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From:   Daeho Jeong <daeho43@gmail.com>
Date:   Thu, 9 Jul 2020 13:15:35 +0900
Message-ID: <CACOAw_x7GkM0os2xo+2CX+pysCBb6QbWxxr0jC3C703iFQi+1A@mail.gmail.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: ignore when len of range in
 f2fs_sec_trim_file is zero
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com,
        Daeho Jeong <daehojeong@google.com>
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I thought it's better to treat this as the error case, since the range
already passed out of the i_size range.
If we allow that, the user needs to send the range parameter being
aligned like start:0 and len: roundup(i_size, PAGE_SIZE), even if he
or she wants to erase the whole file.

2020=EB=85=84 7=EC=9B=94 9=EC=9D=BC (=EB=AA=A9) =EC=98=A4=ED=9B=84 12:05, C=
hao Yu <yuchao0@huawei.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> On 2020/7/9 9:57, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@google.com>
> >
> > When end_addr comes to zero, it'll trigger different behaviour.
> > To prevent this, we need to ignore the case of that range.len is
> > zero in the function.
> >
> > Signed-off-by: Daeho Jeong <daehojeong@google.com>
> > ---
> >  fs/f2fs/file.c | 7 +++----
> >  1 file changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index 368c80f8e2a1..98b0a8dbf669 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -3813,15 +3813,14 @@ 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 >=3D inode->i_size) {
> >               ret =3D -EINVAL;
> >               goto err;
> >       }
> >
> > -     if (range.start >=3D inode->i_size) {
> > -             ret =3D -EINVAL;
> > +     if (range.len =3D=3D 0)
> >               goto err;
> > -     }
> >
> >       if (inode->i_size - range.start < range.len) {
> >               ret =3D -E2BIG;
>
> How about the case trimming last partial written block?
>
> i_size =3D 8000
> range.start =3D 4096
> range.len =3D 4096
>
> Do we need to roundup(isize, PAGE_SIZE) before comparison?
>
> Thanks,
>
> >