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

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Message-ID: <4dcff9fa-af8e-52bb-536a-26a2c6fa8bbf@huawei.com>
Date:   Thu, 19 Oct 2023 20:03:39 +0800
From:   Baokun Li <libaokun1@...wei.com>
To:     Jan Kara <jack@...e.cz>
CC:     <linux-ext4@...r.kernel.org>, <tytso@....edu>,
        <adilger.kernel@...ger.ca>, <ritesh.list@...il.com>,
        <linux-kernel@...r.kernel.org>, <yi.zhang@...wei.com>,
        <yangerkun@...wei.com>, <yukuai3@...wei.com>,
        Baokun Li <libaokun1@...wei.com>
Subject: Re: [PATCH 4/4] ext4: reduce unnecessary memory allocation in
 alloc_flex_gd()

On 2023/10/19 19:57, Jan Kara wrote:
> 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
Thank you very much for your careful review!
I'll change the comment to this more understandable one in the next version.

Cheers!
-- 
With Best Regards,
Baokun Li
.