Attachment #1: Type: text/plain, Size: 1445 bytes --]

On Fri, Sep 08, 2023 at 08:06:38AM +0200, Hannes Reinecke wrote:
> On 9/6/23 18:38, Nitesh Shetty wrote:
> > For the devices which does not support copy, copy emulation is added.
> > It is required for in-kernel users like fabrics, where file descriptor is
> > not available and hence they can't use copy_file_range.
> > Copy-emulation is implemented by reading from source into memory and
> > writing to the corresponding destination.
> > Also emulation can be used, if copy offload fails or partially completes.
> > At present in kernel user of emulation is NVMe fabrics.
> > 
> Leave out the last sentence; I really would like to see it enabled for SCSI,
> too (we do have copy offload commands for SCSI ...).
> 
Sure, will do that

> And it raises all the questions which have bogged us down right from the
> start: where is the point in calling copy offload if copy offload is not
> implemented or slower than copying it by hand?
> And how can the caller differentiate whether copy offload bring a benefit to
> him?
> 
> IOW: wouldn't it be better to return -EOPNOTSUPP if copy offload is not
> available?

Present approach treats copy as a background operation and the idea is to
maximize the chances of achieving copy by falling back to emulation.
Having said that, it should be possible to return -EOPNOTSUPP,
in case of offload IO failure or device not supporting offload.
We will update this in next version.

Thank you,
Nitesh Shetty

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  reply	other threads:[~2023-09-11  7:28 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20230906164238epcas5p4a511a029fb8ae8bbc36b750712ad64d5@epcas5p4.samsung.com>
2023-09-06 16:38 ` [dm-devel] [PATCH v15 00/12] Implement copy offload support Nitesh Shetty
2023-09-06 16:38   ` Nitesh Shetty
2023-09-06 16:38   ` [dm-devel] [PATCH v15 01/12] block: Introduce queue limits and sysfs for copy-offload support Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-07 18:38     ` [dm-devel] " Luis Chamberlain
2023-09-07 18:38       ` Luis Chamberlain
2023-09-06 16:38   ` [dm-devel] [PATCH v15 02/12] Add infrastructure for copy offload in block and request layer Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-07  5:39     ` [dm-devel] " Hannes Reinecke
2023-09-07  5:39       ` Hannes Reinecke
2023-09-07  7:09       ` [dm-devel] " Nitesh Shetty
2023-09-07  7:09         ` Nitesh Shetty
2023-09-06 16:38   ` [dm-devel] [PATCH v15 03/12] block: add copy offload support Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-07  5:49     ` [dm-devel] " Hannes Reinecke
2023-09-07  5:49       ` Hannes Reinecke
2023-09-07  7:16       ` [dm-devel] " Nitesh Shetty
2023-09-07  7:16         ` Nitesh Shetty
2023-09-08  5:55         ` [dm-devel] " Hannes Reinecke
2023-09-08  5:55           ` Hannes Reinecke
2023-09-06 16:38   ` [dm-devel] [PATCH v15 04/12] block: add emulation for copy Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-08  6:06     ` [dm-devel] " Hannes Reinecke
2023-09-08  6:06       ` Hannes Reinecke
2023-09-11  7:09       ` Nitesh Shetty [this message]
2023-09-11  7:09         ` Nitesh Shetty
2023-09-11  7:39         ` [dm-devel] " Hannes Reinecke
2023-09-11  7:39           ` Hannes Reinecke
2023-09-11 10:20           ` [dm-devel] " Nitesh Shetty
2023-09-11 10:20             ` Nitesh Shetty
2023-09-06 16:38   ` [dm-devel] [PATCH v15 05/12] fs/read_write: Enable copy_file_range for block device Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-08  6:07     ` [dm-devel] " Hannes Reinecke
2023-09-08  6:07       ` Hannes Reinecke
2023-09-06 16:38   ` [dm-devel] [PATCH v15 06/12] fs, block: copy_file_range for def_blk_ops for direct " Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-08  6:08     ` [dm-devel] " Hannes Reinecke
2023-09-08  6:08       ` Hannes Reinecke
2023-09-06 16:38   ` [dm-devel] [PATCH v15 07/12] nvme: add copy offload support Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-08  6:09     ` [dm-devel] " Hannes Reinecke
2023-09-08  6:09       ` Hannes Reinecke
2023-09-06 16:38   ` [dm-devel] [PATCH v15 08/12] nvmet: add copy command support for bdev and file ns Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-08  6:11     ` [dm-devel] " Hannes Reinecke
2023-09-08  6:11       ` Hannes Reinecke
2023-09-06 16:38   ` [dm-devel] [PATCH v15 09/12] dm: Add support for copy offload Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-08  6:13     ` [dm-devel] " Hannes Reinecke
2023-09-08  6:13       ` Hannes Reinecke
2023-09-11  7:07       ` [dm-devel] " Nitesh Shetty
2023-09-11  7:07         ` Nitesh Shetty
2023-09-11  7:45         ` [dm-devel] " Hannes Reinecke
2023-09-11  7:45           ` Hannes Reinecke
2023-09-06 16:38   ` [dm-devel] [PATCH v15 10/12] dm: Enable copy offload for dm-linear target Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-08  6:14     ` [dm-devel] " Hannes Reinecke
2023-09-08  6:14       ` Hannes Reinecke
2023-09-06 16:38   ` [dm-devel] [PATCH v15 11/12] null: Enable trace capability for null block Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-08  6:14     ` [dm-devel] " Hannes Reinecke
2023-09-08  6:14       ` Hannes Reinecke
2023-09-06 16:38   ` [dm-devel] [PATCH v15 12/12] null_blk: add support for copy offload Nitesh Shetty
2023-09-06 16:38     ` Nitesh Shetty
2023-09-06 22:01     ` [dm-devel] " kernel test robot
2023-09-06 22:01       ` kernel test robot
2023-09-06 22:58     ` [dm-devel] " kernel test robot
2023-09-06 22:58       ` kernel test robot
2023-09-08  6:16     ` [dm-devel] " Hannes Reinecke
2023-09-08  6:16       ` Hannes Reinecke

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