linux-ext4 - Re: [PATCH v2 8/9] ext4: make ext4_insert_delayed

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Date: Mon, 29 Apr 2024 12:06:59 +0200
From: Jan Kara <jack@...e.cz>
To: Zhang Yi <yi.zhang@...weicloud.com>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz,
	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 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--;

									Honza

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