linux-ext4 - Re: [PATCH v2 9/9] ext4: make ext4_da_map_blocks() buffer

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Date: Mon, 29 Apr 2024 12:27:29 +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 9/9] ext4: make ext4_da_map_blocks() buffer_head
 unaware

On Wed 10-04-24 11:42:03, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
> 
> After calling ext4_da_map_blocks(), a delalloc extent state could be
> distinguished through EXT4_MAP_DELAYED flag in map. So factor out
> buffer_head related handles in ext4_da_map_blocks(), make it
> buffer_head unaware, make it become a common helper, it could be used
> for iomap in the future.
> 
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza


> -		retval = es.es_len - (map->m_lblk - es.es_lblk);
> -		if (retval > map->m_len)
> -			retval = map->m_len;
> -		map->m_len = retval;
> +		map->m_len = min_t(unsigned int, map->m_len,
> +				   es.es_len - (map->m_lblk - es.es_lblk));
>  
>  		if (ext4_es_is_hole(&es))
>  			goto add_delayed;
> @@ -1785,10 +1778,8 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
>  		 * Delayed extent could be allocated by fallocate.
>  		 * So we need to check it.
>  		 */
> -		if (ext4_es_is_delayed(&es) && !ext4_es_is_unwritten(&es)) {
> -			map_bh(bh, inode->i_sb, invalid_block);
> -			set_buffer_new(bh);
> -			set_buffer_delay(bh);
> +		if (ext4_es_is_delonly(&es)) {
> +			map->m_flags |= EXT4_MAP_DELAYED;
>  			return 0;
>  		}
>  
> @@ -1803,7 +1794,7 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
>  #ifdef ES_AGGRESSIVE_TEST
>  		ext4_map_blocks_es_recheck(NULL, inode, map, &orig_map, 0);
>  #endif
> -		return retval;
> +		return 0;
>  	}
>  
>  	/*
> @@ -1817,7 +1808,7 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
>  		retval = ext4_map_query_blocks(NULL, inode, map);
>  	up_read(&EXT4_I(inode)->i_data_sem);
>  	if (retval)
> -		return retval;
> +		return retval < 0 ? retval : 0;
>  
>  add_delayed:
>  	down_write(&EXT4_I(inode)->i_data_sem);
> @@ -1827,10 +1818,8 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
>  	 * whitout holding i_rwsem and folio lock.
>  	 */
>  	if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
> -		retval = es.es_len - (map->m_lblk - es.es_lblk);
> -		if (retval > map->m_len)
> -			retval = map->m_len;
> -		map->m_len = retval;
> +		map->m_len = min_t(unsigned int, map->m_len,
> +				   es.es_len - (map->m_lblk - es.es_lblk));
>  
>  		if (!ext4_es_is_hole(&es)) {
>  			up_write(&EXT4_I(inode)->i_data_sem);
> @@ -1840,18 +1829,14 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
>  		retval = ext4_map_query_blocks(NULL, inode, map);
>  		if (retval) {
>  			up_write(&EXT4_I(inode)->i_data_sem);
> -			return retval;
> +			return retval < 0 ? retval : 0;
>  		}
>  	}
>  
> +	map->m_flags |= EXT4_MAP_DELAYED;
>  	retval = ext4_insert_delayed_blocks(inode, map->m_lblk, map->m_len);
>  	up_write(&EXT4_I(inode)->i_data_sem);
> -	if (retval)
> -		return retval;
>  
> -	map_bh(bh, inode->i_sb, invalid_block);
> -	set_buffer_new(bh);
> -	set_buffer_delay(bh);
>  	return retval;
>  }
>  
> @@ -1871,11 +1856,15 @@ int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
>  			   struct buffer_head *bh, int create)
>  {
>  	struct ext4_map_blocks map;
> +	sector_t invalid_block = ~((sector_t) 0xffff);
>  	int ret = 0;
>  
>  	BUG_ON(create == 0);
>  	BUG_ON(bh->b_size != inode->i_sb->s_blocksize);
>  
> +	if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
> +		invalid_block = ~0;
> +
>  	map.m_lblk = iblock;
>  	map.m_len = 1;
>  
> @@ -1884,10 +1873,17 @@ int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
>  	 * preallocated blocks are unmapped but should treated
>  	 * the same as allocated blocks.
>  	 */
> -	ret = ext4_da_map_blocks(inode, &map, bh);
> -	if (ret <= 0)
> +	ret = ext4_da_map_blocks(inode, &map);
> +	if (ret < 0)
>  		return ret;
>  
> +	if (map.m_flags & EXT4_MAP_DELAYED) {
> +		map_bh(bh, inode->i_sb, invalid_block);
> +		set_buffer_new(bh);
> +		set_buffer_delay(bh);
> +		return 0;
> +	}
> +
>  	map_bh(bh, inode->i_sb, map.m_pblk);
>  	ext4_update_bh_state(bh, map.m_flags);
>  
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR