linux-kernel - Re: [RFC PATCH v5 0/4] add simple copy support

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Message-ID: <YDMJdekWhy/Y1Y1r@T590>
Date:   Mon, 22 Feb 2021 09:31:33 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     SelvaKumar S <selvakuma.s1@...sung.com>
Cc:     linux-nvme@...ts.infradead.org, kbusch@...nel.org, axboe@...nel.dk,
        damien.lemoal@....com, hch@....de, sagi@...mberg.me,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        dm-devel@...hat.com, snitzer@...hat.com, selvajove@...il.com,
        joshiiitr@...il.com, nj.shetty@...sung.com, joshi.k@...sung.com,
        javier.gonz@...sung.com, kch@...nel.org,
        linux-fsdevel@...r.kernel.org, linux-scsi@...r.kernel.org,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Subject: Re: [RFC PATCH v5 0/4] add simple copy support

On Fri, Feb 19, 2021 at 06:15:13PM +0530, SelvaKumar S wrote:
> This patchset tries to add support for TP4065a ("Simple Copy Command"),
> v2020.05.04 ("Ratified")
> 
> The Specification can be found in following link.
> https://nvmexpress.org/wp-content/uploads/NVM-Express-1.4-Ratified-TPs-1.zip
> 
> Simple copy command is a copy offloading operation and is  used to copy
> multiple contiguous ranges (source_ranges) of LBA's to a single destination
> LBA within the device reducing traffic between host and device.
> 
> This implementation doesn't add native copy offload support for stacked
> devices rather copy offload is done through emulation. Possible use
> cases are F2FS gc and BTRFS relocation/balance.
> 
> *blkdev_issue_copy* takes source bdev, no of sources, array of source
> ranges (in sectors), destination bdev and destination offset(in sectors).
> If both source and destination block devices are same and copy_offload = 1,
> then copy is done through native copy offloading. Copy emulation is used
> in other cases.
> 
> As SCSI XCOPY can take two different block devices and no of source range is
> equal to 1, this interface can be extended in future to support SCSI XCOPY.

The patchset adds ioctl(BLKCOPY) and two userspace visible data
struture(range_entry, and copy_range), all belong to kabi stuff, and the
interface is generic block layer kabi.

The API has to be allowed to extend for supporting SCSI XCOPY in future or similar
block copy commands without breaking previous application, so please CC linux-scsi
and scsi guys in your next post.


-- 
Ming