linux-kernel - Re: [PATCH] f2fs: don't traverse directory blocks after EOF

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Message-ID: <c2b7d0cd-ea10-4e25-829c-53967927bd03@kernel.org>
Date: Fri, 26 Jul 2024 09:06:11 +0800
From: Chao Yu <chao@...nel.org>
To: Jaegeuk Kim <jaegeuk@...nel.org>
Cc: linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: don't traverse directory blocks after EOF

On 2024/7/26 0:55, Jaegeuk Kim wrote:
> On 07/12, Chao Yu wrote:
>> All directory blocks are within the scope of i_size, so let's limit
>> the end_block to just check valid dirent blocks.
> 
> Do we really need this?

f2fs_readdir() and f2fs_empty_dir() uses dir_blocks() for upper boundary,
this patch aligns find_in_level() w/ them.

Also, it can avoid grabbing never used page cache across EOF.

So, we can consider taking this patch?

Thanks,

> 
>>
>> Meanwhile, it uses dir_blocks() instead of variable for cleanup in
>> __f2fs_find_entry().
>>
>> Signed-off-by: Chao Yu <chao@...nel.org>
>> ---
>>   fs/f2fs/dir.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
>> index 02c9355176d3..d4591c215f07 100644
>> --- a/fs/f2fs/dir.c
>> +++ b/fs/f2fs/dir.c
>> @@ -305,18 +305,21 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir,
>>   	int s = GET_DENTRY_SLOTS(fname->disk_name.len);
>>   	unsigned int nbucket, nblock;
>>   	unsigned int bidx, end_block;
>> +	unsigned long last_block;
>>   	struct page *dentry_page;
>>   	struct f2fs_dir_entry *de = NULL;
>>   	pgoff_t next_pgofs;
>>   	bool room = false;
>>   	int max_slots;
>>   
>> +	last_block = dir_blocks(dir);
>>   	nbucket = dir_buckets(level, F2FS_I(dir)->i_dir_level);
>>   	nblock = bucket_blocks(level);
>>   
>>   	bidx = dir_block_index(level, F2FS_I(dir)->i_dir_level,
>>   			       le32_to_cpu(fname->hash) % nbucket);
>>   	end_block = bidx + nblock;
>> +	end_block = min_t(unsigned int, end_block, last_block);
>>   
>>   	while (bidx < end_block) {
>>   		/* no need to allocate new dentry pages to all the indices */
>> @@ -361,7 +364,6 @@ struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
>>   					 const struct f2fs_filename *fname,
>>   					 struct page **res_page)
>>   {
>> -	unsigned long npages = dir_blocks(dir);
>>   	struct f2fs_dir_entry *de = NULL;
>>   	unsigned int max_depth;
>>   	unsigned int level;
>> @@ -373,7 +375,7 @@ struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
>>   		goto out;
>>   	}
>>   
>> -	if (npages == 0)
>> +	if (dir_blocks(dir) == 0)
>>   		goto out;
>>   
>>   	max_depth = F2FS_I(dir)->i_current_depth;
>> -- 
>> 2.40.1