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SubjectRe: [f2fs-dev] [PATCH] f2fs: change the way of handling range.len in F2FS_IOC_SEC_TRIM_FILE
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On 2020/7/10 11:52, Jaegeuk Kim wrote:
> On 07/10, Chao Yu wrote:
>> 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?
>
> Like Daeho said, write_begin -> checkpoint -> power-cut can give bigger i_blocks
> than i_size.

The path won't, cp only persists reserved block in dnode rather than written
data block in segment, because data will be copied to page cache after write_begin.

I think truncation path could as Daeho said:

1. truncate -> i_size update however blocks wasn't truncated yet -> checkpoint -> recovery
2. truncate failed -> i_size update however partial blocks was truncated -> fsync

>
>>
>>>
>>>>
>>>> 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
>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Linux-f2fs-devel mailing list
>>>>>> Linux-f2fs-devel@lists.sourceforge.net
>>>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Linux-f2fs-devel mailing list
>>>>> Linux-f2fs-devel@lists.sourceforge.net
>>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>>>>> .
>>>>>
>>> .
>>>
> .
>

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