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

On 6/15/26 7:55 PM, Chao Yu via Linux-f2fs-devel wrote:
> On 6/12/26 19:58, Yongpeng Yang wrote:
>> From: Yongpeng Yang <[email protected]>
>>
>> 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 <[email protected]>
>> ---
>>   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.

Prior to this change, the largest extent could also be shrunk, so the
set of scenarios that need handling during punch remains identical
before and after the modification.

For the largest extent, it only needs to guarantee that the mapping
information it records stays consistent with the mappings tracked in the
extent tree and multi-level indirect indices. The punch operation does
not break this consistency. Moreover, the largest extent is not required
to be the longest extent among all entries in the extent tree. It merely
needs to match the mappings stored in multi-level indirect indices and
be no smaller than the maximum extent present in the extent tree.

Thanks
Yongpeng,


> 
> Thanks,
> 
>>   skip:
>>   	/* Let's drop, if checkpoint got corrupted. */
>>   	if (f2fs_cp_error(sbi)) {
> 
> 
> 
> _______________________________________________
> Linux-f2fs-devel mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel



_______________________________________________
Linux-f2fs-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel