linux-kernel - Re: [PATCH v2 2/3] quota: Replace all block number checking with helper function

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Date:   Fri, 23 Sep 2022 13:48:40 +0200
From:   Jan Kara <jack@...e.cz>
To:     Zhihao Cheng <chengzhihao1@...wei.com>
Cc:     jack@...e.com, tytso@....edu, brauner@...nel.org,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, yukuai3@...wei.com
Subject: Re: [PATCH v2 2/3] quota: Replace all block number checking with
 helper function

On Thu 22-09-22 21:04:00, Zhihao Cheng wrote:
> Cleanup all block checking places, replace them with helper function
> do_check_range().
> 
> Signed-off-by: Zhihao Cheng <chengzhihao1@...wei.com>
> ---
>  fs/quota/quota_tree.c | 28 ++++++++++++----------------
>  1 file changed, 12 insertions(+), 16 deletions(-)

Thanks for the fix! One comment below:

> diff --git a/fs/quota/quota_tree.c b/fs/quota/quota_tree.c
> index f89186b6db1d..47711e739ddb 100644
> --- a/fs/quota/quota_tree.c
> +++ b/fs/quota/quota_tree.c
> @@ -71,11 +71,12 @@ static ssize_t write_blk(struct qtree_mem_dqinfo *info, uint blk, char *buf)
>  	return ret;
>  }
>  
> -static inline int do_check_range(struct super_block *sb, uint val, uint max_val)
> +static inline int do_check_range(struct super_block *sb, uint val,
> +				 uint min_val, uint max_val)
>  {
> -	if (val >= max_val) {
> -		quota_error(sb, "Getting block too big (%u >= %u)",
> -			    val, max_val);
> +	if (val < min_val || val >= max_val) {
> +		quota_error(sb, "Getting block %u out of range %u-%u",
> +			    val, min_val, max_val);
>  		return -EUCLEAN;
>  	}

It is strange that do_check_range() checks min_val() with strict inequality
and max_val with non-strict one. That's off-by-one problem waiting to
happen when we forget about this detail. Probably make max_val
non-inclusive as well (the parameter max_val suggests the passed value is
the biggest valid one anyway).

								Honza

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