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

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Date:   Fri, 10 Jul 2020 12:17:46 +0900
From:   Daeho Jeong <daeho43@...il.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
        Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: change the way of handling range.len in F2FS_IOC_SEC_TRIM_FILE

1. The valid data will be within i_size.
2. All the trim operations will be done in a unit of block, even if
i_size is not aligned with BLKSIZE like the below.

        index = F2FS_BYTES_TO_BLK(range.start);
        pg_end = DIV_ROUND_UP(end_addr, F2FS_BLKSIZE);     <= BLKSIZE aligned

Are you worried about the case that sudden power-off occurs while a
file is being truncated?
ex) 1GB file is being truncated to 4KB -> sudden power-off ->
i_size(4KB), i_blocks(maybe somewhere between 4KB and 1GB)

2020년 7월 10일 (금) 오후 12:02, Jaegeuk Kim <jaegeuk@...nel.org>님이 작성:
>
> 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;
>
> Hmm, what if there are blocks beyond i_size? Do we need to check i_blocks for
> 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