Re: [PATCH v2] generic/402: Make timestamp range check conditional

[Eryu Guan <guaneryu@gmail.com>]

On Mon, Dec 30, 2019 at 09:34:47AM +0200, Amir Goldstein wrote:
> On Sun, Dec 29, 2019 at 12:13 AM Deepa Dinamani <deepa.kernel@gmail.com> wrote:
> >
> > Addition of fs-specific timestamp range checking was added
> > in 188d20bcd1eb ("vfs: Add file timestamp range support").
> >
> > Add a check for whether the kernel supports the limits check
> > before running the associated test.
> >
> > ext4 has been chosen to test for the presence of kernel support
> > for this feature. If there is a concern that ext4 could be built
> > out of the kernel, I can include a _require_ext4() along the
> > lines of _require_ext2().
> >
> > Suggested-by: Amir Goldstein <amir73il@gmail.com>
> > Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>

Sorry for chiming in so late..

> > ---
> > * Changes since v1:
> >   used loopback device instead of mkfs scratch dev
> >
> >  common/rc         | 26 ++++++++++++++++++++++++++
> >  tests/generic/402 |  3 +++
> >  2 files changed, 29 insertions(+)
> >
> > diff --git a/common/rc b/common/rc
> > index 816588d6..6248adf7 100644
> > --- a/common/rc
> > +++ b/common/rc
> > @@ -1981,6 +1981,32 @@ _run_aiodio()
> >      return $status
> >  }
> >
> > +_require_kernel_timestamp_range()
> > +{
> > +       LOOP_FILE=$SCRATCH_MNT/loop_file
> > +       LOOP_MNT=$SCRATCH_MNT/loop_mnt
> > +
> > +       dd if=/dev/zero of=$LOOP_FILE bs=1M count=2 2>&1 | _filter_dd || _fail "loopback prep failed"
> > +
> > +       # Use ext4 with 128-byte inodes, which do not have room for extended timestamp
> > +       FSTYP=ext4 MKFS_OPTIONS=-I128 \
> > +       _mkfs_dev $LOOP_FILE >> $seqres.full 2>&1 || _fail "ext4 mkfs failed"
> > +
> > +       LOOP_DEV=$(_create_loop_device $LOOP_FILE)
> > +       mkdir -p $LOOP_MNT >> $seqres.full 2>&1 || _fail "failed to create $LOOP_MNT"
> > +       mount -t ext4 ${LOOP_DEV} ${LOOP_MNT} >> $seqres.full 2>&1 || _fail "ext4 mount failed"
> > +       notrun=false
> > +       _check_dmesg_for "ext4 filesystem being mounted at ${LOOP_MNT} supports timestamps until 2038" || \
> > +               notrun=true
> > +
> > +       umount ${LOOP_MNT} >> $seqres.full 2>&1 ||_fail "failed to umount $LOOP_MNT"
> > +       _destroy_loop_device ${LOOP_DEV} >> $seqres.full 2>&1
> > +
> > +       if $notrun; then
> > +               _notrun "Kernel does not support timestamp limits"
> > +       fi
> > +}
> > +
> 
> As a generic helper, this function has a few problems:
> 1. It assumes scratch dev is mounted (and you're not even calling it
> after _scratch_mount)
> 2. The cleanup() hook won't clean loop mnt/dev if interrupted
> 3. test doesn't have _require_loop (nor require ext4 as you mentioned)
> 
> All this leads me to think that perhaps it would be better off, at least until
> kernel has fsinfo, to keep this entire helper inside generic/402,
> while addressing
> the issues above in the test itself.
> 
> A more generic solution would be harder and IMO and overkill at this point.
> 
> What do you think?

After reading through this thread, I prefer waiting for the comming
fsinfo interface, detecting the timestamp limit support using ext2 &
loop device doesn't look "pretty" and is just a temporary solution.

Thanks,
Eryu