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Message-ID: <5qdt2outacmgyrz4w5lqokwhp3haifs5z22hrgg22fd4kgbyzt@2y54npfzwwzv>
Date: Wed, 8 Oct 2025 13:28:57 +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, 
	yi.zhang@...wei.com, libaokun1@...wei.com, yukuai3@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH v2 04/13] ext4: make ext4_es_lookup_extent() pass out the
 extent seq counter

On Thu 25-09-25 17:26:00, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
> 
> When querying extents in the extent status tree, we should hold the
> data_sem if we want to obtain the sequence number as a valid cookie
> simultaneously. However, currently, ext4_map_blocks() calls
> ext4_es_lookup_extent() without holding data_sem. Therefore, we should
> acquire i_es_lock instead, which also ensures that the sequence cookie
> and the extent remain consistent. Consequently, make
> ext4_es_lookup_extent() to pass out the sequence number when necessary.
> 
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>

Looks good. Feel free to add:

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

								Honza

> ---
>  fs/ext4/extents.c        | 2 +-
>  fs/ext4/extents_status.c | 6 ++++--
>  fs/ext4/extents_status.h | 2 +-
>  fs/ext4/inode.c          | 8 ++++----
>  4 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index ca5499e9412b..c7d219e6c6d8 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -2213,7 +2213,7 @@ static int ext4_fill_es_cache_info(struct inode *inode,
>  	while (block <= end) {
>  		next = 0;
>  		flags = 0;
> -		if (!ext4_es_lookup_extent(inode, block, &next, &es))
> +		if (!ext4_es_lookup_extent(inode, block, &next, &es, NULL))
>  			break;
>  		if (ext4_es_is_unwritten(&es))
>  			flags |= FIEMAP_EXTENT_UNWRITTEN;
> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index 62886e18e2a3..9bf2f48d8ffe 100644
> --- a/fs/ext4/extents_status.c
> +++ b/fs/ext4/extents_status.c
> @@ -1035,8 +1035,8 @@ void ext4_es_cache_extent(struct inode *inode, ext4_lblk_t lblk,
>   * Return: 1 on found, 0 on not
>   */
>  int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
> -			  ext4_lblk_t *next_lblk,
> -			  struct extent_status *es)
> +			  ext4_lblk_t *next_lblk, struct extent_status *es,
> +			  u64 *pseq)
>  {
>  	struct ext4_es_tree *tree;
>  	struct ext4_es_stats *stats;
> @@ -1095,6 +1095,8 @@ int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
>  			} else
>  				*next_lblk = 0;
>  		}
> +		if (pseq)
> +			*pseq = EXT4_I(inode)->i_es_seq;
>  	} else {
>  		percpu_counter_inc(&stats->es_stats_cache_misses);
>  	}
> diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h
> index 8f9c008d11e8..f3396cf32b44 100644
> --- a/fs/ext4/extents_status.h
> +++ b/fs/ext4/extents_status.h
> @@ -148,7 +148,7 @@ extern void ext4_es_find_extent_range(struct inode *inode,
>  				      struct extent_status *es);
>  extern int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
>  				 ext4_lblk_t *next_lblk,
> -				 struct extent_status *es);
> +				 struct extent_status *es, u64 *pseq);
>  extern bool ext4_es_scan_range(struct inode *inode,
>  			       int (*matching_fn)(struct extent_status *es),
>  			       ext4_lblk_t lblk, ext4_lblk_t end);
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 5b7a15db4953..c7fac4b89c88 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -649,7 +649,7 @@ static int ext4_map_create_blocks(handle_t *handle, struct inode *inode,
>  	 * extent status tree.
>  	 */
>  	if (flags & EXT4_GET_BLOCKS_PRE_IO &&
> -	    ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
> +	    ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es, NULL)) {
>  		if (ext4_es_is_written(&es))
>  			return retval;
>  	}
> @@ -723,7 +723,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
>  		ext4_check_map_extents_env(inode);
>  
>  	/* Lookup extent status tree firstly */
> -	if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
> +	if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es, NULL)) {
>  		if (ext4_es_is_written(&es) || ext4_es_is_unwritten(&es)) {
>  			map->m_pblk = ext4_es_pblock(&es) +
>  					map->m_lblk - es.es_lblk;
> @@ -1908,7 +1908,7 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map)
>  	ext4_check_map_extents_env(inode);
>  
>  	/* Lookup extent status tree firstly */
> -	if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
> +	if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es, NULL)) {
>  		map->m_len = min_t(unsigned int, map->m_len,
>  				   es.es_len - (map->m_lblk - es.es_lblk));
>  
> @@ -1961,7 +1961,7 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map)
>  	 * is held in write mode, before inserting a new da entry in
>  	 * the extent status tree.
>  	 */
> -	if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
> +	if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es, NULL)) {
>  		map->m_len = min_t(unsigned int, map->m_len,
>  				   es.es_len - (map->m_lblk - es.es_lblk));
>  
> -- 
> 2.46.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR

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