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Date:   Thu, 3 Dec 2020 10:08:41 -0500
From:   "Theodore Y. Ts'o" <tytso@mit.edu>
To:     Chunguang Xu <brookxu.cn@gmail.com>
Cc:     adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org
Subject: Re: [PATCH RESEND 4/8] ext4: add the gdt block of meta_bg to
 system_zone
Message-ID: <20201203150841.GM441757@mit.edu>
References: <1604764698-4269-1-git-send-email-brookxu@tencent.com>
 <1604764698-4269-4-git-send-email-brookxu@tencent.com>
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On Sat, Nov 07, 2020 at 11:58:14PM +0800, Chunguang Xu wrote:
> From: Chunguang Xu <brookxu@tencent.com>
> 
> In order to avoid poor search efficiency of system_zone, the
> system only adds metadata of some sparse group to system_zone.
> In the meta_bg scenario, the non-sparse group may contain gdt
> blocks. Perhaps we should add these blocks to system_zone to
> improve fault tolerance without significantly reducing system
> performance.

> @@ -226,13 +227,16 @@ int ext4_setup_system_zone(struct super_block *sb)
>  
>  	for (i=0; i < ngroups; i++) {
>  		cond_resched();
> -		if (ext4_bg_has_super(sb, i) &&
> -		    ((i < 5) || ((i % flex_size) == 0))) {
> -			ret = add_system_zone(system_blks,
> -					ext4_group_first_block_no(sb, i),
> -					ext4_bg_num_gdb(sb, i) + 1, 0);
> -			if (ret)
> -				goto err;
> +		if ((i < 5) || ((i % flex_size) == 0)) {

If we're going to do this, why not just drop the above conditional,
and just always do this logic for all block groups?

> +			gd_blks = ext4_bg_has_super(sb, i) +
> +				ext4_bg_num_gdb(sb, i);
> +			if (gd_blks) {
> +				ret = add_system_zone(system_blks,
> +						ext4_group_first_block_no(sb, i),
> +						gd_blks, 0);
> +				if (ret)
> +					goto err;
> +			}

						- Ted