linux-kernel - Re: [PATCH v2] null_blk: add support for max open/active zone limit for zoned devices

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Message-ID: <20200828072253.GA1331347@apples.localdomain>
Date:   Fri, 28 Aug 2020 09:22:53 +0200
From:   Klaus Jensen <its@...elevant.dk>
To:     Damien Le Moal <Damien.LeMoal@....com>
Cc:     Niklas Cassel <Niklas.Cassel@....com>,
        Jens Axboe <axboe@...nel.dk>,
        Johannes Thumshirn <Johannes.Thumshirn@....com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] null_blk: add support for max open/active zone limit
 for zoned devices

On Aug 28 07:06, Damien Le Moal wrote:
> On 2020/08/27 22:50, Niklas Cassel wrote:
> > +static blk_status_t null_finish_zone(struct nullb_device *dev, struct blk_zone *zone)
> > +{
> > +	if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
> > +		return BLK_STS_IOERR;
> > +
> > +	switch (zone->cond) {
> > +	case BLK_ZONE_COND_FULL:
> > +		/* finish operation on full is not an error */
> > +		return BLK_STS_OK;
> > +	case BLK_ZONE_COND_EMPTY:
> > +		if (!null_manage_zone_resources(dev, zone))
> 
> OK. So you are hitting a fuzzy case here that is not actually well described in
> the standards. That is, does finishing an empty zone necessarilly imply a
> temporary transition through imp open ? Which you are assuming is a yes here.
> Personally, I would say that is not necessary, but no strong feeling either way.
> 

For ZNS, the spec is pretty clear that ZSE to ZSF is a legal direct
transition. So I don't think the transition should be allowed to fail
due to a lack of resources.

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