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

[Andreas Hindborg (Samsung)]

Damien Le Moal <dlemoal@xxxxxxxxxx> 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@xxxxxxxxxxxx>
>>>
>>> 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