Re: [PATCH v5 09/28] btrfs: align device extent allocation to zone boundary

[Johannes Thumshirn <jthumshirn@suse.de>]

On Wed, Dec 04, 2019 at 05:17:16PM +0900, Naohiro Aota wrote:
[...]

Only commenting on the code, not the design, sorry. I'll leave that to someone
with more experience in BTRFS.

>  	 * at an offset of at least 1MB.
>  	 */
>  	search_start = max_t(u64, search_start, SZ_1M);
> +	/*
> +	 * For a zoned block device, skip the first zone of the device
> +	 * entirely.
> +	 */
> +	if (device->zone_info)
> +		zone_size = device->zone_info->zone_size;
> +	search_start = max_t(u64, search_start, zone_size);
> +	search_start = btrfs_zone_align(device, search_start);

	if (device->zone_info) {
		zone_size = device->zone_info->zone_size;
		search_start = max_t(u64, search_start, zone_size);
		search_start = btrfs_zone_align(device, search_start);
	}

That's the equivalent code, but should make it a bit more clear what's
happening int the HMZONED and !HMZOED cases.

And I /guess/ we're saving some cycles in the !HMZONED case as we don't have
to adjust search start there.

[...]

> @@ -4778,6 +4805,7 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
>  	int i;
>  	int j;
>  	int index;
> +	int hmzoned = btrfs_fs_incompat(info, HMZONED);

	bool hmzoned = btrfs_fs_incompat(info, HMZONED);