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From: Naohiro Aota <Naohiro.Aota@wdc.com>
To: "dsterba@suse.cz" <dsterba@suse.cz>
Cc: "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
	"David Sterba" <dsterba@suse.com>, "Chris Mason" <clm@fb.com>,
	"Josef Bacik" <josef@toxicpanda.com>, "Qu Wenruo" <wqu@suse.com>,
	"Nikolay Borisov" <nborisov@suse.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Hannes Reinecke" <hare@suse.com>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"Damien Le Moal" <Damien.LeMoal@wdc.com>,
	"Matias Bjørling" <mb@lightnvm.io>,
	"Johannes Thumshirn" <jthumshirn@suse.de>,
	"Bart Van Assche" <bvanassche@acm.org>
Subject: Re: [PATCH 09/19] btrfs: limit super block locations in HMZONED mode
Date: Tue, 18 Jun 2019 09:01:35 +0000
Message-ID: <SN6PR04MB523133E2B4DA6705F79A48FF8CEA0@SN6PR04MB5231.namprd04.prod.outlook.com> (raw)
In-Reply-To: <20190617225356.GJ19057@twin.jikos.cz>

On 2019/06/18 7:53, David Sterba wrote:
> On Fri, Jun 07, 2019 at 10:10:15PM +0900, Naohiro Aota wrote:
>> When in HMZONED mode, make sure that device super blocks are located in
>> randomly writable zones of zoned block devices. That is, do not write super
>> blocks in sequential write required zones of host-managed zoned block
>> devices as update would not be possible.
> 
> This could be explained in more detail. My understanding is that the 1st
> and 2nd copy superblocks is skipped at write time but the zone
> containing the superblocks is not excluded from allocations. Ie. regular
> data can appear in place where the superblocks would exist on
> non-hmzoned filesystem. Is that correct?

Correct. You can see regular data stored at usually SB location on HMZONED fs.

> The other option is to completely exclude the zone that contains the
> superblock copies.
> 
> primary sb			 64K
> 1st copy			 64M
> 2nd copy			256G
> 
> Depends on the drives, but I think the size of the random write zone
> will very often cover primary and 1st copy. So there's at least some
> backup copy.
> 
> The 2nd copy will be in the sequential-only zone, so the whole zone
> needs to be excluded in exclude_super_stripes. But it's not, so this
> means data can go there.  I think the zone should be left empty.
> 

I see. That's more safe for the older kernel/userland, right? By keeping that zone empty,
we can avoid old ones to mis-interpret data to be SB.

Alright, I will change the code to do so.

  reply index

Thread overview: 79+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-07 13:10 [PATCH v2 00/19] btrfs zoned block device support Naohiro Aota
2019-06-07 13:10 ` [PATCH 01/19] btrfs: introduce HMZONED feature flag Naohiro Aota
2019-06-07 13:10 ` [PATCH 02/19] btrfs: Get zone information of zoned block devices Naohiro Aota
2019-06-13 13:58   ` Josef Bacik
2019-06-18  6:04     ` Naohiro Aota
2019-06-13 13:58   ` Josef Bacik
2019-06-17 18:57   ` David Sterba
2019-06-18  6:42     ` Naohiro Aota
2019-06-27 15:11       ` David Sterba
2019-06-07 13:10 ` [PATCH 03/19] btrfs: Check and enable HMZONED mode Naohiro Aota
2019-06-13 13:57   ` Josef Bacik
2019-06-18  6:43     ` Naohiro Aota
2019-06-07 13:10 ` [PATCH 04/19] btrfs: disable fallocate in " Naohiro Aota
2019-06-07 13:10 ` [PATCH 05/19] btrfs: disable direct IO " Naohiro Aota
2019-06-13 14:00   ` Josef Bacik
2019-06-18  8:17     ` Naohiro Aota
2019-06-07 13:10 ` [PATCH 06/19] btrfs: align dev extent allocation to zone boundary Naohiro Aota
2019-06-07 13:10 ` [PATCH 07/19] btrfs: do sequential extent allocation in HMZONED mode Naohiro Aota
2019-06-13 14:07   ` Josef Bacik
2019-06-18  8:28     ` Naohiro Aota
2019-06-18 13:37       ` Josef Bacik
2019-06-17 22:30   ` David Sterba
2019-06-18  8:49     ` Naohiro Aota
2019-06-27 15:28       ` David Sterba
2019-06-07 13:10 ` [PATCH 08/19] btrfs: make unmirroed BGs readonly only if we have at least one writable BG Naohiro Aota
2019-06-13 14:09   ` Josef Bacik
2019-06-18  7:42     ` Naohiro Aota
2019-06-18 13:35       ` Josef Bacik
2019-06-07 13:10 ` [PATCH 09/19] btrfs: limit super block locations in HMZONED mode Naohiro Aota
2019-06-13 14:12   ` Josef Bacik
2019-06-18  8:51     ` Naohiro Aota
2019-06-17 22:53   ` David Sterba
2019-06-18  9:01     ` Naohiro Aota [this message]
2019-06-27 15:35       ` David Sterba
2019-06-28  3:55   ` Anand Jain
2019-06-28  6:39     ` Naohiro Aota
2019-06-28  6:52       ` Anand Jain
2019-06-07 13:10 ` [PATCH 10/19] btrfs: rename btrfs_map_bio() Naohiro Aota
2019-06-07 13:10 ` [PATCH 11/19] btrfs: introduce submit buffer Naohiro Aota
2019-06-13 14:14   ` Josef Bacik
2019-06-17  3:16     ` Damien Le Moal
2019-06-18  0:00       ` David Sterba
2019-06-18  4:04         ` Damien Le Moal
2019-06-18 13:33       ` Josef Bacik
2019-06-19 10:32         ` Damien Le Moal
2019-06-07 13:10 ` [PATCH 12/19] btrfs: expire submit buffer on timeout Naohiro Aota
2019-06-13 14:15   ` Josef Bacik
2019-06-17  3:19     ` Damien Le Moal
2019-06-07 13:10 ` [PATCH 13/19] btrfs: avoid sync IO prioritization on checksum in HMZONED mode Naohiro Aota
2019-06-13 14:17   ` Josef Bacik
2019-06-07 13:10 ` [PATCH 14/19] btrfs: redirty released extent buffers in sequential BGs Naohiro Aota
2019-06-13 14:24   ` Josef Bacik
2019-06-18  9:09     ` Naohiro Aota
2019-06-07 13:10 ` [PATCH 15/19] btrfs: reset zones of unused block groups Naohiro Aota
2019-06-07 13:10 ` [PATCH 16/19] btrfs: wait existing extents before truncating Naohiro Aota
2019-06-13 14:25   ` Josef Bacik
2019-06-07 13:10 ` [PATCH 17/19] btrfs: shrink delayed allocation size in HMZONED mode Naohiro Aota
2019-06-13 14:27   ` Josef Bacik
2019-06-07 13:10 ` [PATCH 18/19] btrfs: support dev-replace " Naohiro Aota
2019-06-13 14:33   ` Josef Bacik
2019-06-18  9:14     ` Naohiro Aota
2019-06-07 13:10 ` [PATCH 19/19] btrfs: enable to mount HMZONED incompat flag Naohiro Aota
2019-06-07 13:17 ` [PATCH 01/12] btrfs-progs: build: Check zoned block device support Naohiro Aota
2019-06-07 13:17   ` [PATCH 02/12] btrfs-progs: utils: Introduce queue_param Naohiro Aota
2019-06-07 13:17   ` [PATCH 03/12] btrfs-progs: add new HMZONED feature flag Naohiro Aota
2019-06-07 13:17   ` [PATCH 04/12] btrfs-progs: Introduce zone block device helper functions Naohiro Aota
2019-06-07 13:17   ` [PATCH 05/12] btrfs-progs: load and check zone information Naohiro Aota
2019-06-07 13:17   ` [PATCH 06/12] btrfs-progs: avoid writing super block to sequential zones Naohiro Aota
2019-06-07 13:17   ` [PATCH 07/12] btrfs-progs: support discarding zoned device Naohiro Aota
2019-06-07 13:17   ` [PATCH 08/12] btrfs-progs: volume: align chunk allocation to zones Naohiro Aota
2019-06-07 13:17   ` [PATCH 09/12] btrfs-progs: do sequential allocation Naohiro Aota
2019-06-07 13:17   ` [PATCH 10/12] btrfs-progs: mkfs: Zoned block device support Naohiro Aota
2019-06-07 13:17   ` [PATCH 11/12] btrfs-progs: device-add: support HMZONED device Naohiro Aota
2019-06-07 13:17   ` [PATCH 12/12] btrfs-progs: introduce support for dev-place " Naohiro Aota
2019-06-12 17:51 ` [PATCH v2 00/19] btrfs zoned block device support David Sterba
2019-06-13  4:59   ` Naohiro Aota
2019-06-13 13:46     ` David Sterba
2019-06-14  2:07       ` Naohiro Aota
2019-06-17  2:44       ` Damien Le Moal

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