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Date: Wed, 17 Jan 2024 13:56:47 +0100
From: Jan Kara <jack@suse.cz>
To: yangerkun <yangerkun@huawei.com>
Cc: tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.cz,
	linux-ext4@vger.kernel.org, yangerkun@huaweicloud.com
Subject: Re: [PATCH 1/2] ext4: remove unused buddy_loaded in
 ext4_mb_seq_groups_show
Message-ID: <20240117125647.4gyqfhngii2dxnlo@quack3>
References: <20240117115223.80253-1-yangerkun@huawei.com>
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In-Reply-To: <20240117115223.80253-1-yangerkun@huawei.com>

On Wed 17-01-24 19:52:22, yangerkun wrote:
> We can just first call ext4_mb_unload_buddy, then copy information from
> ext4_group_info. So remove this unused value.
> 
> Signed-off-by: yangerkun <yangerkun@huawei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

Although I'd prefer if you add a comment before memcpy() like:

	/*
	 * We care only about free space counters in the group info and
	 * these are safe to access even after the buddy has been unloaded
	 */

								Honza

> ---
>  fs/ext4/mballoc.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index f44f668e407f..139f232bdbb5 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2990,8 +2990,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
>  {
>  	struct super_block *sb = pde_data(file_inode(seq->file));
>  	ext4_group_t group = (ext4_group_t) ((unsigned long) v);
> -	int i;
> -	int err, buddy_loaded = 0;
> +	int i, err;
>  	struct ext4_buddy e4b;
>  	struct ext4_group_info *grinfo;
>  	unsigned char blocksize_bits = min_t(unsigned char,
> @@ -3021,14 +3020,10 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
>  			seq_printf(seq, "#%-5u: I/O error\n", group);
>  			return 0;
>  		}
> -		buddy_loaded = 1;
> +		ext4_mb_unload_buddy(&e4b);
>  	}
>  
>  	memcpy(&sg, grinfo, i);
> -
> -	if (buddy_loaded)
> -		ext4_mb_unload_buddy(&e4b);
> -
>  	seq_printf(seq, "#%-5u: %-5u %-5u %-5u [", group, sg.info.bb_free,
>  			sg.info.bb_fragments, sg.info.bb_first_free);
>  	for (i = 0; i <= 13; i++)
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR