linux-ext4 - Re: [PATCH 2/2] ext4: use optimized mballoc scanning regardless of inode format

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Message-ID: <5877f412-003c-4893-bf6d-229957802eda@gmail.com>
Date: Sat, 10 Jan 2026 09:38:13 +0800
From: Zhang Yi <yizhang089@...il.com>
To: Jan Kara <jack@...e.cz>, Ted Tso <tytso@....edu>
Cc: linux-ext4@...r.kernel.org, Baokun Li <libaokun1@...wei.com>
Subject: Re: [PATCH 2/2] ext4: use optimized mballoc scanning regardless of
 inode format

On 1/9/2026 6:53 PM, Jan Kara wrote:
> Currently we don't used mballoc optimized scanning (using max free
> extent order and avg free extent order group lists) for inodes with
> indirect block based format. This is confusing for users and I don't see
> a good reason for that. Even with indirect block based inode format we
> can spend big amount of time searching for free blocks for large
> filesystems with fragmented free space. To add to the confusion before
> commit 077d0c2c78df ("ext4: make mb_optimize_scan performance mount
> option work with extents") optimized scanning was applied *only* to
> indirect block based inodes so that commit appears as a performance
> regression to some users. Just use optimized scanning whenever it is
> enabled by mount options.
> 
> Signed-off-by: Jan Kara <jack@...e.cz>

Makes sense to me.

Reviewed-by: Zhang Yi <yi.zhang@...wei.com>

> ---
>   fs/ext4/mballoc.c | 2 --
>   1 file changed, 2 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index f0e07bf11a93..cd98c472631e 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -1145,8 +1145,6 @@ static inline int should_optimize_scan(struct ext4_allocation_context *ac)
>   		return 0;
>   	if (ac->ac_criteria >= CR_GOAL_LEN_SLOW)
>   		return 0;
> -	if (!ext4_test_inode_flag(ac->ac_inode, EXT4_INODE_EXTENTS))
> -		return 0;
>   	return 1;
>   }
>