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 20:20:35 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Daeho Jeong <daeho43@...il.com>
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

On 07/10, Daeho Jeong wrote:
> 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)

Yes. Basically, I believe we can have some data beyond i_size like fsverity.

> 
> 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