Re: [f2fs-dev] [PATCH] f2fs: change the way of handling range.len in F2FS_IOC_SEC_TRIM_FILE

[Chao Yu <yuchao0@huawei.com>]

On 2020/7/10 11:31, Jaegeuk Kim wrote:
> On 07/10, Chao Yu wrote:
>> On 2020/7/10 11:02, Jaegeuk Kim wrote:
>>> On 07/10, Daeho Jeong wrote:
>>>> From: Daeho Jeong <daehojeong@google.com>
>>>>
>>>> Changed the way of handling range.len of F2FS_IOC_SEC_TRIM_FILE.
>>>>  1. Added -1 value support for range.len to signify the end of file.
>>>>  2. If the end of the range passes over the end of file, it means until
>>>>     the end of file.
>>>>  3. ignored the case of that range.len is zero to prevent the function
>>>>     from making end_addr zero and triggering different behaviour of
>>>>     the function.
>>>>
>>>> Signed-off-by: Daeho Jeong <daehojeong@google.com>
>>>> ---
>>>>  fs/f2fs/file.c | 16 +++++++---------
>>>>  1 file changed, 7 insertions(+), 9 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>> index 368c80f8e2a1..1c4601f99326 100644
>>>> --- a/fs/f2fs/file.c
>>>> +++ b/fs/f2fs/file.c
>>>> @@ -3813,21 +3813,19 @@ static int f2fs_sec_trim_file(struct file *filp, unsigned long arg)
>>>>  	file_start_write(filp);
>>>>  	inode_lock(inode);
>>>>  
>>>> -	if (f2fs_is_atomic_file(inode) || f2fs_compressed_file(inode)) {
>>>> +	if (f2fs_is_atomic_file(inode) || f2fs_compressed_file(inode) ||
>>>> +			range.start >= inode->i_size) {
>>>>  		ret = -EINVAL;
>>>>  		goto err;
>>>>  	}
>>>>  
>>>> -	if (range.start >= inode->i_size) {
>>>> -		ret = -EINVAL;
>>>> +	if (range.len == 0)
>>>>  		goto err;
>>>> -	}
>>>>  
>>>> -	if (inode->i_size - range.start < range.len) {
>>>> -		ret = -E2BIG;
>>>> -		goto err;
>>>> -	}
>>>> -	end_addr = range.start + range.len;
>>>> +	if (range.len == (u64)-1 || inode->i_size - range.start < range.len)
>>>> +		end_addr = inode->i_size;
>>
>> We can remove 'range.len == (u64)-1' condition since later condition can cover
>> this?
>>
>>>
>>> Hmm, what if there are blocks beyond i_size? Do we need to check i_blocks for
>>
>> The blocks beyond i_size will never be written, there won't be any valid message
>> there, so we don't need to worry about that.
> 
> I don't think we have a way to guarantee the order of i_size and block
> allocation in f2fs. See f2fs_write_begin and f2fs_write_end.

However, write_begin & write_end are covered by inode_lock, it could not be
racy with inode size check in f2fs_sec_trim_file() as it hold inode_lock as
well?

> 
>>
>> Thanks,
>>
>>> ending criteria?
>>>
>>>> +	else
>>>> +		end_addr = range.start + range.len;
>>>>  
>>>>  	to_end = (end_addr == inode->i_size);
>>>>  	if (!IS_ALIGNED(range.start, F2FS_BLKSIZE) ||
>>>> -- 
>>>> 2.27.0.383.g050319c2ae-goog
>>>>
>>>>
>>>>
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>>>
>>>
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>>> .
>>>
> .
>