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

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Date:   Fri, 10 Jul 2020 14:43:50 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Kanchan Joshi <joshiiitr@...il.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Jens Axboe <axboe@...nel.dk>,
        Kanchan Joshi <joshi.k@...sung.com>, viro@...iv.linux.org.uk,
        bcrl@...ck.org, Damien.LeMoal@....com, asml.silence@...il.com,
        linux-fsdevel@...r.kernel.org, Matias Bj??rling <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 Fri, Jul 10, 2020 at 06:59:45PM +0530, Kanchan Joshi wrote:
> > block doesn't work for the case of writes to files that don't have
> > to be aligned in any way.  And that I think is the more broadly
> > applicable use case than zone append on block devices.
> 
> But when can it happen that we do zone-append on a file (zonefs I
> asssume), and device returns a location (write-pointer essentially)
> which is not in multiple of 512b?

All the time.  You open a file with O_APPEND.  You write a record to
it of any kind of size, then the next write will return the position
it got written at, which can be anything.