linux-kernel - Re: [PATCH] zonefs: do not use append if device does not support it

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Message-ID: <87r0pygjp1.fsf@metaspace.dk>
Date:   Mon, 26 Jun 2023 20:23:48 +0200
From:   "Andreas Hindborg (Samsung)" <nmi@...aspace.dk>
To:     Johannes Thumshirn <Johannes.Thumshirn@....com>
Cc:     Damien Le Moal <dlemoal@...nel.org>,
        "open list:ZONEFS FILESYSTEM" <linux-fsdevel@...r.kernel.org>,
        "gost.dev@...sung.com" <gost.dev@...sung.com>,
        Naohiro Aota <Naohiro.Aota@....com>,
        Johannes Thumshirn <jth@...nel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] zonefs: do not use append if device does not support it


Johannes Thumshirn <Johannes.Thumshirn@....com> writes:

> On 26.06.23 18:47, Andreas Hindborg wrote:
>> From: "Andreas Hindborg (Samsung)" <nmi@...aspace.dk>
>> 
>> Zonefs will try to use `zonefs_file_dio_append()` for direct sync writes even if
>> device `max_zone_append_sectors` is zero. This will cause the IO to fail as the
>> io vector is truncated to zero. It also causes a call to
>> `invalidate_inode_pages2_range()` with end set to UINT_MAX, which is probably
>> not intentional. Thus, do not use append when device does not support it.
>> 
>
> I'm sorry but I think it has been stated often enough that for Linux Zone Append
> is a mandatory feature for a Zoned Block Device. Therefore this path is essentially
> dead code as max_zone_append_sectors will always be greater than zero.
>
> So this is a clear NAK from my side.

OK, thanks for clarifying 👍 I came across this bugging out while
playing around with zone append for ublk. The code makes sense if the
stack expects append to always be present.

I didn't follow the discussion, could you reiterate why the policy is
that zoned devices _must_ support append?

Best regards,
Andreas