Re: [PATCH V2] fs: New zonefs file system

[Damien Le Moal <Damien.LeMoal@wdc.com>]

Luis,

On 2019/08/23 7:44, Luis Chamberlain wrote:
> On Tue, Aug 20, 2019 at 05:12:49PM +0900, Damien Le Moal wrote:
>> The aggregated conventional zone file can be used as a regular file.
>> Operations such as the following work.
>>
>> mkfs.ext4 /mnt/cnv/0
>> mount -o loop /mnt/cnv/0 /data
> 
> Should BLK_DEV_LOOP_MIN_COUNT be increased if this is enabled to
> a mich higher sensible default? Right now the default is 8. Also,
> can we infer this later dynamically so so this can grow at proper
> scale without having to have user interaction?

I am not sure if this is really necessary, though I am not against it. I added
this in the commit message as as an example, simply because it is a very easy
way to test that the aggregated conventional zone file is working correctly. The
tendency these days it for drives to have very little, if any at all,
conventional zones. Even if they do, using dm-linear to chunk conventional and
sequential spaces into different block devices is probably a much better way to
separate the 2 zone types into different usage patterns.

> 
> For now, I mean something like:
> 
> diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
> index 1bb8ec575352..22ba4803b075 100644
> --- a/drivers/block/Kconfig
> +++ b/drivers/block/Kconfig
> @@ -217,7 +217,8 @@ config BLK_DEV_LOOP
>  config BLK_DEV_LOOP_MIN_COUNT
>  	int "Number of loop devices to pre-create at init time"
>  	depends on BLK_DEV_LOOP
> -	default 8
> +	default 8 if !ZONEFS FILESYSTEM
> +	default 32 if ZONEFS FILESYSTEM
>  	help
>  	  Static number of loop devices to be unconditionally pre-created
>  	  at init time.

Since this is a simple fix, I think we could reserve it for later if the need
for this change increases due to zonefs ? The default value can also be
automatically inferred by counting the number of zoned disk in the system and
assuming one extra loop device for each zoned drive.

Best regards.

-- 
Damien Le Moal
Western Digital Research