Re: [PATCH 5.10 CANDIDATE 7/8] xfs: consider shutdown in bmapbt cursor delete assert

Amir Goldstein
2022-06-03T09:40:08Z

On Thu, Jun 2, 2022 at 8:55 AM Amir Goldstein <amir73il@gmail.com> wrote:
>
> On Thu, Jun 2, 2022 at 8:15 AM Dave Chinner <david@fromorbit.com> wrote:
> >
> > On Thu, Jun 02, 2022 at 07:24:26AM +0300, Amir Goldstein wrote:
> > > On Thu, Jun 2, 2022 at 3:38 AM Dave Chinner <david@fromorbit.com> wrote:
> > > >
> > > > On Wed, Jun 01, 2022 at 01:45:46PM +0300, Amir Goldstein wrote:
> > > > > From: Brian Foster <bfoster@redhat.com>
> > > > >
> > > > > commit 1cd738b13ae9b29e03d6149f0246c61f76e81fcf upstream.
> > > > >
> > > > > The assert in xfs_btree_del_cursor() checks that the bmapbt block
> > > > > allocation field has been handled correctly before the cursor is
> > > > > freed. This field is used for accurate calculation of indirect block
> > > > > reservation requirements (for delayed allocations), for example.
> > > > > generic/019 reproduces a scenario where this assert fails because
> > > > > the filesystem has shutdown while in the middle of a bmbt record
> > > > > insertion. This occurs after a bmbt block has been allocated via the
> > > > > cursor but before the higher level bmap function (i.e.
> > > > > xfs_bmap_add_extent_hole_real()) completes and resets the field.
> > > > >
> > > > > Update the assert to accommodate the transient state if the
> > > > > filesystem has shutdown. While here, clean up the indentation and
> > > > > comments in the function.
> > > > >
> > > > > Signed-off-by: Brian Foster <bfoster@redhat.com>
> > > > > Reviewed-by: Darrick J. Wong <djwong@kernel.org>
> > > > > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> > > > > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > > > > ---
> > > > > fs/xfs/libxfs/xfs_btree.c | 33 ++++++++++++---------------------
> > > > > 1 file changed, 12 insertions(+), 21 deletions(-)
> > > >
> > > > https://git.kernel.org/pub/scm/fs/xfs/xfs-linux.git/commit/?h=for-next&id=56486f307100e8fc66efa2ebd8a71941fa10bf6f
> > > >
> > >
> > > Warm from the over :)
> > >
> > > I will need more time to verify that this new fix is not breaking LTS
> > > but I don't think that it should be blocking taking the old 5.12 fix now.
> > > Right?
> >
> > Rule #1: don't introduce new bugs into stable kernels.
> >
> > This commit has a known (and fixed) bug in it. If you are going to
> > back port it to a stable kernel, then you need to also pull in the
> > fix for that commit, too.
>
> Oh. I misunderstood.
> I thought this wasn't a Fixes: situation.
> I thought you pointed me to another related bug fix.
>

Just to make sure we are all on the same page.

I have applied both patches to my test tree:
1. 1cd738b13ae9 xfs: consider shutdown in bmapbt cursor delete assert
2. 56486f307100 xfs: assert in xfs_btree_del_cursor should take into
account error

Patch #2 looks pretty safe and it only affects builds with XFS_WARN/DEBUG,
so I am not too concerned about a soaking period.
I plan to send it along with patch #1 to stable after a few more test runs.

If my understanding is correct, the ASSERT has been there since git epoc.
The too strict ASSERT was relaxed two times by patch #1 and then by patch #2.

Maybe I am missing something, but I do not see how applying patch #1
introduces a bug, but anyway, I am going to send both patches together.

Thanks,
Amir.