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From: Damien Le Moal <Damien.LeMoal@wdc.com>
To: "hch@lst.de" <hch@lst.de>
Cc: "Javier González" <javier@javigon.com>,
	"Matias Bjørling" <mb@lightnvm.io>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"kbusch@kernel.org" <kbusch@kernel.org>,
	"sagi@grimberg.me" <sagi@grimberg.me>,
	"axboe@kernel.dk" <axboe@kernel.dk>,
	"SelvaKumar S" <selvakuma.s1@samsung.com>,
	"Kanchan Joshi" <joshi.k@samsung.com>,
	"Nitesh Shetty" <nj.shetty@samsung.com>
Subject: Re: [PATCH 3/6] block: add support for zone offline transition
Date: Fri, 26 Jun 2020 09:15:14 +0000	[thread overview]
Message-ID: <CY4PR04MB3751E3DF3A1BD1FC77E6C101E7930@CY4PR04MB3751.namprd04.prod.outlook.com> (raw)
In-Reply-To: 20200626091113.GB26616@lst.de

On 2020/06/26 18:11, hch@lst.de wrote:
> On Fri, Jun 26, 2020 at 01:14:30AM +0000, Damien Le Moal wrote:
>> As long as you keep ZNS namespace report itself as being "host-managed" like
>> ZBC/ZAC disks, we need the consistency and common interface. If you break that,
>> the meaning of the zoned model queue attribute disappears and an application or
>> in-kernel user cannot rely on this model anymore to know how the drive will behave.
> 
> We just need a way to expose to applications that new feature are
> supported.  Just like we did with zone capacity support.  That is why
> we added the feature flags to uapi zone structure.
> 
>> Think of a file system, or any other in-kernel user. If they have to change
>> their code based on the device type (NVMe vs SCSI), then the zoned block device
>> interface is broken. Right now, that is not the case, everything works equally
>> well on ZNS and SCSI, modulo the need by a user for conventional zones that ZNS
>> do not define. But that is still consistent with the host-managed model since
>> conventional zones are optional.
> 
> That is why we have the feature flag.  That user should not know the
> underlying transport or spec.  But it can reliably discover "this thing
> support zone capacity" or "this thing supports offline zones" or even
> nasty thing like "this zone can time out when open" which are much
> harder to deal with.
> 
>> For this particular patch, there is currently no in-kernel user, and it is not
>> clear how this will be useful to applications. At least please clarify this. And
> 
> The main user is the ioctl.  And if you think about how offline zones are
> (suppose to) be used driving this from management tools in userspace
> actually totally make sense.  Unlike for example open/close all which
> just don't make sense as primitives to start with.

OK. Adding a new BLKZONEOFFLINE ioctl is easy though and fits into the current
zone management plumbing well, I think. So the patch can be significantly
simplified (no need for the new zone management op function with flags).

> 


-- 
Damien Le Moal
Western Digital Research

  reply	other threads:[~2020-06-26  9:15 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-25 12:21 [PATCH 0/6] ZNS: Extra features for current patches Javier González
2020-06-25 12:21 ` [PATCH 1/6] block: introduce IOCTL for zone mgmt Javier González
2020-06-26  1:17   ` Damien Le Moal
2020-06-26  6:01     ` Javier González
2020-06-26  6:37       ` Damien Le Moal
2020-06-26  6:51         ` Javier González
2020-06-26  7:03           ` Damien Le Moal
2020-06-26  7:08             ` Javier González
2020-06-25 12:21 ` [PATCH 2/6] block: add support for selecting all zones Javier González
2020-06-26  1:27   ` Damien Le Moal
2020-06-26  5:58     ` Javier González
2020-06-26  6:35       ` Damien Le Moal
2020-06-26  6:52         ` Javier González
2020-06-26  7:06           ` Damien Le Moal
2020-06-25 12:21 ` [PATCH 3/6] block: add support for zone offline transition Javier González
2020-06-25 14:12   ` Matias Bjørling
2020-06-25 19:48     ` Javier González
2020-06-26  1:14       ` Damien Le Moal
2020-06-26  6:18         ` Javier González
2020-06-26  9:11         ` hch
2020-06-26  9:15           ` Damien Le Moal [this message]
2020-06-26  9:17             ` hch
2020-06-26 10:02               ` Javier González
2020-06-26  9:07     ` Christoph Hellwig
2020-06-26  1:34   ` Damien Le Moal
2020-06-26  6:08     ` Javier González
2020-06-26  6:42       ` Damien Le Moal
2020-06-26  6:58         ` Javier González
2020-06-26  7:17           ` Damien Le Moal
2020-06-26  7:26             ` Javier González
2020-06-25 12:21 ` [PATCH 4/6] block: introduce IOCTL to report dev properties Javier González
2020-06-25 13:10   ` Matias Bjørling
2020-06-25 19:42     ` Javier González
2020-06-25 19:58       ` Matias Bjørling
2020-06-26  6:24         ` Javier González
2020-06-25 20:25       ` Keith Busch
2020-06-26  6:28         ` Javier González
2020-06-26 15:52           ` Keith Busch
2020-06-26 16:25             ` Javier González
2020-06-26  0:57       ` Damien Le Moal
2020-06-26  6:27         ` Javier González
2020-06-26  1:38   ` Damien Le Moal
2020-06-26  6:22     ` Javier González
2020-06-25 12:21 ` [PATCH 5/6] block: add zone attr. to zone mgmt IOCTL struct Javier González
2020-06-25 15:13   ` Matias Bjørling
2020-06-25 19:51     ` Javier González
2020-06-26  1:45   ` Damien Le Moal
2020-06-26  6:03     ` Javier González
2020-06-26  6:38       ` Damien Le Moal
2020-06-26  6:49         ` Javier González
2020-06-26  9:14   ` Christoph Hellwig
2020-06-26 10:01     ` Javier González
2020-06-25 12:21 ` [PATCH 6/6] nvme: Add consistency check for zone count Javier González
2020-06-25 13:16   ` Matias Bjørling
2020-06-25 19:45     ` Javier González
2020-06-25 21:49   ` Keith Busch
2020-06-26  0:04     ` Damien Le Moal
2020-06-26  6:13       ` Javier González
2020-06-26  6:49         ` Damien Le Moal
2020-06-26  6:55           ` Javier González
2020-06-26  7:09             ` Damien Le Moal
2020-06-26  7:29               ` Javier González
2020-06-26  7:42                 ` Damien Le Moal
2020-06-26  9:16   ` Christoph Hellwig
2020-06-26 10:03     ` Javier González
2020-06-25 13:04 ` [PATCH 0/6] ZNS: Extra features for current patches Matias Bjørling
2020-06-25 14:48   ` Matias Bjørling
2020-06-25 19:39     ` Javier González
2020-06-25 19:53       ` Matias Bjørling
2020-06-26  6:26         ` Javier González

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