Re: [PATCH] overlay: add test for rename of lower symlink with NOATIME attr

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On Wed, Sep 20, 2023 at 06:34:21PM +0300, Amir Goldstein wrote:
> On Wed, Sep 20, 2023 at 6:14 PM Zorro Lang <zlang@xxxxxxxxxx> wrote:
> >
> > On Wed, Sep 20, 2023 at 04:03:55PM +0300, Amir Goldstein wrote:
> > > A test for a regression from v5.15 reported by Ruiwen Zhao:
> > > https://lore.kernel.org/linux-unionfs/CAKd=y5Hpg7J2gxrFT02F94o=FM9QvGp=kcH1Grctx8HzFYvpiA@xxxxxxxxxxxxxx/

Could you give one more sentence to tell what kind of regression
does this case test for? Not only a link address.

> > >
> > > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> > > ---
> > >
> > > Zorro,
> > >
> > > This is a test for a regression in kernel v5.15.
> > > The fix was merged for 6.6-rc2 and has been picked for
> > > the upcoming LTS releases 5.15, 6.1, 6.5.
> > >
> > > The reproducer only manifests the bug in fs that inherit noatime flag,
> > > namely ext4, btrfs, ... but not xfs.
> > >
> > > The test does _notrun on xfs for that reason.
> > >
> > > Thanks,
> > > Amir.
> > >
> > >  tests/overlay/082     | 68 +++++++++++++++++++++++++++++++++++++++++++
> > >  tests/overlay/082.out |  2 ++
> > >  2 files changed, 70 insertions(+)
> > >  create mode 100755 tests/overlay/082
> > >  create mode 100644 tests/overlay/082.out
> > >
> > > diff --git a/tests/overlay/082 b/tests/overlay/082
> > > new file mode 100755
> > > index 00000000..abea3c2b
> > > --- /dev/null
> > > +++ b/tests/overlay/082
> > > @@ -0,0 +1,68 @@
> > > +#! /bin/bash
> > > +# SPDX-License-Identifier: GPL-2.0
> > > +# Copyright (C) 2023 CTERA Networks. All Rights Reserved.
> > > +#
> > > +# FS QA Test 082
> > > +#
> > > +# kernel commit 72db82115d2b ("ovl: copy up sync/noatime fileattr flags")
> > > +# from v5.15 introduced a regression.

Hi Amir,

Thanks for this new regression test. More detailed (picky:) review points
as below ...

So this commit is the one which introduced a regression. But we generally
say what kind of regression does this case test for, in this comment.

> > > +#
> > > +. ./common/preamble
> > > +_begin_fstest auto quick

According the source code of this case, please think about more detailed group
names, likes: "symlink", "copyup" and "atime".

> > > +
> > > +# Import common functions.
> > > +. ./common/filter

I think this case doesn't use any filter helpers, right?

> > > +
> > > +# real QA test starts here
> > > +_supported_fs overlay
> > > +_fixed_by_kernel_commit ab048302026d \
> > > +     "ovl: fix failed copyup of fileattr on a symlink"
> > > +
> > > +_require_scratch
> > > +_require_chattr A
> > > +
> > > +# remove all files from previous runs
> > > +_scratch_mkfs
> > > +
> > > +# prepare lower test dir with NOATIME flag
> > > +lowerdir=$OVL_BASE_SCRATCH_MNT/$OVL_LOWER
> > > +mkdir -p $lowerdir/testdir
> > > +$CHATTR_PROG +A $lowerdir/testdir >> $seqres.full 2>&1 ||
> > > +     _notrun "base fs $OVL_BASE_FSTYP does not support No_Atime flag"
> > > +
> > > +# The NOATIME is inheritted to children symlink in ext4/fs2fs
> > > +# (and on tmpfs on recent kernels).
> > > +# The overlayfs test will not fail unless base fs is
> > > +# one of those filesystems.
> > > +#
> > > +# The problem with this inheritence is that the NOATIME flag is inheritted
> > > +# to a symlink and the flag does take effect, but there is no way to query
> > > +# the flag (lsattr) or change it (chattr) on a symlink, so overlayfs will
> > > +# fail when trying to copy up NOATIME flag from lower to upper symlink.
> > > +#
> > > +touch $lowerdir/testdir/foo
> > > +ln -sf foo $lowerdir/testdir/lnk
> > > +
> > > +$LSATTR_PROG -l $lowerdir/testdir/foo >> $seqres.full 2>&1
> > > +$LSATTR_PROG -l $lowerdir/testdir/foo | grep -q No_Atime || \
> > > +     _notrun "base fs $OVL_BASE_FSTYP does not inherit No_Atime flag"
> > > +
> > > +before=$(stat -c %x $lowerdir/testdir/lnk)
> > > +echo "symlink atime before readlink: $before" >> $seqres.full 2>&1

I remember some filesystems' timestamp for atime (e.g. exfat) might have more
seconds granularity. So it would be better to `sleep 2s` at here.

Correct me if someone fs need more or less :)

> > > +cat $lowerdir/testdir/lnk
> > > +after=$(stat -c %x $lowerdir/testdir/lnk)
> > > +echo "symlink atime after readlink: $after" >> $seqres.full 2>&1
> > > +
> > > +[ "$before" == "$after" ] || \
> > > +     _notrun "base fs $OVL_BASE_FSTYP does not inherit No_Atime flag on symlink"
> > > +
> > > +# mounting overlay
> > > +_scratch_mount
> > > +
> > > +# moving symlink will try to copy up lower symlink flags
> > > +mv $SCRATCH_MNT/testdir/lnk $SCRATCH_MNT/
> >
> > Lots of above codes are checking if the underlying fs supports No_Atime (and inherit),
> > and _notrun if not support. How about do these checking steps in a require_*
> > function locally or in common/, likes _require_noatime_inheritance(). And we also
> > can let _require_chattr accept one more argument to specify a test directory.
> >
> 
> ok.
> 
> > The "mv ..." command looks like the final testing step. If there's not that bug,
> > nothing happen, but I'm wondering what should happen if there's a bug?
> 
> mv fails with error ENXIO, see linked bug report in commit message.

Thanks, I think we can add "fails with error ENXIO at here, if the bug is reproduced" in
the comment of that "mv ..." command.

Thanks,
Zorro

> 
> Thanks,
> Amir.
> 




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