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From:   "javier.gonz@samsung.com" <javier@javigon.com>
Date:   Thu, 18 Jun 2020 10:35:29 +0200
To:     Damien Le Moal <Damien.LeMoal@wdc.com>
Cc:     Kanchan Joshi <joshi.k@samsung.com>,
        "axboe@kernel.dk" <axboe@kernel.dk>,
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        "io-uring@vger.kernel.org" <io-uring@vger.kernel.org>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "selvakuma.s1@samsung.com" <selvakuma.s1@samsung.com>,
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Subject: Re: [PATCH 3/3] io_uring: add support for zone-append
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On 18.06.2020 07:39, Damien Le Moal wrote:
>On 2020/06/18 2:27, Kanchan Joshi wrote:
>> From: Selvakumar S <selvakuma.s1@samsung.com>
>>
>> Introduce three new opcodes for zone-append -
>>
>>    IORING_OP_ZONE_APPEND     : non-vectord, similiar to IORING_OP_WRITE
>>    IORING_OP_ZONE_APPENDV    : vectored, similar to IORING_OP_WRITEV
>>    IORING_OP_ZONE_APPEND_FIXED : append using fixed-buffers
>>
>> Repurpose cqe->flags to return zone-relative offset.
>>
>> Signed-off-by: SelvaKumar S <selvakuma.s1@samsung.com>
>> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
>> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
>> Signed-off-by: Javier Gonzalez <javier.gonz@samsung.com>
>> ---
>>  fs/io_uring.c                 | 72 +++++++++++++++++++++++++++++++++++++++++--
>>  include/uapi/linux/io_uring.h |  8 ++++-
>>  2 files changed, 77 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index 155f3d8..c14c873 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -649,6 +649,10 @@ struct io_kiocb {
>>  	unsigned long		fsize;
>>  	u64			user_data;
>>  	u32			result;
>> +#ifdef CONFIG_BLK_DEV_ZONED
>> +	/* zone-relative offset for append, in bytes */
>> +	u32			append_offset;
>
>this can overflow. u64 is needed.

We chose to do it this way to start with because struct io_uring_cqe
only has space for u32 when we reuse the flags.

We can of course create a new cqe structure, but that will come with
larger changes to io_uring for supporting append.

Do you believe this is a better approach?

Javier