linux-kernel - Re: [PATCH 04/13] ext4: remove gdb backup copy for meta bg in setup_new_flex_group

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Message-ID: <20230816031031.GL2247938@mit.edu>
Date:   Tue, 15 Aug 2023 23:10:31 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Kemeng Shi <shikemeng@...weicloud.com>
Cc:     adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/13] ext4: remove gdb backup copy for meta bg in
 setup_new_flex_group_blocks

On Thu, Jun 29, 2023 at 08:00:35PM +0800, Kemeng Shi wrote:
> Wrong check of gdb backup in meta bg as following:
> first_group is the first group of meta_bg which contains target group, so
> target group is always >= first_group. We check if target group has gdb
> backup by comparing first_group with [group + 1] and [group +
> EXT4_DESC_PER_BLOCK(sb) - 1]. As group >= first_group, then [group + N] is
> > first_group. So no copy of gdb backup in meta bg is done in
> setup_new_flex_group_blocks.
> 
> No need to do gdb backup copy in meta bg from setup_new_flex_group_blocks
> as we always copy updated gdb block to backups at end of
> ext4_flex_group_add as following:
> 
> ext4_flex_group_add
>   /* no gdb backup copy for meta bg any more */
>   setup_new_flex_group_blocks
> 
>   /* update current group number */
>   ext4_update_super
>     sbi->s_groups_count += flex_gd->count;
> 
>   /*
>    * if group in meta bg contains backup is added, the primary gdb block
>    * of the meta bg will be copy to backup in new added group here.
>    */
>   for (; gdb_num <= gdb_num_end; gdb_num++)
>     update_backups(...)
> 
> In summary, we can remove wrong gdb backup copy code in
> setup_new_flex_group_blocks.
> 
> Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>

Reviewed-by: Theodore Ts'o <tytso@....edu>