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Date:   Thu, 5 Dec 2019 08:21:44 +0100
From:   Johannes Thumshirn <jthumshirn@suse.de>
To:     Naohiro Aota <naohiro.aota@wdc.com>
Cc:     linux-btrfs@vger.kernel.org, David Sterba <dsterba@suse.com>,
        Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
        Nikolay Borisov <nborisov@suse.com>,
        Damien Le Moal <damien.lemoal@wdc.com>,
        Hannes Reinecke <hare@suse.com>,
        Anand Jain <anand.jain@oracle.com>,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v5 05/28] btrfs: disallow space_cache in HMZONED mode
Message-ID: <20191205072144.GA6051@Johanness-MacBook-Pro.local>
References: <20191204081735.852438-1-naohiro.aota@wdc.com>
 <20191204081735.852438-6-naohiro.aota@wdc.com>
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On Wed, Dec 04, 2019 at 05:17:12PM +0900, Naohiro Aota wrote:
[...]
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 616f5abec267..d411574298f4 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -442,8 +442,12 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
>  	cache_gen = btrfs_super_cache_generation(info->super_copy);
>  	if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
>  		btrfs_set_opt(info->mount_opt, FREE_SPACE_TREE);
> -	else if (cache_gen)
> -		btrfs_set_opt(info->mount_opt, SPACE_CACHE);
> +	else if (cache_gen) {
> +		if (btrfs_fs_incompat(info, HMZONED))
> +			WARN_ON(1);
> +		else
> +			btrfs_set_opt(info->mount_opt, SPACE_CACHE);
> +	}

I would probably write this as follows:
	else if (cache_gen)
		if (!WARN_ON(btrfs_fs_incompat(info, HMZONED)))
			btrfs_set_opt(info->mount_opt, SPACE_CACHE);