Re: [PATCH 06/26] block: Introduce zone write plugging

Damien Le Moal
2024-02-05T05:37:44Z

On 2/5/24 14:11, Christoph Hellwig wrote:
> On Mon, Feb 05, 2024 at 11:41:04AM +0900, Damien Le Moal wrote:
>>> I think only queue re-configuration(blk_revalidate_zone) requires the
>>> queue usage counter. Otherwise, bdev open()/close() should work just
>>> fine.
>>
>> I want to check FS case though. No clear if mounting FS that supports zone
>> (btrfs) also uses bdev open ?
>
> Every file system opens the block device. But we don't just need the
> block device to be open, but we also need the block limits to not
> change, and the only way to do that is to hold a q_usage_counter
> reference.

OK. So I think that Hannes'idea to get/put the queue usage counter reference
based on a zone BIO plug becoming not empty (get ref) and becoming empty (put
ref) may be simpler then. And that would also work in the same way for blk-mq
and BIO based drivers.

--
Damien Le Moal
Western Digital Research