linux-ext4 - Re: [PATCH v3 08/10] ext4: factor out check for whether a cluster is allocated

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Date: Sun, 12 May 2024 17:40:37 +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,
	linux-kernel@...r.kernel.org, tytso@....edu,
	adilger.kernel@...ger.ca, jack@...e.cz, ritesh.list@...il.com,
	yi.zhang@...wei.com, chengzhihao1@...wei.com, yukuai3@...wei.com
Subject: Re: [PATCH v3 08/10] ext4: factor out check for whether a cluster is
 allocated

On Wed 08-05-24 14:12:18, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
> 
> Factor out a common helper ext4_da_check_clu_allocated(), check whether
> the cluster containing a delalloc block to be added has been delayed or
> allocated, no logic changes.
> 
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>

I have one suggestion for improvement here.

> +/*
> + * Check whether the cluster containing lblk has been delayed or allocated,
> + * if not, it means we should reserve a cluster when add delalloc, return 1,
> + * otherwise return 0 or error code.
> + */
> +static int ext4_da_check_clu_allocated(struct inode *inode, ext4_lblk_t lblk,
> +				       bool *allocated)

The name of the function does not quite match what it is returning and that
is confusing. Essentially we have three states here:

a) cluster allocated
b) cluster has delalloc reservation
c) cluster doesn't have either

So maybe we could call the function ext4_clu_alloc_state() and return 0 /
1 / 2 based on the state?

								Honza

> +{
> +	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> +	int ret;
> +
> +	*allocated = false;
> +	if (ext4_es_scan_clu(inode, &ext4_es_is_delonly, lblk))
> +		return 0;
> +
> +	if (ext4_es_scan_clu(inode, &ext4_es_is_mapped, lblk))
> +		goto allocated;
> +
> +	ret = ext4_clu_mapped(inode, EXT4_B2C(sbi, lblk));
> +	if (ret < 0)
> +		return ret;
> +	if (ret == 0)
> +		return 1;
> +allocated:
> +	*allocated = true;
> +	return 0;
> +}
> +
>  /*
>   * ext4_insert_delayed_block - adds a delayed block to the extents status
>   *                             tree, incrementing the reserved cluster/block
> @@ -1682,23 +1710,13 @@ static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk)
>  		if (ret != 0)   /* ENOSPC */
>  			return ret;
>  	} else {   /* bigalloc */
> -		if (!ext4_es_scan_clu(inode, &ext4_es_is_delonly, lblk)) {
> -			if (!ext4_es_scan_clu(inode,
> -					      &ext4_es_is_mapped, lblk)) {
> -				ret = ext4_clu_mapped(inode,
> -						      EXT4_B2C(sbi, lblk));
> -				if (ret < 0)
> -					return ret;
> -				if (ret == 0) {
> -					ret = ext4_da_reserve_space(inode, 1);
> -					if (ret != 0)   /* ENOSPC */
> -						return ret;
> -				} else {
> -					allocated = true;
> -				}
> -			} else {
> -				allocated = true;
> -			}
> +		ret = ext4_da_check_clu_allocated(inode, lblk, &allocated);
> +		if (ret < 0)
> +			return ret;
> +		if (ret > 0) {
> +			ret = ext4_da_reserve_space(inode, 1);
> +			if (ret != 0)   /* ENOSPC */
> +				return ret;
>  		}
>  	}
>  
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR