linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: change the way of handling range.len in F2FS_IOC_SEC_TRIM

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Date:   Thu, 9 Jul 2020 20:52:15 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     Daeho Jeong <daeho43@...il.com>,
        Daeho Jeong <daehojeong@...gle.com>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: change the way of handling range.len in
 F2FS_IOC_SEC_TRIM_FILE

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@...gle.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@...gle.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.

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