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Date:   Fri, 19 Jun 2020 00:51:53 +0530
From:   Kanchan Joshi <joshi.k@samsung.com>
To:     Matias =?utf-8?B?QmrDuHJsaW5n?= <mb@lightnvm.io>
Cc:     axboe@kernel.dk, viro@zeniv.linux.org.uk, bcrl@kvack.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-aio@kvack.org, io-uring@vger.kernel.org,
        linux-block@vger.kernel.org, selvakuma.s1@samsung.com,
        nj.shetty@samsung.com, javier.gonz@samsung.com,
        Damien Le Moal <Damien.LeMoal@wdc.com>,
        Keith Busch <keith.busch@wdc.com>,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 0/3] zone-append support in aio and io-uring
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On Thu, Jun 18, 2020 at 10:04:32AM +0200, Matias Bjørling wrote:
>On 17/06/2020 19.23, Kanchan Joshi wrote:
>>This patchset enables issuing zone-append using aio and io-uring direct-io interface.
>>
>>For aio, this introduces opcode IOCB_CMD_ZONE_APPEND. Application uses start LBA
>>of the zone to issue append. On completion 'res2' field is used to return
>>zone-relative offset.
>>
>>For io-uring, this introduces three opcodes: IORING_OP_ZONE_APPEND/APPENDV/APPENDV_FIXED.
>>Since io_uring does not have aio-like res2, cqe->flags are repurposed to return zone-relative offset
>
>Please provide a pointers to applications that are updated and ready 
>to take advantage of zone append.
>
>I do not believe it's beneficial at this point to change the libaio 
>API, applications that would want to use this API, should anyway 
>switch to use io_uring.
>
>Please also note that applications and libraries that want to take 
>advantage of zone append, can already use the zonefs file-system, as 
>it will use the zone append command when applicable.

AFAIK, zonefs uses append while serving synchronous I/O. And append bio
is waited upon synchronously. That maybe serving some purpose I do
not know currently. But it seems applications using zonefs file
abstraction will get benefitted if they could use the append themselves to
carry the I/O, asynchronously.

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