On Tue, Sep 3, 2024 at 6:21 AM Zorro Lang <zlang@xxxxxxxxxx> wrote:
>
> On Fri, Aug 30, 2024 at 08:08:44PM +0200, Amir Goldstein wrote:
> > Test overlayfs over xfs with and without "volatile" mount option.
> >
> > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> > ---
> >
> > Zorro,
> >
> > I was going to make a generic test from xfs/546, so that overlayfs could
> > also run it, but then I realized that ext4 does not behave as xfs in
> > that case (it returns success on syncfs post shutdown).
> >
> > Unless and until this behavior is made a standard, I made an overlayfs
> > specialized test instead, which checks for underlying fs xfs.
> > While at it, I also added test coverage for the "volatile" mount options
> > that is expected to return succuss in that case regardles of the
> > behavior of the underlying fs.
> >
> > Thanks,
> > Amir.
> >
> > tests/overlay/087 | 62 +++++++++++++++++++++++++++++++++++++++++++
> > tests/overlay/087.out | 4 +++
> > 2 files changed, 66 insertions(+)
> > create mode 100755 tests/overlay/087
> > create mode 100644 tests/overlay/087.out
> >
> > diff --git a/tests/overlay/087 b/tests/overlay/087
> > new file mode 100755
> > index 00000000..a5afb0d5
> > --- /dev/null
> > +++ b/tests/overlay/087
> > @@ -0,0 +1,62 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Copyright (c) 2022 Oracle. All Rights Reserved.
> > +# Copyright (c) 2024 CTERA Networks. All Rights Reserved.
> > +#
> > +# FS QA Test No. 087
> > +#
> > +# This is a variant of test xfs/546 for overlayfs
> > +# with and without the "volatile" mount option.
> > +# It only works over xfs underlying fs.
> > +#
> > +# Regression test for kernel commits:
> > +#
> > +# 5679897eb104 ("vfs: make sync_filesystem return errors from ->sync_fs")
> > +# 2d86293c7075 ("xfs: return errors in xfs_fs_sync_fs")
> > +#
> > +# During a code inspection, I noticed that sync_filesystem ignores the return
> > +# value of the ->sync_fs calls that it makes. sync_filesystem, in turn is used
> > +# by the syncfs(2) syscall to persist filesystem changes to disk. This means
> > +# that syncfs(2) does not capture internal filesystem errors that are neither
> > +# visible from the block device (e.g. media error) nor recorded in s_wb_err.
> > +# XFS historically returned 0 from ->sync_fs even if there were log failures,
> > +# so that had to be corrected as well.
> > +#
> > +# The kernel commits above fix this problem, so this test tries to trigger the
> > +# bug by using the shutdown ioctl on a clean, freshly mounted filesystem in the
> > +# hope that the EIO generated as a result of the filesystem being shut down is
> > +# only visible via ->sync_fs.
> > +#
> > +. ./common/preamble
> > +_begin_fstest auto quick mount shutdown
> > +
> > +
> > +# Modify as appropriate.
> > +_require_xfs_io_command syncfs
> > +_require_scratch_nocheck
> > +_require_scratch_shutdown
> > +
> > +[ "$OVL_BASE_FSTYP" == "xfs" ] || \
> > + _notrun "base fs $OVL_BASE_FSTYP has unknown behavior with syncfs after shutdown"
> > +
> > +# Reuse the fs formatted when we checked for the shutdown ioctl, and don't
> > +# bother checking the filesystem afterwards since we never wrote anything.
> > +echo "=== syncfs after shutdown"
> > +_scratch_mount
> > +# This command is complicated a bit because in the case of overlayfs the
> > +# syncfs fd needs to be opened before shutdown and it is different from the
> > +# shutdown fd, so we cannot use the _scratch_shutdown() helper.
> > +# Filter out xfs_io output of active fds.
> > +$XFS_IO_PROG -x -c "open $(_scratch_shutdown_handle)" -c 'shutdown -f ' -c close -c syncfs $SCRATCH_MNT | \
> > + grep -vF '[00'
> > +
> > +# Now repeat the same test with a volatile overlayfs mount and expect no error
> > +_scratch_unmount
> > +echo "=== syncfs after shutdown (volatile)"
> > +_scratch_mount -o volatile
> > +$XFS_IO_PROG -x -c "open $(_scratch_shutdown_handle)" -c 'shutdown -f ' -c close -c syncfs $SCRATCH_MNT | \
> > + grep -vF '[00'
>
> Oh, the test steps are much different from xfs/546. If we move x/546 to generic/,
> can overlay reproduce this bug by that?
Yes and no.
For overlayfs to support this as a generic test, the helper
_scratch_shutdown_handle must be used and the shutdown+syncfs
command must be complicated to something like this:
$XFS_IO_PROG -x -c "open $(_scratch_shutdown_handle)" -c 'shutdown -f
' -c close -c syncfs $SCRATCH_MNT | \
grep -vF '[00'
This is because overlayfs itself does not support the shutdown ioctl.
If the test is moved to generic as it is we get an error when running
overlayfs:
XFS_IOC_GOINGDOWN: Inappropriate ioctl for device
because _require_scratch_shutdown is "supported" by overlayfs
but only when the _scratch_shutdown helpers are used.
If the test is to be moved as is, it will need to opt-out of overlayfs
explicitly.
> If not, I think we can have this overlay
> specific test case at first, and "move x/546 to generic" can be another job.
>
The reason I posted the overlayfs test is because for a while I noticed
that we do not have test coverage for "volatile" mount option
and adding this test coverage to this test was a very low hanging fruit.
So I would like to keep the overlayfs test regardless of the decision
about moving x/546 to generic.
Thanks,
Amir.
