Date: Mon, 29 Apr 2024 20:54:17 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: Jan Kara <jack@...e.cz>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, tytso@....edu,
 adilger.kernel@...ger.ca, yi.zhang@...wei.com, chengzhihao1@...wei.com,
 yukuai3@...wei.com
Subject: Re: [PATCH v2 8/9] ext4: make ext4_insert_delayed_block() insert
 multi-blocks

On 2024/4/29 18:06, Jan Kara wrote:
> On Wed 10-04-24 11:42:02, Zhang Yi wrote:
>> From: Zhang Yi <yi.zhang@...wei.com>
>>
>> Rename ext4_insert_delayed_block() to ext4_insert_delayed_blocks(),
>> pass length parameter to make it insert multi delalloc blocks once a
>> time. For non-bigalloc case, just reserve len blocks and insert delalloc
>> extent. For bigalloc case, we can ensure the middle clusters are not
>> allocated, but need to check whether the start and end clusters are
>> delayed/allocated, if not, we should reserve more space for the start
>> and/or end block(s).
>>
>> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
> 
> Thanks for the patch. Some comments below.
> 
>> ---
>>  fs/ext4/inode.c | 51 ++++++++++++++++++++++++++++++++++---------------
>>  1 file changed, 36 insertions(+), 15 deletions(-)
>>
>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>> index 46c34baa848a..08e2692b7286 100644
>> --- a/fs/ext4/inode.c
>> +++ b/fs/ext4/inode.c
>> @@ -1678,24 +1678,28 @@ static int ext4_da_check_clu_allocated(struct inode *inode, ext4_lblk_t lblk,
>>  }
>>  
>>  /*
>> - * ext4_insert_delayed_block - adds a delayed block to the extents status
>> - *                             tree, incrementing the reserved cluster/block
>> - *                             count or making a pending reservation
>> - *                             where needed
>> + * ext4_insert_delayed_blocks - adds a multiple delayed blocks to the extents
>> + *                              status tree, incrementing the reserved
>> + *                              cluster/block count or making pending
>> + *                              reservations where needed
>>   *
>>   * @inode - file containing the newly added block
>> - * @lblk - logical block to be added
>> + * @lblk - start logical block to be added
>> + * @len - length of blocks to be added
>>   *
>>   * Returns 0 on success, negative error code on failure.
>>   */
>> -static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk)
>> +static int ext4_insert_delayed_blocks(struct inode *inode, ext4_lblk_t lblk,
>> +				      ext4_lblk_t len)
>>  {
>>  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
>> -	int ret;
>> -	bool allocated = false;
>> +	int resv_clu, ret;
> 	    ^^^ this variable is in prinple the length of the extent. Thus
> it should be ext4_lblk_t type.
> 
>> +	bool lclu_allocated = false;
>> +	bool end_allocated = false;
>> +	ext4_lblk_t end = lblk + len - 1;
>>  
>>  	/*
>> -	 * If the cluster containing lblk is shared with a delayed,
>> +	 * If the cluster containing lblk or end is shared with a delayed,
>>  	 * written, or unwritten extent in a bigalloc file system, it's
>>  	 * already been accounted for and does not need to be reserved.
>>  	 * A pending reservation must be made for the cluster if it's
>> @@ -1706,21 +1710,38 @@ static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk)
>>  	 * extents status tree doesn't get a match.
>>  	 */
>>  	if (sbi->s_cluster_ratio == 1) {
>> -		ret = ext4_da_reserve_space(inode, 1);
>> +		ret = ext4_da_reserve_space(inode, len);
>>  		if (ret != 0)   /* ENOSPC */
>>  			return ret;
>>  	} else {   /* bigalloc */
>> -		ret = ext4_da_check_clu_allocated(inode, lblk, &allocated);
>> +		resv_clu = EXT4_B2C(sbi, end) - EXT4_B2C(sbi, lblk) - 1;
>> +		if (resv_clu < 0)
>> +			resv_clu = 0;
> 
> Here resv_clu going negative is strange I'm not sure the math is 100%
> correct in all the cases. I think it would be more logical as:
> 
> 		resv_clu = EXT4_B2C(sbi, end) - EXT4_B2C(sbi, lblk) + 1;
>> and then update resv_clu below as:
> 
>> +
>> +		ret = ext4_da_check_clu_allocated(inode, lblk, &lclu_allocated);
>>  		if (ret < 0)
>>  			return ret;
>> -		if (ret > 0) {
>> -			ret = ext4_da_reserve_space(inode, 1);
>> +		if (ret > 0)
>> +			resv_clu++;
> 
> Here we would do:
> 		if (ret == 0)
> 			resv_clu--;
> 
>> +
>> +		if (EXT4_B2C(sbi, lblk) != EXT4_B2C(sbi, end)) {
>> +			ret = ext4_da_check_clu_allocated(inode, end,
>> +							  &end_allocated);
>> +			if (ret < 0)
>> +				return ret;
>> +			if (ret > 0)
>> +				resv_clu++;
> 
> And similarly here:
> 			if (ret == 0)
> 				resv_clu--;

Oh, yes, it is definitely more logical than mine. Thanks for taking time
to review this series, other changelog and comments suggestions in this
series are looks fine to me, I will use them. Besides, Ritesh improved
my changelog in patch 2, I will keep your reviewed tag if you don't have
different opinions.

Thanks,
Yi.

> 
>> +		}
>> +
>> +		if (resv_clu) {
>> +			ret = ext4_da_reserve_space(inode, resv_clu);
>>  			if (ret != 0)   /* ENOSPC */
>>  				return ret;
>>  		}
>>  	}
>>  
>> -	ext4_es_insert_delayed_extent(inode, lblk, 1, allocated, false);
>> +	ext4_es_insert_delayed_extent(inode, lblk, len, lclu_allocated,
>> +				      end_allocated);
>>  	return 0;
>>  }
>>  
>> @@ -1823,7 +1844,7 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
>>  		}
>>  	}
>>  
>> -	retval = ext4_insert_delayed_block(inode, map->m_lblk);
>> +	retval = ext4_insert_delayed_blocks(inode, map->m_lblk, map->m_len);
>>  	up_write(&EXT4_I(inode)->i_data_sem);
>>  	if (retval)
>>  		return retval;
>> -- 
>> 2.39.2
>>

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