linux-kernel - Re: [PATCH 4/4] ext4: reduce unnecessary memory allocation in alloc_flex

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Message-ID: <20231019115719.54wd6q6dxanaodid@quack3>
Date:   Thu, 19 Oct 2023 13:57:19 +0200
From:   Jan Kara <jack@...e.cz>
To:     Baokun Li <libaokun1@...wei.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, jack@...e.cz, ritesh.list@...il.com,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
        yangerkun@...wei.com, yukuai3@...wei.com
Subject: Re: [PATCH 4/4] ext4: reduce unnecessary memory allocation in
 alloc_flex_gd()

On Wed 18-10-23 19:42:21, Baokun Li wrote:
> When a large flex_bg file system is resized, the number of groups to be
> added may be small, and a large amount of memory that will not be used will
> be allocated. Therefore, resize_bg can be set to the size after the number
> of new_group_data to be used is aligned upwards to the power of 2. This
> does not affect the disk layout after online resize and saves some memory.
> 
> Signed-off-by: Baokun Li <libaokun1@...wei.com>

Looks good, just one small comment below. Feel free to add:

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


> @@ -248,6 +250,14 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size)
>  	else
>  		flex_gd->resize_bg = flexbg_size;
>  
> +	/* Avoid allocating new groups that will not be used. */

Perhaps make the comment more understandable like:
	/* Avoid allocating large 'groups' array if not needed */

									Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR