Re: [PATCH v2 5/9] ext4: add new attr pointer attr_mb_order

[Jan Kara]

On Tue 27-02-24 17:11:44, Baokun Li wrote:
> The s_mb_best_avail_max_trim_order is of type unsigned int, and has a
> range of values well beyond the normal use of the mb_order. Although the
> mballoc code is careful enough that large numbers don't matter there, but
> this can mislead the sysadmin into thinking that it's normal to set such
> values. Hence add a new attr_id attr_mb_order with values in the range
> [0, 64] to avoid storing garbage values and make us more resilient to
> surprises in the future.
> 
> Suggested-by: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

								Honza

> ---
>  fs/ext4/sysfs.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
> index ddd71673176c..8e0473169458 100644
> --- a/fs/ext4/sysfs.c
> +++ b/fs/ext4/sysfs.c
> @@ -30,6 +30,7 @@ typedef enum {
>  	attr_first_error_time,
>  	attr_last_error_time,
>  	attr_clusters_in_group,
> +	attr_mb_order,
>  	attr_feature,
>  	attr_pointer_ui,
>  	attr_pointer_ul,
> @@ -210,6 +211,8 @@ EXT4_ATTR_OFFSET(inode_readahead_blks, 0644, inode_readahead,
>  		 ext4_sb_info, s_inode_readahead_blks);
>  EXT4_ATTR_OFFSET(mb_group_prealloc, 0644, clusters_in_group,
>  		 ext4_sb_info, s_mb_group_prealloc);
> +EXT4_ATTR_OFFSET(mb_best_avail_max_trim_order, 0644, mb_order,
> +		 ext4_sb_info, s_mb_best_avail_max_trim_order);
>  EXT4_RW_ATTR_SBI_UI(inode_goal, s_inode_goal);
>  EXT4_RW_ATTR_SBI_UI(mb_stats, s_mb_stats);
>  EXT4_RW_ATTR_SBI_UI(mb_max_to_scan, s_mb_max_to_scan);
> @@ -225,7 +228,6 @@ EXT4_RW_ATTR_SBI_UI(warning_ratelimit_interval_ms, s_warning_ratelimit_state.int
>  EXT4_RW_ATTR_SBI_UI(warning_ratelimit_burst, s_warning_ratelimit_state.burst);
>  EXT4_RW_ATTR_SBI_UI(msg_ratelimit_interval_ms, s_msg_ratelimit_state.interval);
>  EXT4_RW_ATTR_SBI_UI(msg_ratelimit_burst, s_msg_ratelimit_state.burst);
> -EXT4_RW_ATTR_SBI_UI(mb_best_avail_max_trim_order, s_mb_best_avail_max_trim_order);
>  #ifdef CONFIG_EXT4_DEBUG
>  EXT4_RW_ATTR_SBI_UL(simulate_fail, s_simulate_fail);
>  #endif
> @@ -379,6 +381,7 @@ static ssize_t ext4_generic_attr_show(struct ext4_attr *a,
>  	switch (a->attr_id) {
>  	case attr_inode_readahead:
>  	case attr_clusters_in_group:
> +	case attr_mb_order:
>  	case attr_pointer_ui:
>  		if (a->attr_ptr == ptr_ext4_super_block_offset)
>  			return sysfs_emit(buf, "%u\n", le32_to_cpup(ptr));
> @@ -458,6 +461,14 @@ static ssize_t ext4_generic_attr_store(struct ext4_attr *a,
>  		else
>  			*((unsigned int *) ptr) = t;
>  		return len;
> +	case attr_mb_order:
> +		ret = kstrtouint(skip_spaces(buf), 0, &t);
> +		if (ret)
> +			return ret;
> +		if (t > 64)
> +			return -EINVAL;
> +		*((unsigned int *) ptr) = t;
> +		return len;
>  	case attr_clusters_in_group:
>  		ret = kstrtouint(skip_spaces(buf), 0, &t);
>  		if (ret)
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR