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Date:   Fri, 10 Jul 2020 14:10:54 +0100
From:   Christoph Hellwig <hch@infradead.org>
To:     Kanchan Joshi <joshiiitr@gmail.com>
Cc:     Jens Axboe <axboe@kernel.dk>,
        Christoph Hellwig <hch@infradead.org>,
        Kanchan Joshi <joshi.k@samsung.com>, viro@zeniv.linux.org.uk,
        bcrl@kvack.org, Damien.LeMoal@wdc.com, asml.silence@gmail.com,
        linux-fsdevel@vger.kernel.org, Matias Bj??rling <mb@lightnvm.io>,
        linux-kernel@vger.kernel.org, linux-aio@kvack.org,
        io-uring@vger.kernel.org, linux-block@vger.kernel.org,
        Selvakumar S <selvakuma.s1@samsung.com>,
        Nitesh Shetty <nj.shetty@samsung.com>,
        Javier Gonzalez <javier.gonz@samsung.com>
Subject: Re: [PATCH v3 4/4] io_uring: add support for zone-append
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On Fri, Jul 10, 2020 at 12:35:43AM +0530, Kanchan Joshi wrote:
> Append required special treatment (conversion for sector to bytes) for io_uring.
> And we were planning a user-space wrapper to abstract that.
> 
> But good part (as it seems now) was: append result went along with cflags at
> virtually no additional cost. And uring code changes became super clean/minimal
> with further revisions.
> While indirect-offset requires doing allocation/mgmt in application,
> io-uring submission
> and in completion path (which seems trickier), and those CQE flags
> still get written
> user-space and serve no purpose for append-write.

I have to say that storing the results in the CQE generally make
so much more sense.  I wonder if we need a per-fd "large CGE" flag
that adds two extra u64s to the CQE, and some ops just require this
version.