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

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Date:   Tue, 27 Jun 2023 07:14:58 +0200
From:   "Andreas Hindborg (Samsung)" <nmi@...aspace.dk>
To:     Damien Le Moal <dlemoal@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        "open list:ZONEFS FILESYSTEM" <linux-fsdevel@...r.kernel.org>,
        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


Damien Le Moal <dlemoal@...nel.org> writes:

> On 6/27/23 12:45, Christoph Hellwig wrote:
>> On Mon, Jun 26, 2023 at 06:47:52PM +0200, 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.
>> 
>> How do you even manage to hit this code?  Zone Append is a mandatory
>> feature and driver need to check it is available.
>
> ublk driver probably is missing that check ? I have not looked at the code for
> zone support.
>
> But thinking of it, we probably would be better off having a generic check for
> "q->limits.max_zone_append_sectors != 0" in blk_revalidate_disk_zones().

I was playing with ublk zone support. It seems I made it buggy by
allowing zone append size to go to zero.

Adding the check would be a nice help to people like me that will
implement whatever in their driver :)

Best regards
Andreas