linux-kernel - Re: [PATCH v2 1/2] fs,block: Introduce RWF_ZONE

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Message-ID: <20200626085846.GA24962@infradead.org>
Date:   Fri, 26 Jun 2020 09:58:46 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Kanchan Joshi <joshi.k@...sung.com>
Cc:     axboe@...nel.dk, viro@...iv.linux.org.uk, bcrl@...ck.org,
        asml.silence@...il.com, Damien.LeMoal@....com, hch@...radead.org,
        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,
        selvakuma.s1@...sung.com, nj.shetty@...sung.com,
        javier.gonz@...sung.com, Arnav Dawn <a.dawn@...sung.com>
Subject: Re: [PATCH v2 1/2] fs,block: Introduce RWF_ZONE_APPEND and handling
 in direct IO path

To restate my previous NAK:

A low-level protocol detail like RWF_ZONE_APPEND has absolutely no
business being exposed in the Linux file system interface.

And as mentioned before I think the idea of returning the actual
position written for O_APPEND writes totally makes sense, and actually
is generalizable to all files.  Together with zonefs that gives you a
perfect interface for zone append.

On Thu, Jun 25, 2020 at 10:45:48PM +0530, Kanchan Joshi wrote:
> Introduce RWF_ZONE_APPEND flag to represent zone-append.

And no one but us select few even know what zone append is, nevermind
what the detailed semantics are.  If you add a userspace API you need
to very clearly document the semantics inluding errors and corner cases.