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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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