linux-kernel - Re: [PATCH] exfat: speed up iterate/lookup by fixing start point of traversing fat chain

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Date:   Thu, 18 Mar 2021 10:02:24 +0900
From:   Hyeongseok Kim <hyeongseok@...il.com>
To:     Sungjong Seo <sj1557.seo@...sung.com>, namjae.jeon@...sung.com
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] exfat: speed up iterate/lookup by fixing start point of
 traversing fat chain

On 3/18/21 1:07 AM, Sungjong Seo wrote:
>>   /*
>> - * return values:
>> - *   >= 0	: return dir entiry position with the name in dir
>> - *   -ENOENT	: entry with the name does not exist
>> - *   -EIO	: I/O error
>> + * @ei:         inode info of directory
>> + * @p_dir:      input as directory structure in which we search name
>> + *              if found, output as a cluster dir where the name exists
>> + *              if not found, not changed from input
>> + * @num_entries entry size of p_uniname
>> + * @return:
>> + *   >= 0:      dir entry position from output p_dir.dir
>> + *   -ENOENT:   entry with the name does not exist
>> + *   -EIO:      I/O error
>>    */
>>   int exfat_find_dir_entry(struct super_block *sb, struct exfat_inode_info
>> *ei,
>>   		struct exfat_chain *p_dir, struct exfat_uni_name *p_uniname,
>> @@ -925,14 +930,16 @@ int exfat_find_dir_entry(struct super_block *sb,
>> struct exfat_inode_info *ei,
> [snip]
>    			hint_stat->clu = p_dir->dir;
>>   			hint_stat->eidx = 0;
>> -			return (dentry - num_ext);
>> +
>> +			exfat_chain_dup(p_dir, &tmp_clu);
>> +			return dentry_in_cluster;
>>   		}
>>   	}
>>
>>   	hint_stat->clu = clu.dir;
>>   	hint_stat->eidx = dentry + 1;
>> -	return dentry - num_ext;
>> +
>> +	exfat_chain_dup(p_dir, &tmp_clu);
>> +	return dentry_in_cluster;
>>   }
> Changing the functionality of exfat find_dir_entry() will affect
> exfat_find() and exfat_lookup(), breaking the concept of ei->dir.dir
> which should have the starting cluster of its parent directory.
>
> Well, is there any missing patch related to exfat_find()?
> It would be nice to modify the caller of this function, exfat_find(),
> so that this change in functionality doesn't affect other functions.
>
> Thanks.
>
Whoops, it's a bug. I didn't catch that, thanks.
Maybe it could make exfat inode hash problem.
I wanted to reuse current function interface but, it would be better
to add an addtional parameter. I'll fix this in v2.