Re: [f2fs-dev] [PATCH RESEND 2/5] f2fs: only initialize largest extent without extent_node at inode init

[Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On 6/12/26 19:58, Yongpeng Yang wrote:
> From: Yongpeng Yang <yangyongpeng@xiaomi.com>
> 
> The largest extent takes effect during both read mapping and write
> mapping lookups, while read mapping does not need to access the
> extent_node. For write mapping, the case where the largest extent is
> not in the extent tree can already be handled by the merge logic, and
> cases that cannot be merged do not require the largest extent to
> participate either.
> 
> Therefore, the largest extent does not need to initialize a
> corresponding extent_node, reducing memory footprint.
> 
> Signed-off-by: Yongpeng Yang <yangyongpeng@xiaomi.com>
> ---
>  fs/f2fs/extent_cache.c | 18 +-----------------
>  1 file changed, 1 insertion(+), 17 deletions(-)
> 
> diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
> index aa368a01b035..f8d94db60dc6 100644
> --- a/fs/f2fs/extent_cache.c
> +++ b/fs/f2fs/extent_cache.c
> @@ -410,10 +410,8 @@ static void __drop_largest_extent(struct extent_tree *et,
>  void f2fs_init_read_extent_tree(struct inode *inode, struct folio *ifolio)
>  {
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> -	struct extent_tree_info *eti = &sbi->extent_tree[EX_READ];
>  	struct f2fs_extent *i_ext = &F2FS_INODE(ifolio)->i_ext;
>  	struct extent_tree *et;
> -	struct extent_node *en;
>  	struct extent_info ei = {0};
>  
>  	if (!__may_extent_tree(inode, EX_READ)) {
> @@ -435,21 +433,7 @@ void f2fs_init_read_extent_tree(struct inode *inode, struct folio *ifolio)
>  	if (atomic_read(&et->node_cnt) || !ei.len)
>  		goto skip;
>  
> -	if (IS_DEVICE_ALIASING(inode)) {
> -		et->largest = ei;
> -		goto skip;
> -	}
> -
> -	en = __attach_extent_node(sbi, et, &ei, NULL,
> -				&et->root.rb_root.rb_node, true);
> -	if (en) {
> -		et->largest = en->ei;
> -		et->cached_en = en;
> -
> -		spin_lock(&eti->extent_lock);
> -		list_add_tail(&en->list, &eti->extent_list);
> -		spin_unlock(&eti->extent_lock);
> -	}
> +	et->largest = ei;

Previously, we can split largest extent node to two if we punched it, now
we can not? IIUC.

Thanks,

>  skip:
>  	/* Let's drop, if checkpoint got corrupted. */
>  	if (f2fs_cp_error(sbi)) {



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