Re: [f2fs-dev] [PATCH 3/4] f2fs: use find_next_bit_le rather than test_bit_le in, find_in_block

[Gu Zheng <guz.fnst@cn.fujitsu.com>]

Hi Yu,
On 06/25/2014 10:30 AM, Chao Yu wrote:

> Hi Gu,
> 
> Just one nitpick.
> 
>> -----Original Message-----
>> From: Gu Zheng [mailto:guz.fnst@cn.fujitsu.com]
>> Sent: Tuesday, June 24, 2014 6:21 PM
>> To: Jaegeuk Kim
>> Cc: fsdevel; f2fs
>> Subject: [f2fs-dev] [PATCH 3/4] f2fs: use find_next_bit_le rather than test_bit_le in,
>> find_in_block
>>
>> Use find_next_bit_le rather than test_bit_le to improve search speed
>> lightly.
>>
>> Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
>> ---
>>  fs/f2fs/dir.c |   43 +++++++++++++++++++++----------------------
>>  1 files changed, 21 insertions(+), 22 deletions(-)
>>
>> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
>> index 3edd561..ba510fb 100644
>> --- a/fs/f2fs/dir.c
>> +++ b/fs/f2fs/dir.c
>> @@ -93,42 +93,41 @@ static struct f2fs_dir_entry *find_in_block(struct page *dentry_page,
>>  			const char *name, size_t namelen, int *max_slots,
>>  			f2fs_hash_t namehash, struct page **res_page)
>>  {
>> -	struct f2fs_dir_entry *de;
>> -	unsigned long bit_pos = 0;
>> +	unsigned long bit_pos = 0, bit_start = 0;
>>  	struct f2fs_dentry_block *dentry_blk = kmap(dentry_page);
>>  	const void *dentry_bits = &dentry_blk->dentry_bitmap;
>> -	int max_len = 0;
>>
>> -	while (bit_pos < NR_DENTRY_IN_BLOCK) {
>> -		if (!test_bit_le(bit_pos, dentry_bits)) {
>> -			if (bit_pos == 0)
>> -				max_len = 1;
>> -			else if (!test_bit_le(bit_pos - 1, dentry_bits))
>> -				max_len++;
>> -			bit_pos++;
>> -			continue;
>> +	while (bit_start < NR_DENTRY_IN_BLOCK) {
>> +		struct f2fs_dir_entry *de;
>> +		int max_len = 0;
>> +
>> +		bit_pos = find_next_bit_le(dentry_bits,
>> +					NR_DENTRY_IN_BLOCK, bit_start);
>> +
>> +		max_len = bit_pos - bit_start;
>> +		if (max_len > *max_slots) {
>> +			*max_slots = max_len;
>> +			max_len = 0;
> 
> It could be removed here, and also do not need to initialize above.

Nice catch, thanks.;)

Regards,
Gu

> 
> Thanks.
> Yu
> 
>>  		}
>> +
>> +		if (bit_pos >= NR_DENTRY_IN_BLOCK)
>> +			break;
>> +
>>  		de = &dentry_blk->dentry[bit_pos];
>>  		if (early_match_name(name, namelen, namehash, de)) {
>>  			if (!memcmp(dentry_blk->filename[bit_pos],
>>  							name, namelen)) {
>>  				*res_page = dentry_page;
>> -				goto found;
>> +				return de;
>>  			}
>>  		}
>> -		if (max_len > *max_slots) {
>> -			*max_slots = max_len;
>> -			max_len = 0;
>> -		}
>> -		bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
>> +
>> +		bit_start = bit_pos
>> +				+ GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
>>  	}
>>
>> -	de = NULL;
>>  	kunmap(dentry_page);
>> -found:
>> -	if (max_len > *max_slots)
>> -		*max_slots = max_len;
>> -	return de;
>> +	return NULL;
>>  }
>>
>>  static struct f2fs_dir_entry *find_in_level(struct inode *dir,
>> --
>> 1.7.7
>>
>>
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> 
> .
>