From: Coly Li <colyli@suse.de>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-block@vger.kernel.org, damien.lemoal@wdc.com,
hare@suse.com, axboe@kernel.dk, linux-bcache@vger.kernel.org,
kbusch@kernel.org
Subject: Re: [RFC PATCH v2 3/4] block: remove queue_is_mq restriction from blk_revalidate_disk_zones()
Date: Sat, 16 May 2020 21:13:50 +0800 [thread overview]
Message-ID: <d3fe49f1-d37b-689e-ae0e-078b1254d7e7@suse.de> (raw)
In-Reply-To: <20200516124020.GC13448@lst.de>
On 2020/5/16 20:40, Christoph Hellwig wrote:
> On Sat, May 16, 2020 at 11:54:33AM +0800, Coly Li wrote:
>> The bcache driver is bio based and NOT request based multiqueued driver,
>> if a zoned SMR hard drive is used as backing device of a bcache device,
>> calling blk_revalidate_disk_zones() for the bcache device will fail due
>> to the following check in blk_revalidate_disk_zones(),
>> 478 if (WARN_ON_ONCE(!queue_is_mq(q)))
>> 479 return -EIO;
>>
>> Now bcache is able to export the zoned information from the underlying
>> zoned SMR drives and format zonefs on top of a bcache device, the
>> resitriction that a zoned device should be multiqueued is unnecessary
>> for now.
>>
>> Although in commit ae58954d8734c ("block: don't handle bio based drivers
>> in blk_revalidate_disk_zones") it is said that bio based drivers should
>> not call blk_revalidate_disk_zones() and just manually update their own
>> q->nr_zones, but this is inaccurate. The bio based drivers also need to
>> set their zone size and initialize bitmaps for cnv and seq zones, it is
>> necessary to call blk_revalidate_disk_zones() for bio based drivers.
>
> Why would you need these bitmaps for bcache? There is no reason to
> serialize requests for stacking drivers, and you can already derive
> if a zone is sequential or not from whatever internal information
> you use.
>
> So without a user that actually makes sense: NAK.
>
It is OK for me to set the zone_nr and zone size without calling
blk_revalidate_disk_zones().
Coly Li
next prev parent reply other threads:[~2020-05-16 13:13 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-16 3:54 [RFC PATCH v2 0/4] block layer change necessary for bcache zoned device support Coly Li
2020-05-16 3:54 ` [RFC PATCH v2 1/4] block: change REQ_OP_ZONE_RESET from 6 to 13 Coly Li
2020-05-16 4:06 ` Chaitanya Kulkarni
2020-05-16 9:33 ` Coly Li
2020-05-16 12:38 ` Christoph Hellwig
2020-05-16 12:44 ` Coly Li
2020-05-16 12:50 ` Christoph Hellwig
2020-05-16 13:05 ` Coly Li
2020-05-16 15:36 ` Christoph Hellwig
2020-05-17 5:30 ` Coly Li
2020-05-18 6:53 ` Hannes Reinecke
2020-05-18 6:56 ` Damien Le Moal
2020-05-18 0:33 ` Damien Le Moal
2020-05-18 5:09 ` Chaitanya Kulkarni
2020-05-16 3:54 ` [RFC PATCH v2 2/4] block: block: change REQ_OP_ZONE_RESET_ALL from 8 to 15 Coly Li
2020-05-18 0:36 ` Damien Le Moal
2020-05-16 3:54 ` [RFC PATCH v2 3/4] block: remove queue_is_mq restriction from blk_revalidate_disk_zones() Coly Li
2020-05-16 12:40 ` Christoph Hellwig
2020-05-16 13:13 ` Coly Li [this message]
2020-05-16 15:35 ` Christoph Hellwig
2020-05-18 1:07 ` Damien Le Moal
2020-05-18 0:39 ` Damien Le Moal
2020-05-16 3:54 ` [RFC PATCH v2 4/4] block: set bi_size to REQ_OP_ZONE_RESET bio Coly Li
2020-05-16 12:53 ` Christoph Hellwig
2020-05-18 0:59 ` Damien Le Moal
2020-05-18 2:32 ` Coly Li
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