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From: Coly Li <colyli@suse.de>
To: Damien Le Moal <Damien.LeMoal@wdc.com>,
	"linux-bcache@vger.kernel.org" <linux-bcache@vger.kernel.org>
Cc: Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"hare@suse.com" <hare@suse.com>
Subject: Re: [RFC PATCH v4 2/3] bcache: handle zone management bios for bcache device
Date: Tue, 2 Jun 2020 18:18:36 +0800
Message-ID: <e73f00de-f5d0-a8f7-e7a6-c3285fbfd368@suse.de> (raw)
In-Reply-To: <05e3dda28565c85f5beb0055a43ca4f685572431.camel@wdc.com>

On 2020/6/2 16:54, Damien Le Moal wrote:
> On Tue, 2020-06-02 at 00:06 +0800, Coly Li wrote:
>>>> +		 * cache device.
>>>> +		 */
>>>> +		if (bio_op(bio) == REQ_OP_ZONE_RESET_ALL)
>>>> +			nr_zones = s->d->disk->queue->nr_zones;
>>>
>>> Not: sending a REQ_OP_ZONE_RESET BIO to a conventional zone will be failed by
>>> the disk... This is not allowed by the ZBC/ZAC specs. So invalidation the cache
>>> for conventional zones is not really necessary. But as an initial support, I
>>> think this is fine. This can be optimized later.
>>>
>> Copied, will think of how to optimized later. So far in my testing,
>> resetting conventional zones may receive error and timeout from
>> underlying drivers and bcache code just forwards such error to upper
>> layer. What I see is the reset command hangs for a quite long time and
>> failed. I will find a way to make the zone reset command on conventional
>> zone fail immediately.
> 
> It is 100% guaranteed that a zone reset issued to a conventional zone
> will fail. That is defined in ZBC/ZAC specifications. Resetting a
> single conventional zone is an error. We know the command will fail and
> the failure is instantaneous from the drive. The scsi layer should not
> retry these failed reset zone command, we have special error handling
> code preventing retries since we know that the command can only fail
> again. So I am not sure why you are seeing hang/long time before the
> failure is signaled... This may need investigation.
> 
> 

Copied. Currently I plan to add a first_seq_zone_nr to bcache on-disk
super block, its value will be set by user space bcache-tools when the
backing device is formatted for bcache. Then the zone reset bio which
has smaller zone number will be rejected immediately by bcache code.

This requires on-disk format change, I will do it later with other
on-disk change stuffs.

Coly Li

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-22 12:18 [RFC PATCH v4 0/3] bcache: support zoned device as bcache backing device Coly Li
2020-05-22 12:18 ` [RFC PATCH v4 1/3] bcache: export bcache zone information for zoned " Coly Li
2020-05-25  1:10   ` Damien Le Moal
2020-06-01 12:34     ` Coly Li
2020-06-02  8:48       ` Damien Le Moal
2020-06-02 12:50         ` Coly Li
2020-06-03  0:58           ` Damien Le Moal
2020-05-22 12:18 ` [RFC PATCH v4 2/3] bcache: handle zone management bios for bcache device Coly Li
2020-05-25  1:24   ` Damien Le Moal
2020-06-01 16:06     ` Coly Li
2020-06-02  8:54       ` Damien Le Moal
2020-06-02 10:18         ` Coly Li [this message]
2020-06-03  0:51           ` Damien Le Moal
2020-05-22 12:18 ` [RFC PATCH v4 3/3] bcache: reject writeback cache mode for zoned backing device Coly Li
2020-05-25  1:26   ` Damien Le Moal
2020-06-01 16:09     ` Coly Li
2020-05-25  5:25 ` [RFC PATCH v4 0/3] bcache: support zoned device as bcache " Damien Le Moal
2020-05-25  8:14   ` Coly Li

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