linux-ext4 - Re: [PATCH 1/2] ext4: always allocate blocks only from groups inode can use

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Message-ID: <672568c5-0f5f-4e94-bfc3-45cf6135e47e@gmail.com>
Date: Sat, 10 Jan 2026 09:36:49 +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 1/2] ext4: always allocate blocks only from groups inode
 can use

On 1/9/2026 6:53 PM, Jan Kara wrote:
> For filesystems with more than 2^32 blocks inodes using indirect block
> based format cannot use blocks beyond the 32-bit limit.
> ext4_mb_scan_groups_linear() takes care to not select these unsupported
> groups for such inodes however other functions selecting groups for
> allocation don't. So far this is harmless because the other selection
> functions are used only with mb_optimize_scan and this is currently
> disabled for inodes with indirect blocks however in the following patch
> we want to enable mb_optimize_scan regardless of inode format.
> 
> Signed-off-by: Jan Kara <jack@...e.cz>

Looks good to me.

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

> ---
>   fs/ext4/mballoc.c | 26 +++++++++++++++++---------
>   1 file changed, 17 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 56d50fd3310b..f0e07bf11a93 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -892,6 +892,18 @@ mb_update_avg_fragment_size(struct super_block *sb, struct ext4_group_info *grp)
>   	}
>   }
>   
> +static ext4_group_t ext4_get_allocation_groups_count(
> +				struct ext4_allocation_context *ac)
> +{
> +	ext4_group_t ngroups = ext4_get_groups_count(ac->ac_sb);
> +
> +	/* non-extent files are limited to low blocks/groups */
> +	if (!(ext4_test_inode_flag(ac->ac_inode, EXT4_INODE_EXTENTS)))
> +		ngroups = EXT4_SB(ac->ac_sb)->s_blockfile_groups;
> +
> +	return ngroups;
> +}
> +
>   static int ext4_mb_scan_groups_xa_range(struct ext4_allocation_context *ac,
>   					struct xarray *xa,
>   					ext4_group_t start, ext4_group_t end)
> @@ -899,7 +911,7 @@ static int ext4_mb_scan_groups_xa_range(struct ext4_allocation_context *ac,
>   	struct super_block *sb = ac->ac_sb;
>   	struct ext4_sb_info *sbi = EXT4_SB(sb);
>   	enum criteria cr = ac->ac_criteria;
> -	ext4_group_t ngroups = ext4_get_groups_count(sb);
> +	ext4_group_t ngroups = ext4_get_allocation_groups_count(ac);
>   	unsigned long group = start;
>   	struct ext4_group_info *grp;
>   
> @@ -951,7 +963,7 @@ static int ext4_mb_scan_groups_p2_aligned(struct ext4_allocation_context *ac,
>   	ext4_group_t start, end;
>   
>   	start = group;
> -	end = ext4_get_groups_count(ac->ac_sb);
> +	end = ext4_get_allocation_groups_count(ac);
>   wrap_around:
>   	for (i = ac->ac_2order; i < MB_NUM_ORDERS(ac->ac_sb); i++) {
>   		ret = ext4_mb_scan_groups_largest_free_order_range(ac, i,
> @@ -1001,7 +1013,7 @@ static int ext4_mb_scan_groups_goal_fast(struct ext4_allocation_context *ac,
>   	ext4_group_t start, end;
>   
>   	start = group;
> -	end = ext4_get_groups_count(ac->ac_sb);
> +	end = ext4_get_allocation_groups_count(ac);
>   wrap_around:
>   	i = mb_avg_fragment_size_order(ac->ac_sb, ac->ac_g_ex.fe_len);
>   	for (; i < MB_NUM_ORDERS(ac->ac_sb); i++) {
> @@ -1083,7 +1095,7 @@ static int ext4_mb_scan_groups_best_avail(struct ext4_allocation_context *ac,
>   		min_order = fls(ac->ac_o_ex.fe_len);
>   
>   	start = group;
> -	end = ext4_get_groups_count(ac->ac_sb);
> +	end = ext4_get_allocation_groups_count(ac);
>   wrap_around:
>   	for (i = order; i >= min_order; i--) {
>   		int frag_order;
> @@ -1182,11 +1194,7 @@ static int ext4_mb_scan_groups(struct ext4_allocation_context *ac)
>   	int ret = 0;
>   	ext4_group_t start;
>   	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
> -	ext4_group_t ngroups = ext4_get_groups_count(ac->ac_sb);
> -
> -	/* non-extent files are limited to low blocks/groups */
> -	if (!(ext4_test_inode_flag(ac->ac_inode, EXT4_INODE_EXTENTS)))
> -		ngroups = sbi->s_blockfile_groups;
> +	ext4_group_t ngroups = ext4_get_allocation_groups_count(ac);
>   
>   	/* searching for the right group start from the goal value specified */
>   	start = ac->ac_g_ex.fe_group;