linux-kernel - Re: [PATCH v3 4/4] io_uring: add support for zone-append

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Date:   Mon, 6 Jul 2020 19:28:39 +0530
From:   Kanchan Joshi <joshi.k@...sung.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     viro@...iv.linux.org.uk, bcrl@...ck.org, hch@...radead.org,
        Damien.LeMoal@....com, asml.silence@...il.com,
        linux-fsdevel@...r.kernel.org, mb@...htnvm.io,
        linux-kernel@...r.kernel.org, linux-aio@...ck.org,
        io-uring@...r.kernel.org, linux-block@...r.kernel.org,
        Selvakumar S <selvakuma.s1@...sung.com>,
        Nitesh Shetty <nj.shetty@...sung.com>,
        Javier Gonzalez <javier.gonz@...sung.com>
Subject: Re: [PATCH v3 4/4] io_uring: add support for zone-append

On Sun, Jul 05, 2020 at 03:00:47PM -0600, Jens Axboe wrote:
>On 7/5/20 12:47 PM, Kanchan Joshi wrote:
>> From: Selvakumar S <selvakuma.s1@...sung.com>
>>
>> For zone-append, block-layer will return zone-relative offset via ret2
>> of ki_complete interface. Make changes to collect it, and send to
>> user-space using cqe->flags.
>>
>> Signed-off-by: Selvakumar S <selvakuma.s1@...sung.com>
>> Signed-off-by: Kanchan Joshi <joshi.k@...sung.com>
>> Signed-off-by: Nitesh Shetty <nj.shetty@...sung.com>
>> Signed-off-by: Javier Gonzalez <javier.gonz@...sung.com>
>> ---
>>  fs/io_uring.c | 21 +++++++++++++++++++--
>>  1 file changed, 19 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index 155f3d8..cbde4df 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -402,6 +402,8 @@ struct io_rw {
>>  	struct kiocb			kiocb;
>>  	u64				addr;
>>  	u64				len;
>> +	/* zone-relative offset for append, in sectors */
>> +	u32			append_offset;
>>  };
>
>I don't like this very much at all. As it stands, the first cacheline
>of io_kiocb is set aside for request-private data. io_rw is already
>exactly 64 bytes, which means that you're now growing io_rw beyond
>a cacheline and increasing the size of io_kiocb as a whole.
>
>Maybe you can reuse io_rw->len for this, as that is only used on the
>submission side of things.

Yes, this will be good. Thanks.